Download 3_conception, fetal development

Pregnancy: genetics,
conception, fetal
development
Conception
union of single egg and sperm, marks the
beginning of the pregnancy
 not at as isolated event but as a part of
sequential process:

– gamete formation (egg and sperm)
– ovulation (release of the egg)
– fertilization (union of the gametes)
– implantation in the uterus
Cell Division. Mitosis
the body cells replicate to yield two cells
with the same genetic makeup as the
parent cell.
 First the cell makes a copy of its DNA;
then it divides, and each daughter cell
receives one copy of the genetic material.
 The purpose of mitotic division is for
growth and development or cell
replacement.

Cell Division. Meiosis

The process by which germ cells divide and
decrease their chromosomal number by half and
produces gametes:
– sperm in males
– eggs in females
Human body cells contain 46 chromosomes
(diploid)
 Gametes contain 23 chromosomes (haploid)

Cell Division. Mitosis vs Meiosis
Gametogenesis: Spermatogenesis
 Begins
at puberty (400 million/day)
 Mitotic division of 1 diploid
spermatogonium (primitive sperm cell):
– produces 2 daughter cells Primary
spermatocyte
– contains diploid number of chromosomes
– The cell has already copied its DNA before
devision, so four alleles for each gene are
present. The cell is still considered diploid
because the copies are bound together (one
allele plus its copy on each chromosomes)
I
mitotic division
– Secondary spermatocytes
– contains 23 chromosomes one contains
the X chromosome (plus its copy)
and the other the Y chromosome
(plus its copy).
Gametogenesis: Spermatogenesis
 II
mitotic division
–Spermatids (haploid)
–two gametes with an X chromosome
– two gametes with a Y chromosome
all
of which will
–develop into viable sperm
 Each primary spermatocyte:
– produces 4 spermatozoa
Gametogenesis

Spermatogenesis
primary spermatocytes (46)
2 haploid secondary spermatocyte(22X+22Y)
4 Spermatids
Gametogenesis: Oogenesis

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Begins during fetal life in the
female
All cells contained in the ovaries
at birth
The majority of the estimated 2
million primary oocytes (the cells
that undergo the first meiotic
division) degenerate
spontaneously.
Only 400 to 500 ova will mature
during the approximately 35 years
of a woman's reproductive life.
Gametogenesis: Oogenesis

Oogonia (stem cells of females)
complete mitotic divisions between
third and seventh months gestation:
– primary oocytes replicate their DNA but
remain suspended at this stage until puberty

Maturation of primary oocyte and
completes the I Meiosis Division
– producing 1 secondary oocyte (with
original cytoplasm)
– and 1 polar body (that disintegrates)
– 22 autosomes and 1 X sex chromosome

II Meiosis Division (at ovulation)
– Ovum an & 3rd polar body are formed
– The first polar also divides to form 2
additional polar bodies

Result: 1 ovum+3 polar body
Gametogenesis

Oogenesis
Primary oocyte
Secondary
oocyte+polar body
mature ovum+3 polar
body
Gametogenesis: Spermatogenesis vs
Oogenesis
Ovum


Meiosis occurs in the female in the ovarian
follicles and produces an egg, or ovum. Each
month, one ovum matures with a host of
surrounding supportive cells.
At ovulation the ovum is released from the
ruptured ovarian follicle. High estrogen levels
increase the motility of the uterine tubes so their
cilia are able to capture the ovum and propel it
through the tube toward the uterine cavity. An
ovum cannot move by itself.
Ovum
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Two protective layers surround the ovum.
The inner layer is a thick, acellular layer, the zona
pelluada.
The outer layer, the corona radiata, is composed of
elongated cells.
Ova are considered fertile for approximately 24 hours
after ovulation. If unfertilized by a sperm, the ovum
degenerates and is reabsorbed.
Sperm

