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AMERICAN SOCIETY FOR REPRODUCTIVE MEDICINE
Formerly The American Fertility Society
OVULATION
DETECTION
A Guide for Patients
PATIENT INFORMATION SERIES
Published by the American Society for Reproductive Medicine under the direction of
the Patient Education Committee, the Publications Committee, and the Nurses
Professional Group. No portion herein may be reproduced in any form without written permission. This booklet is in no way intended to replace, dictate, or fully define
evaluation and treatment by a qualified specialist. It is intended solely as an aid for
patients seeking general information on infertility evaluation, treatment, research,
and related topics.
Copyright 1995 by American Society for Reproductive Medicine.
AM E RI CAN S OCIE TY F OR RE PR OD UCT IVE M ED IC IN E
Formerly The American Fertility Society
OVULATION DETECTION
AGuide for Patients
A glossary of italicized words is located at the end of this booklet.
INTRODUCTION
Ovulation, the release of an egg from its follicle in one of the two ovaries,
is one of the most important factors in conceiving a child. In order for traditional conception to occur, the man must ejaculate his semen, the fluid
containing the sperm, into the woman’s vagina near the time of ovulation.
Once ovulated, the egg is picked up by one of the fallopian tubes and begins
traveling toward the uterus (Figure 1). The man’s sperm must be capable of
swimming through the vagina and cervical mucus, up the cervical canal into
the uterus, and up into the fallopian tube, where it must attach to and
penetrate the egg in order to fertilize it. The fertilized egg continues
traveling to the uterus and implants in the endometrium, where it grows and
matures. If all goes well, a child is born approximately nine months later.
Because a variety of problems can prevent or disrupt ovulation and result
in infertility, it is often necessary to determine whether or not a woman is
ovulating. There are several ways to detect ovulation, including the basal body
temperature (BBT) chart, urine test kits to measure luteinizing hormone
(LH) levels, vaginal ultrasound, an endometrial biopsy, and blood tests to
measure hormone levels. This booklet describes how ovulation occurs and
methods of detecting ovulation.
The Menstrual Cycle and Ovulation
Ovulation is triggered by the LH surge and occurs approximately 36
hours after the start of this surge. If the egg is fertilized and implants in the
endometrium, a pregnancy is established. If a pregnancy is not established,
the endometrial lining that develops in preparation for pregnancy is shed as
the menstrual flow.
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Uterus
Ovary
Fallopian
Tube
Fertilization
Usually
Occurs Here
Cervix
Endometrium
Cervical
Mucus
Egg
Released
(ovulated)
Sperm
Vagina
Figure 1. The female reproductive tract. Solid arrows indicate path sperm
must travel to reach the egg. Dotted arrow indicates path of egg. The
fertilized egg continues traveling through the fallopian tube to the uterus.
Unlike men who continuously produce new sperm throughout their lives,
a woman is born with all of the eggs that she will ever have. These eggs
remain in an immature state within the ovary until they either undergo
ovulation or atresia (degeneration). Ovulation is a complex sequence of events
involving hormones from the hypothalamus, pituitary, and thyroid glands,
including gonadotropin releasing hormone (GnRH), follicle stimulating
hormone (FSH), luteinizing hormone (LH), prolactin, and thyroid hormone.
The hormones released by the egg’s follicle in the ovary cause the
endometrium to develop in anticipation of implantation. The coordination of
this system is one of the most remarkable events in the body, resulting in the
release of a mature egg at the exact time the cervical mucus is most
receptive to sperm. Fertilization usually occurs in the fallopian tube 12 to 24
hours after ovulation. After this period of time, the egg loses its ability to be
fertilized and begins to degenerate. If fertilized, the resulting embryo reaches
the uterus about three to four days later and begins to implant in the
endometrium.
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The menstrual cycle is divided into three phases: the follicular phase,
mid-cycle, and the luteal phase. The follicular phase lasts 10 to 14 days,
beginning with the onset of menstruation and lasting until the onset of the
LH surge. During the follicular phase, the hormone FSH triggers the
development of many follicles and encourages the egg in the dominant
follicle to mature. The dominant follicle increases in size and secretes
estrogen into the bloodstream. The increasing levels of estrogen cause the
hypothalamus and pituitary to decrease the production of FSH, insuring the
development of a single egg.
