Download Physiological changes

Normal Pregnancy, Anatomical &
Physiological changes
Dr. Dina Nawfal
Department of Obstetrics & Gynecology
College of Medicine
University of Mosul
Normal Pregnancy, Anatomical & Physiological
changes
 During early pregnancy the developing fetus, corpus
luteum and placenta produce and release increasing
quantities of hormones, growth factors into the maternal
circulation
 most pregnant women report symptoms of pregnancy by
the end of the sixth week
 it is assumed that most of the physiological
adaptation are completed during the first trimester.
Volume homeostasis
 Blood volume expands during pregnancy to allow adequate
perfusion to the vital maternal organs , placenta and fetus
The increase mainly involve the extracellular fluid volume
specially plasma and begun at 6-8wk, plateau at 32-34wks.
The total body water increase from 6.5 to 8.5L by the end of
pregnancy
changes in osmoregulation of renin-angiotensin system result
in active sodium reabsorption in renal tubules and water
retension
the plasma osmolality decrease by about 10mOsmol/kg
 thirst threshold decreased
 Plasma oncotic presure is mainly determined by albumin
concentration this decrease by about 20% leads to
peripheral edema
Consequences of fluid retention:
 decrease hemoglobin concentration
 reduce hematocrite
 reduce albumin concentration
 increase stroke volume
 increase ranal blood flow
Hematology
hemoglobin level:
 Hemoglobin concentration fall from 13.3 to 10.9 g/dl
 the transfer of iron stores to the fetus contribute to the
development of physiological anemia
iron level:
 iron requirements is increased and hence its absorption
from the gut is increased as a result
 pregnancy without iron supplementation lead to
depletion of iron stores and iron deficiency anemia.
folic acid:
 renal clearance of folic acid increased
 plasma folate concentration fall but red cell folate do not
decrease
Platelet count
 platelet count usually remain stable throughout pregnancy
Although it may be lower than pre pregnancy state due to
increased aggregtion
WBC count
mainly the polymorph nuclear cells will increase during
pregnancy from 3rd weeks of gestation and more
pronounced postpartum.
Haemostasis and coagulation
 Pregnancy is a hypercoagulable state and return to normal
after 4 weeks postpartum
At term the placental bed blood flow is 500ml/min
Almost all clotting factors including factors Vll,Vlll lX,X,
Xll and fibrinogen are increased.
 antithrombin lll remain unchanged
 protein S activity decreases
 activated protein C resistance increase
Respiratory system
Anatomical changes
 The neck , oropharyngeal tissues , breasts and chest
wall are affected by weight gain during pregnancy and
may lead to difficult intubation during general
anasthesia
 nasal congestion
 As pregnancy progresses the diaphragm is elevated
4cm by the enlarging uterus
 Increase pulmonary blood flow
Physiological changes
 the tidal volume increase by 40%
 Increase minute ventilation by 40% ( amount of air move
in and out of lungs in 1minute )
 forced expiratory volume in one second (FEV1) is not
affected
Blood gas changes
 Decrease pco2 .
 Increase po2.
 Increase production 2,3 DPG within the maternal RBCs
to facilitated oxygen delivery to the fetus .
Cardiovascular system
 palpitation are common (sinus tachycardia)
 COP increase by 30-50%
 heart rate increase by about 10-15 beats higher than the
pre pregnancy state
 stroke volume also increase due to changes in plasma
volume
 during early pregnancy blood pressure will decrease by 1015 mmHg diastolic & 5-10mmHg systolic, later on the diastolic
blood pressure will increase to a level at least equivalent to pre
pregnancy state.
 Loud first heart sound and sometimes split
while third heart sound is audible at 20 weeks of gestation
 an ejection systolic murmur is common 96% of pregnant women
 peripheral vascular resistance decrease by 35%
Gastrointestinal tract:
 increase the chance of reflux esophagitis.
 progesterone delay stomach and bowel motility leading
to constipation , hemorrhoid , and increase the risk of
aspiration of the gastric content during general anesthesia
Liver
Increase hepatic blood flow .
 liver function unchanged.
 Increase protein production specially albumin.
 Serum ALT and AST are slightly reduced.
 Serum alkaline phosphatase increase due to
placental production.
The kidney and urinary tract
Anatomical changes
 Kidney increase in size with 1-2cm .
 there is dilatation of pelvic calyces systems under
the influence of progesterone and return to normal
by 6 weeks postpartum.
 Increase Renal blood flow by 80% in the 2nd trimester
Physiological changes
Increase glomerular filteration rate by 50% after
conception.
 creatinine clearance increased by 25% .
plasma renin and angeotensin 2 activity are increased.
 plasma urea , creatinine , uric acid are decreased
due to increase renal excretion .
Sodium and potassium metabolism remain unchanged.
Renal excretion of calcium ,proteins and folic acid
increase.
 Glycosuria are common
Reproductive organs
Uterus
 hyperplasia and hypertrophy of the myometrial cells
increasing the weight of the uterus from 70 gm prior
to pregnancy to 1000gm by term
 Normally the uterus is anteverted but become more axial
and vertical when enlarged and rotate in its long axis, usually
to the right
the intercellular gap junctions develop with increasing
gestation.
Cervix
 Early in pregnancy the cervix become soft and
its color change to purple due to increase vascularity
The cervix become soft in consistency (Hegar sign )
 Cervical mucosal cells produce large amounts of
thick mucus that obstructs the cervical canal soon after
conception it has abundance of leucocytes and acts as
antibacterial and mechanical barrier
Vagina
 Increased vascularity of the vagina resulting
in the violet color characteristic of pregnancy .
 Estrogen cause thickening of the vaginal
epithelium with increase rate of desquamation ,
glycogen storage and lactic acid production ,
transudation of the fluid resulting in increase
in the acidic vaginal discharge .
Breast
 Tenseness and pain in the breast are the symptoms of
pregnancy
The breast progressively increase in size
The primary areola become larger and darkly pigmented
Secondary pigmented areola develops around the primary
areola
 Montgomery's tubercles appears
Estrogen causing increase glandular ducts
formation while Progesterone and human placental
lactogen increase glandular alveoli proliferation
Skin Changes
 Cloasma or the mask of pregnancy is hyper pigmentation
with irregular areas on the cheeks and nose , it may be due
to melanocyte stimulating hormone produced by the
placenta and estrogen and progesterone which may also
have a melanocyte stimulating effect.
Striae gravidarum : Reddish to purple depressed lines
develop in the skin of the abdomen , breasts and
thighs , after pregnancy becomes silvery white due to
stretching of the skin and breaking of the underlying tissue.
 Linea nigra: The midline of the abdominal skin
that extending from the umbilicus to the symphysis
pubis becomes pigmented , brownish-black color
 Sebaceous glands activity increase .
•Pruritis and hirsuitism are common .
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