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Ejaculation during sexual intercourse normally propels
almost a teaspoon of semen containing as many as 200
million to 500 million sperm into the vagina.
The sperm swim with the flagellar movement of their
tails.
Some sperm can reach the site of fertilization within 5
minutes, but average transit time is 4 to 6 hours.
Sperm remain viable within the woman's reproductive
system for an average of 2 to 3 days. Most sperm are lost
in the vagina, within the cervical mucus, or in the
endometrium, or they enter the tube that contains no
ovum.
As sperm travel through the female reproductive tract,
enzymes are produced to aid in their capacitation.
Capacitation is a physiologic change that removes the
protective coating from the heads of the sperm. Small
perforations then form in the acrosome (a cap on the
sperm) and allow enzymes (e.g., hyaluronidase) to escape.
These enzymes are necessary for the sperm to penetrate
the protective layers of the ovum before fertilization.
Fertilization
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Takes place in the ampulla of uterine tube
When a sperm successfully penetrates the membrane
surrounding the ovum, both sperm and ovum are
enclosed within the membrane, and the membrane
becomes impenetrable to other sperm; this is termed
the zona reaction.
The second meiotic division of the oocyte is then
completed, and the ovum nucleus becomes the female
pronucleus. The head of the sperm enlarges to become
the male pronucleus, and the tail degenerates.
The nuclei fuse and the chromosomes combine,
restoring the diploid number (46).
Conception, the formation of the zygote, is now
complete.
Fertilization
Fertilization
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Mitotic cellular replication, called cleavage, begins as the zygote travels the
length of the uterine tube into the uterus. This voyage takes 3 to 4 days.
Because the fertilized egg divides rapidly with no increase in size,
successively smaller cells, blastomeres, are formed with each division.
A 16-cell morula, a solid ball of cells, is produced within 3 days, and is still
surrounded by the protective zona pellucida. Further development occurs as
the morula floats freely within the uterus.
Fluid passes through the zona pellucida into the intercellular spaces between
the blastomeres, separating them into two parts: the trophoblast (which gives
rise to the placenta) and the embryoblast (which gives rise to the embryo). A
cavity forms within the cell mass as the spaces come together, forming a
structure termed the blastocyst cavity.
When the cavity becomes recognizable, the whole structure of the
developing embryo is known as the blastocyst. The outer layer of cells
surrounding the cavity is the trophoblast
Fertilization
Implantation
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The zona pellucida degenerates, and
the trophoblast attaches itself to the
uterine endometrium, usually in the
anterior or posterior fundal region.
Between 6 and 10 days after
conception, the trophoblast secretes
enzymes that enable it to burrow into
the endometrium until the entire
blastocyst is covered. This is termed
implantation.
Endometrial blood vessels erode, and
some women experience
implantation bleeding (slight
spotting and bleeding during the time
of the first missed menstrual period).
Implantation
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Chorionic villi, or fingerlike projections,
develop out of the trophoblast and extend into
the blood-filled spaces of the endometrium.
These villi are vascular processes that obtain
oxygen and nutrients from the maternal
bloodstream and dispose of carbon dioxide and
waste products into the maternal blood
After implantation, the endometrium is termed
the decidua.
The portion directly under the blastocyst,
where the chorionic villi tap the maternal
blood vessels, is the decidua basalis.
The portion covering the blastocyst is the
decidua capsularis,
and the portion lining the rest of the uterus is
the decidua vera
EMBRIO AND FETUS
EMBRIO AND FETUS
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Pregnancy lasts approximately 10 lunar months (9 calendar
months, 40 weeks, or 280 days). Length of pregnancy is
computed from the first day of the last menstrual period (LMP)
until the day of birth. However, conception occurs approximately
2 weeks after the first day of the LMP. Thus the postconception
age of the fetus is 2 weeks less, for a total of 266 days, or 38
weeks. Postconception age is used in the discussion of fetal
development.
Intrauterine development is divided into three stages:
– preembryonic (from conception until day14. This period
covers cellular replication, blastocyst formation, initial
development of the embryonic membranes, and
establishment of the primary germ layers)
– Embryo (2nd week after fertilization until the end of the 2nd month.
Development of organs and systems)
– Fetus (the 3rd through the 9th months of development)
Early Developmental Stages
Primary Germ Layers
Ectoderm, Mesoderm and Endoderm
During gastrulation, three major cell lineages are being established. They are the Ectoderm (shown in the diagram as blue),
Mesoderm (red) and Endoderm (yellow). Following gastrulation, various cell lineages are derrived from these three primary
cell types. For example, the Ectoderm gives rise to the epidermis and its derrivatives such as nails, hair and teeth. On the
other hand, the Ectoderm also gives rise to the Central Nervous System.
Development of the embrio
Membranes
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At the time of implantation, two fetal membranes that will
surround the developing embryo begin to form. The chorion
develops from the trophoblast and contains the chorionic