As the egg matures during the mid-cycle, estrogen levels rise, triggering
the pituitary gland to release a large amount of LH (the LH surge), which
stimulates the release (ovulation) of the egg from its follicle in the ovary.
The LH surge usually occurs 34 to 36 hours prior to ovulation. It can be
measured in either the blood or the urine.
The luteal phase, which generally lasts about 14 days, begins after
ovulation, when the empty follicle collapses and becomes known as the
corpus luteum. The corpus luteum secretes large amounts of progesterone,
the hormone responsible for the rise in basal body temperature characteristic
of the luteal phase. Progesterone also induces specific changes in the
endometrium that make it receptive for embryo implantation. The highest
levels of progesterone occur about one week after ovulation and then decline
if a pregnancy does not result. Declining progesterone levels allow breakdown of the endometrium, which results in menstruation. A b n o r m a l
progesterone secretion may be caused by poor follicular development, inadequate LH levels during the mid-cycle surge, or inadequate LH after ovulation.
SIGNS OF OVULATION
Cycle Length
In most women aged 15 to 44, the average menstrual cycle length is 28
days. However, normal menstrual cycles may range from 21 to 35 days. The
menstrual cycle starts on the first day of menstrual flow. Ovulation usually
occurs between the 13th and 15th day of a 28-day cycle. Keeping track of
menstrual cycle length can help determine the approximate time of ovulation.
Abdominal Pain
Mittelschmerz refers to a pain on one side of the abdomen near the time of
ovulation. Mittelschmerz discomfort may begin prior to actual ovulation and
is generally caused by nerve fibers that stretch as the follicle matures. Pain
experienced after ovulation is usually due to irritation of the body lining
(peritoneum) by the small amount of fluid or blood that leaks into the pelvis
after ovulation. This pain may last for one to two days.
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Cervical Mucus Test (Billings Method)
Another indication of impending ovulation is an increase in cervical mucus
discharged from the vagina and sometimes visible to the woman (Figure 2).
This is due to the increasing estrogen secreted by the growing ovarian
follicle. Early in the cycle, the cervix is closed and there is no mucus. When
mucus production begins, the early mucus is thick, cloudy, and sticky. As the
cycle progresses, the mucus becomes abundant, slippery, clear, and elastic;
conditions favorable to sperm passage. These changes begin about two or
three days before ovulation. After ovulation, the mucus becomes thick again.
a. Early cycle—
the cervical
mucus is sticky
and does not
stretch.
b. Nearing
ovulation—the
cervical mucus
extends a little
before breaking.
c. Just before
ovulation—the
cervical mucus is
very thin, watery,
and stretchable.
d. After
ovulation—the
cervical mucus
becomes thick
again.
Figure 2. The cervical mucus test can provide information about ovulation.
DETECTING OVULATION
Basal Body Temperature (BBT) Chart
The basal body temperature chart helps to monitor the duration of the
different phases of the menstrual cycle and can help determine if and when
ovulation has occurred. During the follicular phase, the woman’s body
temperature is relatively low. When progesterone production begins at
ovulation, it produces a temperature rise with a minimum increase of 0.5
degrees Fahrenheit (Figure 3). An increased body temperature for several
days indicates ovulation has occurred. BBT charts cannot predict when
ovulation is going to occur; they only confirm that ovulation has occurred
after the fact. The following are general instructions for keeping a basal
body temperature chart:
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1. The chart starts on the first day of menstrual flow. Record the date and
place an “x” on the chart for each day of menstrual bleeding.
2. After your period is over, or on about the fifth day of bleeding, begin
taking your temperature every morning before getting out of bed and before
eating, drinking, or smoking. Record your temperature on the chart every
day, noting any unusual circumstances such as insomnia, illness, or alcohol
consumption. Also note on the chart each time you have sexual intercourse
or have a test for infertility. When your next period begins, start a new chart.
Figure 3. The basal body temperature (BBT) chart.
Blood Tests
Elevated progesterone levels in the blood are usually associated with
ovulation. A blood test to measure progesterone can be performed about one
week before the anticipated onset of the next menstrual period. The LH
surge occurs just before ovulation. LH levels in the blood or urine can be
measured to predict when the follicle is mature and ready for ovulation.
Estrogen is secreted by the growing follicle and rises rapidly prior to ovulation. If ovulation is being induced with fertility drugs, frequent estrogen
level measurements may be needed to determine follicular growth.