villi on its surface. The villi burrow into the decidua basalis
and increase in size and complexity as the vascular
processes develop into the placenta. The chorion becomes
the covering of the fetal side of the placenta. It contains the
major umbilical blood vessels that branch out over the
surface of the placenta. As the embryo grows, the decidua
capsularis stretches. The chorionic villi on this side atrophy
and degenerate, leaving a smooth chorionic membrane.
The inner cell membrane, the amnion, develops from the
interior cells of the blastocyst. The cavity that develops
between this inner cell mass and the outer layer of cells
(trophoblast) is the amniotic cavity. As it grows larger, the
amnion forms on the side opposite to the developing
blastocyst. The developing embryo draws the amnion
around itself to form a fluid-filled sac. The amnion becomes
the covering of the umbilical cord and covers the chorion on
the fetal surface of the placenta. As the embryo grows
larger, the amnion enlarges to accommodate the
embryo/fetus and the surrounding amniotic fluid. The
amnion eventually comes in contact with the chorion
surrounding the fetus.
AMNIOTIC FLUID
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At first the amniotic cavity derives its fluid by diffusion from the maternal blood. The amount of
fluid increases weekly, and 800 to 1200 ml of transparent liquid is normally present at term.
The amniotic fluid volume changes constantly.
–
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Volume
–
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Oligohydramnios - less than 300 ml of amniotic fluid is associated with fetal renal abnormalities
Hydramnios - more than 2 L of amniotic fluid is associated with gastrointestinal and other malformations
Function
–
–
–
–
–
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the fetus swallows fluid
fluid flows into and out of the fetal lungs
the fetus urinates into the fluid, greatly increasing its volume
helps maintain a constant body temperature
a source of oral fluid and as a repository for waste
protect the fetus from trauma by blunting and dispersing outside forces
allows freedom of movement for musculoskeletal development
keeps the embryo from tangling with the membranes
Amniotic fluid contains albumin, urea, uric acid, creatinine, lecithin, sphingomyelin, bilirubin,
fructose, fat, leukocytes, proteins, epithelial cells, enzymes, and lanugo hair.
Study of fetal cells in amniotic fluid through amniocentesis yields much information about the
fetus.
Genetic studies (karyotyping) provide knowledge about the sex and the number and structure of
chromosomes. Other studies, such as the lecithin/sphingomyelin ratio, determine the health or
maturity of the fetus.
Yolk Sac
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At the same time the amniotic cavity and amnion are forming,
another blastocyst cavity forms on the other side of the
developing embryonic disk. This cavity becomes surrounded
by a membrane, forming the yolk sac. The yolk sac aids in
transferring maternal nutrients and oxygen, which have
diffused through the chorion, to the embryo. Blood vessels
form to aid transport. Blood cells and plasma are manufactured
in the yolk sac during the second and third weeks. At the end of
the third week, the primitive heart begins to beat and circulate
the blood through the embryo, connecting stalk, chorion, and
yolk sac.
The folding in of the embryo during the fourth week results in
incorporation of part of the yolk sac into the embryo's body as
the primitive digestive system. Primordial germ cells arise in
the yolk sac and move into the embryo.
The shrinking remains of the yolk sac degenerate. By the fifth
or sixth week, the remnant has separated from the embryo.
Umbilical cord
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By day 14 after conception the embryonic disk, amniotic sac, and
yolk sac are attached to the chorionic villi by the connecting stalk.
During the third week the blood vessels develop to supply the
embryo with maternal nutrients and oxygen. During the fifth week,
after the embryo has curved inward on itself from both ends
(bringing the connecting stalk to the ventral side of the embryo), the
connecting stalk becomes compressed from both sides by the
amnion, forming the narrower umbilical cord. Two arteries carry
blood to the chorionic villi from the embryo, and one vein returns
blood to the embryo.
The cord rapidly increases in length. At term the cord is 2 cm in
diameter and ranges from 30 to 90 cm in length (with an average of
55 cm). It twists spirally on itself and loops around the embryo/fetus.
A true knot is rare, but false knots occur as folds or kinks in the cord
and may jeopardize circulation to the fetus. Connective tissue called
Wharton's jelly prevents compression of the blood vessels and
ensures continued nourishment of the embryo/fetus. Compression
can occur if the cord lies between the fetal head and the pelvis or if it
is twisted around the fetal body. When the cord is wrapped around
the fetal neck, it is termed a nuchal cord.
Because the placenta develops from the chorionic villi, the umbilical
cord is usually located centrally. A peripheral location is less
common and is termed battledore placenta.
The blood vessels are arrayed out from the center to all parts of the
placenta.
Placenta. Structure
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The placenta begins to form at implantation. During
the third week after conception, the trophoblast cells of
the chorionic villi continue to invade the decidua
basalis. As the uterine capillaries are tapped, the
endometrial spiral arteries fill with maternal blood. The
chorionic villi grow into the spaces with two layers of
cells: the outer syncytium and the inner
cytotrophoblast. A third layer develops into anchoring