Common hormonal problems such as thyroid gland disorders or excessive
secretion of the hormone prolactin can cause ovulatory disturbances. Levels
of these hormones can also be measured by blood tests. In women with
excess hair growth or acne, the physician may suggest measuring the male
hormones (androgens), since increases in these hormones are associated
with adrenal gland and ovarian disorders which can also prevent ovulation.
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Ultrasound
Follicular growth can be measured with ultrasound, a technique which
uses soundwaves to produce an image on a monitor screen. This is a painless
procedure that can be done using either a vaginal probe or an abdominal
scanning device. Prior to ovulation, the follicle is thin-walled and filled with
fluid. As the egg inside the follicle develops, the follicle increases in size.
Ovulation generally occurs when the follicle measures about 1.8 to 2.5
centimeters. Ultrasound is especially useful for timing intercourse or
insemination. In women taking fertility drugs, ultrasound may be performed
on several different days during the menstrual cycle so that each follicle can
be carefully measured and monitored.
Ovulation Prediction Kits
Several ovulation prediction tests are available at drug stores. These kits
use paper dip sticks that show changes in the level of LH in the urine. Once
the LH surge has occurred, ovulation usually takes place within 12 to 44
hours. Urine testing usually begins two days prior to the expected day of
ovulation. For women with 28-day cycles, ovulation usually occurs on days
13 to 15. For women with irregular menstrual cycles, urine testing should be
timed according to the earliest and latest possible dates of ovulation. If the
cycle ranges between 27 and 34 days, ovulation usually occurs between days
13 and 20. Therefore, testing should begin on day 11 and continue until
ovulation is indicated or through day 20. There is an 80 percent chance of
detecting ovulation with five days of testing and a 95 percent chance with
ten days of testing. Once ovulation is documented, it is no longer necessary
to continue testing. Occasionally, ovulation may not occur in a particular
cycle. If ovulation is not detected in two or more consecutive cycles, an
ovulatory problem may be present.
The following are general guidelines for ovulation prediction tests that are
based on detecting LH in the urine:
1. The manufacturer’s instructions should be followed precisely.
2. Urine that is very dilute (light) may not have an adequate concentration of
LH for detection. Therefore, women should avoid food and liquids for two
to four hours before obtaining urine for testing so as to have an adequately
concentrated (dark) urine sample.
3. False positive results in urinary LH detection may occur if the woman is
currently pregnant, has recently been pregnant, or is close to menopause.
Fertility medications such as human menopausal gonadotropin (hMG),
human chorionic gonadotropin (hCG), or clomiphene citrate may also cause
inaccurate results. Women taking any of these drugs should consult their
physician before using a urinary ovulation prediction test and ask the
manufacturer about the medication’s effect on the test kit.
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Endometrial Biopsy
Progesterone helps prepare the endometrium (lining of the uterus) to
receive an embryo. An endometrial biopsy can determine if a woman has
ovulated and if the endometrium has been adequately stimulated with
progesterone. During this office procedure, a small amount of endometrial
tissue from inside the uterine cavity is removed and examined under a
microscope. This test is performed just before menstruation is expected to
begin. In order to interpret the endometrial biopsy, the physician will need to
know the day that menstruation begins after the biopsy. Maintaining a BBT
chart and/or using an ovulation prediction test kit is generally helpful in
determining the best day to perform an endometrial biopsy and also in
interpreting the result.
If the degree of progesterone-induced changes in the endometrium is less
than what is expected, a luteal phase defect may be diagnosed. Asecond biopsy
may be needed to confirm this problem. Medication may be recommended
to help correct the situation. Progesterone given either orally, vaginally, or
by injection after ovulation may help to correct a luteal phase defect by
exerting a direct effect on the endometrium. Clomiphene citrate, an
ovulation-inducing medication, may act indirectly on the endometrium by
improving ovulation. It is not known which treatment is best for luteal phase
defect.
IRREGULAR OVULATION
Abnormal ovulation may appear in several ways. Menstrual cycles that
are shorter than 21 days or longer than 35 days are often associated with
anovulation. Lack of a menstrual period for three months or more is called
oligomenorrhea. The complete absence of menstrual periods is referred to as
amenorrhea.
Many hormonal systems work together to produce regular menstrual
periods, and the hormones that make up these systems are often evaluated to
determine the cause of ovulatory disorders. Therefore, in order to prescribe
the appropriate therapy, physicians may require additional tests to determine
why ovulation is not taking place.