septa, dividing the projecting decidua into separate
areas called cotyledons. In each of the 15 to 20
cotyledons, the chorionic villi branch out, and a
complex system of fetal blood vessels forms. Each
cotyledon is a functional unit. The whole structure is
the placenta.
The maternal-placental-embryonic circulation is in
place by day 17, when the embryonic heart starts
beating.
By the end of the third week, embryonic blood is
circulating between the embryo and the chorionic villi.
In the intervillous spaces, maternal blood supplies
oxygen and nutrients to the embryonic capillaries in
the villi. Waste products and carbon dioxide diffuse
into the maternal blood.
Functions of the placenta:
1. Transfer gasses
2. Transport nutrients
3. Excretion of wastes
4. Hormone production – temporary endocrine
organ – estrogen and progesterone
5. Formation of a barrier – incomplete,
nonselective – alcohol, steroids, narcotics,
anesthetics, some antibiotics and some
organisms can cross
Hormones of Placenta
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human chorionic gonadotropin (hCG) – detected 8-10 days after conception or
shortly after implantation, basis of pregnancy test, preserves the function of the
ovarian corpus luteum, ensuring a continued supply of estrogen and progesterone
needed to maintain the pregnancy. Miscarriage occurs if the corpus luteum stops
functioning before the placenta is producing sufficient estrogen and progesterone.
The hCG reaches its maximum level at 50 to 70 days, then begins to decrease
human placental lactogen (hPL) or human chorionic somatomammotropin - similar
to a growth hormone and stimulates maternal metabolism to supply needed nutrients
for fetal growth. This hormone increases the resistance to insulin, facilitates glucose
transport across the placental membrane, and stimulates breast development to
prepare for lactation.
placental prolactin - Helps convert mammary glands to active status
Relaxin- Increases flexibility of pubic symphysis, permitting pelvis to expand
during delivery
Progesterone – maintains the endometrium, decreases the contractility of the uterus,
and stimulates development of breast alveoli and maternal metabolism
Estrogens – stimulates uterine growth and uteroplacental blood flow, causes a
proliferation of the breast glandular tissue and stimulates myometrial contractility.
Placental estrogen production increases greatly toward the end of pregnancy.
Extraembryonic Membranes & Placenta Formation
Figure 29–5 (1 of 3)
G. Fetus at 2-3weeks
1/10 of an inch long
nervous system is developing
blood cells are developed
H. Fetus at 4 weeks
May float freely for 48 hours before implanting
Arm buds start to be evident
gets more of a curved appearance
eyes start to develop
implantation of to the uterus and placenta is
taking place
I. The Fetus at 5 weeks
•The nose starts to form
•Placental blood vessels form
•endocardial(muscle) cells begins to
form the
two heart tubes
J. The Fetus at 6 weeks
•1/2 inch long (floating in amniotic fluid)
•leg buds present
•spine is visible
•ears are forming
•at 6 weeks heart muscle starts to beat
•has rapid growth at this stage
•head/mouth/liver/intestines start to take
shape
K. The Fetus at 7 weeks
• 3/4 inches long
• Hand/fingers are formed and moving
•eye lens form
•skull bones are visible and growing
•sexual organs are forming
•brain waves have started
•muscles develop and get stronger
L. Fetus at 8-9 weeks old
Heart Development Ends
The brain can move muscles
Sexual organs are forming
Feet become more defined
Digits are separating on hands/feet
Toe/Finger joints are visible
As you can see the fetus is in its
own sac of amniotic fluid attached to
the mother by an umbilical cord
to the placenta where it gets all it’s
nourishment from. (Above are two
twin boy fetuses in separate sacs)
M. 10 Week Old Fetus
(2 1/2 months old) Now considered a fetus
• 1-2 inches long
•Has a stump for a tail’
• Is now very active
• Facial features developed
• Fingers/ Toes/ Hands/ Feet developed
•Internal Organs are functioning
• Nervous System is responsive: He/She can feel!
N. 11 Weeks old:
Now is 2 1/2 inches long
12 WEEKS(3 months)
•3 inches long
•umbilical
cord intact and
is fully
functional
14 WEEKS (3 1/2 months)
•3- 31/2 inches
•weight is 1 ounce
•muscles are
developing
•sex organs form
•eyelids form
•fingernails and toenails
•spontaneous
movement is observed
15-18 WEEKS
( 4-4 1/2 months)
•Sensory Organs
form at (15)
•(16) is turning
inside of MOM
•(18) 5 1/2 inches
•blinks, grasps,
moves mouth,
hair on head and
body is present
•all systems are
developed
•fetal respiration's
are occurring
•Must be at least
24 weeks to
survive outside of
womb
WEEK 22 (2 1/2 months)
•1/2 pound
•10 inches
long
•sweat glands
•external skin
is turning from
transparent to
opaque
WEEK 26
(6 1/2 Months
•Inhales and
exhales
•cries
•eyes are
completely
formed
•has tongue and
taste buds
•has a 50%
chance of
survival outside
of the womb
with intensive
Medical care
WEEK 30
(7 1/2 months)
(7 1/2 mo.)
•Is premature
if born
•But most do
well if born at
this time
•Girls fair
better than
boys because
their lungs are
more
developed.
FULL TERM (36 -40 weeks)
This is the end of
normal
gestation….
Baby is now able
to live outside of
the mother’s
womb.
Normal pregnancy
The Start of It All
In either case, the process will
inevitably involve a sperm and an egg
Or….for those women who get tired of
waiting for the “right man”
Pregnancy is a normal physiologic
process . . .
. . . not a disease!
Signs of pregnancy
 Presumptive (generally subjective)
 Probable (objective)
 Positive (diagnostic)
Presumptive symptoms of
pregnancy:
Cessation of menses
 Nausea with or without vomiting
 Frequent urination
 Fatigue
 Breast tenderness, fullness, tingling
 Maternal perception of fetal movement
(“Quickening”)

Presumptive signs of pregnancy:
Breast changes – enlargement,
hyperpigmentation, Montgomery’s
tubercles
 Bluish or purplish coloration of the vaginal
mucosa and cervix (Chadwick’s sign)
 Increased skin pigmentation – chloasma,
linea nigra
 Appearance of striae on abdomen and
breasts

Probable signs of pregnancy:
Enlargement of the abdomen
 Changes in the size, shape, and
consistency of the uterus
 Changes in the cervix
 Palpation of Braxton-Hicks contractions
 Outlining the fetus manually
 Endocrine tests of pregnancy

Positive signs of pregnancy:
Identification of the fetal heart beat
separately and distinctly from that of the
mother
 Perception of fetal movements by the
examiner
 Visualization of pregnancy on ultrasound
 Fetal recognition on X-ray

Expected Physical Changes Cardiovascular
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Blood volume increase
Physiological anemia
Vital signs stable
Increased clotting factors
Edema
Cardiovascular Changes During Pregnancy
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Heart Rate:  15% ( 10-20 bpm)
Stroke Volume:  50%
Cardiac Output:  30-50% (6.2±1.0 L/min)
– Nonpregnant is 4.30.9 L/min
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Blood Pressure:  3-5 mmHg systolic and 5-10
mmHg diastolic in the first trimester and
returns to the patient’s prepregnant level by
term
Systemic Vascular Resistance:  21% (1210
dyne·cm·sec-5 versus 1530 dyne·cm·sec-5 )
Colloid Oncotic Pressure:  20% (18.0 ±1.5
mmHg)
– Nonpregnant is 20.8 ±1.0 mmHg
Hematologic Changes During Pregnancy

Blood Volume:  45% ( 1450-1750 ml)
– Protects the mother from devastating hemorrhage at
delivery

Plasma Volume:  45-50% ( 1200-1300 ml)
– Serves to dissipate fetal heat production

Red Cell Mass:  18-30% ( 250-450 ml)
– Necessary to  O2 transport to meet fetal needs

Based on the above, pregnancy normally results
in a “physiologic anemia”
– Hgb: 10-12 g/dL (nonpregnant = 12-15 g/dL)
– Hct: 32-40% (nonpregnant = 35-47%)
Hematologic Changes During Pregnancy—
cont.

WBC: 
– 1st Trimester: 3,000-15,000/mm3
 (mean 9500/ mm3)
– 2nd & 3rd Trimesters: 6,000-16,000/mm3
 (mean 10,500/ mm3)
– Labor: 20,000-30,000/mm3
Expected Physical ChangesRespiratory
 Oxygen consumption increases with decrease
airway resistance
 Deeper respirations and upward pressure on
diaphragm
Respiratory
Changes During Pregnancy
 Respiratory Rate: Unchanged or slight 

Tidal Volume (Vt):  30-40%
– This  occurs at the expense of the expiratory
reserve volume (ERV) which  20%
– Vital capacity (VC) & inspiratory reserve volume
(IRV) remain relatively stable
Respiratory Changes During Pregnancy

pH: slight  to 7.40-7.45
– Remains roughly at nonpregnant level because the 
PaCO2 is compensated for by  renal excretion of
bicarbonate (HCO3)
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Serum HCO3:  (18-31 mEq/L)
Oxygen consumption:  15-29%
PaO2: 104-108 mmHg
PaCO2: 27-32 mmHg
– ~40 mmHg in nonpregnant women
– The above change in PaO2 and PaCO2 is very
important b/c it  the CO2 gradient between the fetus
and mother, therefore, facilitating the transfer of CO2
from the fetus to the mother
Expected Physical Changes Gastrointestinal and Urinary
Systems
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
Nausea, vomiting, constipation, slowed peristalsis
Bladder capacity increases and tone decreases; risk
of UTIs increases
GI Changes
Appetite
 Gastric emptying
 Absorption
 Bowel sounds
 Blood flow to the pelvis
 Morning sickness
 Pyrosis
 Constipation

Gallbladder and Liver
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Gallbladder with decreased tone
Renal Function Changes During Pregnancy
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Kidneys enlarge with a length  of ~1 cm as
measured by intravenous pyelography
Renal Plasma Blood Flow
–  30-50% by the end of the first trimester

GFR
–  30-50% by the end of the first trimester

The  in Renal Plasma Flow and GFR are
responsible for decreases in the following:
– Uric acid (serum) 4.5 mg/dL
– BUN (serum) 12 mg/dL
– Creatinine (serum) 0.5-0.6 mg/dL

Creatinine Clearance 150-200 mL/min
Clotting Factor Changes During Pregnancy
 Fibrin:  40% at term
 Plasma Fibrinogen (Factor I):  50%
 Clotting time: Unchanged
 Coagulation Factors V, VII, VIII, IX, X,
XII all 
 Coagulation Factors XI, XIII both 
slightly
 Prothrombin time: Unchanged or 
slightly
 Platelets: Unchanged
Expected physical changes Integumentary System
 Hyperpigmentation
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
Linea Nigra
Melasma
Skin Changes
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Increased subdermal fat
Hyperpigmentation
Striae
Linea nigra
Chloasma
Angiomas
Pruritis
Palmar erythema
Increased perspiration
Endocrine Changes
Amenorrhea
 Progesterone
 Estrogen
 Ant pituitary suppresses the FSH and LH
causing
to rise
 Post pituitary produces oxytocin

Neurological Changes
Carpal Tunnel Syndrome
 Numbness/Tingling
 Lightheadedness
 Muscle Cramps

Musculoskeletal Changes
Change in posture
 Waddling
 Back Pain

Assessment of Gestational Age

By LMP (last menstrual period) – the mean
length of a normal pregnancy is 280 days
from the first day of the last normal
menstrual period

By physical exam

By ultrasound
Using
the
“Wheel”
 Put the arrow marked


FIRST DAY OF LMP
on the appropriate date
The arrow marked
APPROXIMATE
DATE OF DELIVERY
at the 40-week mark
gives you the EDD
Today’s date gives you
the EGA today
Nagele’s Rule
 Subtract 3 months from that date then add 7
days
 1st day of LNMP (last normal menstrual
period)
Example: LNMP: September 10, 2006
Expected Due Date (EDD): June 17, 2007
Uterine
Sizing
 6 weeks – globular with softening of the
isthmus, size of a tangerine

8 weeks – globular, size of a baseball
10 weeks – globular with irregularity around
one cornua (Piskacek’s sign), size of a
softball
 12 weeks – globular, size of a grapefruit

Expected Physical Changes Reproductive System
Uterine enlargement
 12 weeks – At Symphysis
 16 weeks – Midway between symphysis and
umbilicus
 20 weeks – At the umbilicus
 36 weeks - Near xyphoid process

Uterine Sizing
Accuracy of Dating by Ultrasound
Gestational
Age weeks)
Ultrasound
Measurements
Range of
Accuracy
<8
Sac size
+ 10 days
8-12
CRL
+ 7 days
12-15
CRL, BPD
+ 14 days
15-20
BPD, HC, FL, AC
+ 10 days
20-28
BPD, HC, FL, AC
+ 2 weeks
> 28
BPD, HC, FL, AC
+ 3 weeks
The Trimesters

The “trimesters” are three periods of 14
weeks each
1st trimester = through completion of 14
weeks
 2nd trimester = through completion of 28
weeks
 3rd trimester = 29th through 42nd weeks

Gravida and Para

Gravida means a woman who has been, or
currently is, pregnant

Para means a woman who has given birth

Nulligravida – never been pregnant
Primigravida – pregnant for the first time
Primipara – has delivered once
Multipara – has delivered more than once



GTPAL
G – GRAVIDA (how many pregnancies)
 T – TERM (how many term deliveries)
 P – PRETERM (how many preterm
deliveries)
 A – ABORTIONS (how many abortions,
spontaneous or induced)
 L – LIVING – how many children
currently
living

Term, Preterm, Abortion
TERM means delivery occurring in weeks
38-42
 PRETERM means delivery occurring in
weeks 20-37
 ABORTION means delivery occurring
before 20 weeks
 POSTTERM means delivery occurring
after week 42

Psychological Adaptation and
Developmental Tasks of Pregnancy

1st Trimester
– Accepting reality of pregnancy

2nd Trimester
– Resolving feelings about her own mother;
defining herself as a mother

3rd Trimester
– Active preparation for childbirth and baby
Review of Systems – 1st
Trimester






Nausea
Vomiting
Headaches
Dizziness
Cramping
Urinary frequency




Pain with urination
Changes in discharge
(amount, color, odor)
Pruritis
Bleeding
Review of System – 2nd
Trimester




Gums bleeding
Nose bleeding
Constipation
Fetal movement





Cramping
Bleeding
Dysuria
Abnormal discharge
pruritis
Review of Systems – 3rd Trimester





Indigestion
Swelling
Leg cramps
Fetal movement
Difficulty sleeping






Contractions
Bleeding
Calf pain
Headaches
Epigastric pain
Visual changes
History - Menstrual
 Menarche
 Interval
 Length
 Recent
birth
control or
lactation
 LMP
– Sure of date?
– Normal in length
& flow
 Other helpful tidbits
– Date of
conception
– ER sonogram
Obstetric History
Dates of all pregnancies (include previous
miscarriage or termination)
 GA
 Gender, weight
 Length of labor
 Coping techniques
 Route of delivery

Gynecologic History
Last Pap
 Abnormal pap
 Gyn surgery or problems (e.g. infertility)
 Family planning methods
 Sexually transmitted infections

Medical/Surgical History
Serious illnesses
 Hospitalizations
 Surgery
 Drug allergies or unusual reactions
 Meds since LMP

Family History

Maternal
–
–
–
–
Diabetes
Pre-eclampsia
Preterm delivery
Cancers (breast,
ovarian, colon)
– Depression, bipolarity
– Twins
– Anesthesia reactions

Maternal or Paternal
–
–
–
–
Birth defects
Mental retardation
Bleeding disorders
Chromosomal
abnormalities (e.g.
Down Syndrome)
Vital Signs




Temperature
Blood pressure
Respirations
Radial pulse





Elevated BP suggests the presence of preeclampsia.
Elevated BP may be defined as a persistently
greater than 140 systolic or 90 diastolic.
Usually, if one is elevated, both are elevated.
Elevated temperature suggests the possible
presence of infection.
Many pregnant women normally have oral
temperatures of as much as 99+. These mild
elevations can also be an early sign of infection.
While a pregnant pulse of up to 100 BPM or
greater may be normal, rapid pulse may also
indicate hypovolemia.
Additional Measurements
Height
 Weight
 BMI (Body mass index )

–
–
–
–
–
BMI Categories:
Underweight = <18.5
Normal weight = 18.5-24.9
Overweight = 25-29.9
Obesity = BMI of 30 or greater
The First Prenatal Visit: History
Past medical history
 Family medical history
 Gynecologic history
 Past OB history
 Exposures to infections, teratogens,
genetic problems
 Social history
 Nutritional status

The First Prenatal Visit: Exam








Fundoscopic exam
Teeth
Thyroid
Breasts
Lungs
Heart
Abdomen
Extremities


Skin
Lymph nodes
The First Prenatal Visit: Pelvic Exam

Vulva
Vagina
Cervix
Uterine size
Adnexae
Rectum

Labs:





– Pap
– GC & chlamydia

Clinical pelvimetry:
–
–
–
–
–
Diagonal conjugate
Ischial spines
Sacrum
Subpubic arch
Gynecoid pelvic
type?
Bones and Joints of the Pelvis
The Diagonal Conjugate


The obstetric conjugate
extends from the middle of
the sacral promontory to the
posterior superior margin of
the pubic symphysis. This is
the most important diameter
of the pelvic inlet.
The diagonal conjugate
extends from the subpubic
angle to the middle of the
sacral promontory and can be
measured clinically to
estimate the obstetric
conjugate.
The Ischial Spines

The transverse
diameter, between
the ischial spines, is a
measurement of the
dimensions of the
pelvic cavity
The Pelvic Outlet

Subpubic arch

Bituberous
(transverse) diameter

Inferior pubic rami
The
First
Prenatal
Visit:
Labs
 ABO blood type
D (Rh) type
 Antibody screen
 CBC
 Rubella
 VDRL or RPR
 HBsAg
 HIV (optional)
 Hemoglobin electrophoresis (as appropriate)

The First Prenatal Visit: Counseling






What to expect
during the course of
prenatal care
Risk factors
encountered
Nutrition
Exercise
Work
Sexual activity






Travel, seat belts
Smoking cessation
Avoidance of drugs
and alcohol
Warning signs
Where to go or call in
case of problems
Prenatal vitamins
The Return Prenatal Visit

REVIEW THE CHART!
–
–
–
–
–
Calculate the EGA
Check the labs
Review weight gain
Review blood pressure
Review results of UA
Leopold's Maneuvers - are used to determine
the orientation of the fetus through abdominal

palpation.
1. Using two
hands and
compressing the
maternal
abdomen, a
sense of fetal
direction is
obtained
(vertical or
transverse).

.
2. The sides of the uterus are palpated to
determine the position of the fetal back and small
parts.
3. The presenting part (head or butt) is palpated
above the symphysis and degree of engagement
determined
4. The fetal occipital prominence is
determined.
Measuring Fundal Height
Auscultating Fetal Heart Tones
The Routine OB Visit Schedule

Every 4 weeks until 28 weeks

Every 2 weeks from 28 until 36 weeks

Every week from 36 weeks until delivery

Six weeks postpartum
Other Routine OB Labs

15-20 weeks

Quad Screen

24-28 weeks


Diabetes Screen
Rhogam workup &
injection

Group B strep culture

35-37 weeks
Pregnancy is a normal physiologic
process, not a disease . . .
 however,
pregnancy tends to be
UNCOMFORTABLE.
Your challenge is to differentiate
common discomforts of pregnancy
from pathology!
Nausea with or without Vomiting
Starts at 4-6 weeks, peaks at 8-12 weeks,
resolves by 14-16 weeks
 Causes: unknown; may be rapidly
increasing and high levels of estrogen,
hCG, thyroxine; may have a psychological
component


Rule out: hyperemesis gravidarum
Nausea and vomiting in early
pregnancy
 If
a woman requests or would like to
consider treatment, the following
interventions appear to be effective
in reducing symptoms:
non-pharmacological
– ginger
– P6 acupressure

pharmacological
– antihistamines.
A
Ptyalism

Excessive salivation
accompanied by
nausea and inability
to swallow saliva

Cause: unknown;
may be related to
increased acidity in
the mouth
Fatigue

Causes: unknown;
may be related to
gradual increase in
BMR

Rule out: anemia,
thyroid disease
Backache
Women should be informed
that exercising in water,
massage therapy might
help to ease backache
during pregnancy.
A
Upper Backache

Cause: increase in size and weight of the
breasts

Relief: well-fitting, supportive bra
Low Backache

Cause: weight of the
enlarging uterus
causing exaggerated
lumbar lordosis

Rule out:
pyelonephritis
(CVAT)
Leukorrhea

Definition: a profuse, thin or thick white
vaginal discharge consisting of white
blood cells, vaginal epithelial cells, and
bacilli; acidic due to conversion of an
increased amount of glycogen in vaginal
epithelial cells into lactic acid by
Doderlein’s bacilli

Rule out: vaginitis, STI, ruptured
membranes
Urinary Frequency



1st trimester: increased
weight, softening of the
isthmus, anteflexion of
the uterus
3rd trimester: pressure of
the presenting part
Rule out: UTI
Heartburn




Relaxation of the cardiac
sphincter due to progesterone
Decreased GI motility due to
smooth muscle relaxation
(progesterone)
Lack of functional room for the
stomach because of its
displacement and compression
by the enlarging uterus
Rule out: GI disease
Heartburn
 Women
who present with symptoms
of heartburn in pregnancy should
be offered information regarding
lifestyle and diet modification. GPP
 Antacids may be offered to women
whose heartburn remains
troublesome
A
Constipation



Decreased peristalsis due to
relaxation of the smooth
muscle of the large bowel
under the influence of
progesterone
Displacement of the bowel
by the enlarging uterus
Administration of iron
supplements
Constipation
Women who present with
constipation in pregnancy
should be offered information
regarding diet modification,
such as bran or wheat fibre
supplementation.
A
Hemorrhoids



Relaxation of vein walls and
smooth muscle of large
bowel under influence of
progesterone
Enlarging uterus causes
increased pressure,
impeding circulation and
causing congestion in pelvic
veins
Constipation
Hemorrhoids
Women
should be offered
information concerning diet
modification.
If clinical symptoms remain
troublesome, standard
hemorrhoids creams should be
considered.
GPP
Leg Cramps

Cause: unknown. ? inadequate calcium, ? Imbalance in
calcium-phosphorus ratio

Relief: straighten the leg and dorsiflex the foot:
Dependent Edema

Cause: impaired
venous circulation
and increased venous
pressure in the lower
extremities

Rule out: preeclampsia
Varicosities




Impaired venous circulation and increased
venous pressure in lower extremities
Relaxation of vein walls and surrounding smooth
muscle under the influence of progesterone
Increased blood volume
Familial predisposition
Varicose veins
Varicose
veins are a common
symptom of pregnancy that will
not cause harm
and
Compression stockings can
improve the symptoms but will not
prevent varicose veins from
emerging.
A
Vaginal discharge
Women should be informed
that an increase in vaginal
discharge is a common
physiological change that
occurs during pregnancy.
GPP
Vaginal discharge
If vaginal discharge is associated
with itching, soreness, offensive
smell or pain on passing urine
there may be an infective cause
and investigation should be
considered.
GPP
Vaginal discharge
A 1-week course of a topical
imidazole is an effective
treatment and should be
considered for vaginal
candidiasis infections in
pregnant women.
A
Vaginal discharge
The effectiveness and safety
of oral treatments for
vaginal candidiasis in
pregnancy is uncertain and
these should not be
offered.
GPP
Insomnia




Discomfort of the enlarged uterus
Any of the common discomforts of pregnancy
Fetal activity
Psychological causes
Round Ligament Pain
Round ligaments attach on


either side of the uterus
just below and in front of
insertion of fallopian
tubes, cross the broad
ligament in a fold of
peritoneum, pass through
the inguinal canal, insert in
the anterior portion of the
labia majora
When stretched, they hurt!
Hyperventilation
and Shortness of Breath

Causes:
– Increase in the BMR
– Pressure of the uterus on
the diaphragm
– Changes in the oxygencarbon dioxide balance
– Exertion of carrying extra
weight

Rule out: asthma,
pneumonia, TB, anxiety
Supine Hypotensive Syndrome
Screening for
hematological
conditions
Anemia
Pregnant
women should be
offered screening for anaemia.
Screening should take place early
in pregnancy (at the first
appointment) and at 28 weeks.
This allows enough time for
treatment if anaemia is detected.
B
Anemia
Hemoglobin levels outside the
normal range for pregnancy
(that is, 11 g/dl at first contact
and 10.5 g/dl at 28 weeks)
should be investigated and
iron supplementation considered
if indicated.
A
Blood grouping and
red cell alloantibodies
Women should be offered
testing for blood group
and RhD status in early
pregnancy.
B
Blood grouping and
red cell alloantibodies
If a pregnant woman is RhDnegative, offer partner testing
to determine whether the
administration of anti-D
prophylaxis is necessary.
B
Blood grouping and
red cell alloantibodies
It is recommended that
routine antenatal anti-D
prophylaxis is offered to
all non-sensitized
pregnant women who
are
NICE 2002
Blood grouping and
red cell alloantibodies
Women should be screened for
atypical red cell
alloantibodies in early
pregnancy and again at 28
weeks regardless of their RhD
D
status.
Blood grouping and
red cell alloantibodies
Pregnant women with clinically
significant atypical red cell
alloantibodies should be offered
referral to a specialist centre for
further investigation and advice
on subsequent antenatal
management.
GPP