Common conditions that may cause irregular ovulation or anovulation
include disorders of the hypothalamus. Hypothalamic disorders are usually
caused by subtle changes in the signal sent from the hypothalamus to the
pituitary gland. This may result in changes in the secretion of FSH and LH
and may cause ovulatory disturbances. Acute stress as well as rapid weight
loss or weight gain can alter the function of the hypothalamus and pituitary
glands and cause anovulation. An elevation of the pituitary hormone
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prolactin may also lead to absence of menstrual periods and anovulation.
Disturbances involving the thyroid gland can affect ovulation. Although less
common, disorders of the adrenal gland may also be associated with
anovulation. Blood tests are usually needed to confirm the diagnosis of these
disorders.
Polycystic ovary syndrome (PCOS), a condition which is frequently
associated with weight gain, excess hair growth on the face and body, and
irregular menstrual periods, can cause irregular ovulation or anovulation.
Women with PCOS frequently have an increased LH level relative to the
FSH level, which can be detected by a blood test. Increased androgens are
also frequently present. In most cases, medical therapy with fertility drugs is
successful in restoring ovulation. A thorough evaluation, including hormonal
studies and appropriate medical therapy, may be required if these disorders
are suspected. For more information on PCOS, consult the ASRM patient
information booklet entitled Hirsutism and Polycystic Ovarian Syndrome.
DRUGS USED TO REGULATE OVULATION
Clomiphene citrate, the most commonly prescribed ovulation drug, is an
oral medication often used to regulate ovulation or to induce ovulation in
women who are not ovulating or do not have normal menstrual cycles.
Clomiphene citrate is also used to time ovulation for patients who plan to
undergo insemination.
Human menopausal gonadotropins (hMG) are injectable medications that
stimulate multiple follicle development. Physicians may prescribe these
medications for patients who do not respond well to oral therapy such as
clomiphene citrate.
Gonadotropin releasing hormone (GnRH), a hormone secreted by the
hypothalamus which prompts the pituitary gland to release FSH and LH, is
released from the hypothalamus in small amounts approximately every hour
or so. Synthetic GnRH can be administered by a pump to stimulate the
pituitary to secrete LH and FSH. This medication is only useful for women
who are anovulatory due to abnormalities in FSH and LH release.
GnRH analogs may be used as adjunctive therapy to enhance induction of
ovulation with other drugs. These analogs are prescribed to women whose
hormonal patterns interfere with normal follicular development or with the
administration of hMG. For a complete listing of ovulation drugs and more
information on regulating ovulation, consult the ASRM patient information
booklet entitled Ovulation Drugs.
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SUMMARY
Although determining if and when ovulation is occurring may seem
frustrating and time consuming, it is often an essential step toward achieving
pregnancy. It is important that women work with their physicians to decide
which method of ovulation detection is best for them. If these tests indicate
that the woman is not ovulating, has irregular cycles, or has a luteal phase
defect, several treatments are available to correct the problem and increase
the chances of a successful pregnancy.
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GLOSSARY
Adrenal glands. Glands located above each kidney that secrete hormones
(cortisol, adrenaline, and other hormones) that help the body withstand stress
and regulate metabolism. Altered function of these glands can disrupt
menstruation.
Androgens. In men, androgens are the “male” hormones produced by the
testes which are responsible for encouraging masculine characteristics. In
women, androgens are produced in small amounts by the adrenal glands and
ovaries. Excess amounts of androgens can lead to irregular menstrual periods,
obesity, excessive growth of body hair (hirsutism), and infertility.
Amenorrhea. Absence of menstrual cycles.
Anovulation. Failure or absence of ovulation. May or may not be associated
with amenorrhea.
Atresia. The normal degeneration of eggs and follicles in the ovaries.
Basal body temperature (BBT) chart. A temperature record designed to
detect ovulation by measuring basal (resting) body temperature.
Cervical canal. The passageway leading from the vagina into the uterus.
Cervical mucus. The substance through which sperm must swim in order to
pass the cervical canal and enter the uterus.
Clomiphene citrate. An anti-estrogen drug used to induce ovulation. Brand
names are Clomid® and Serophene®.
Corpus luteum. Tissue formed in the ovary from a mature follicle that has
released its egg at ovulation. The corpus luteum secretes progesterone and
estrogen. The progesterone prepares the lining of the uterus (endometrium) to
support a pregnancy.
Dominant follicle. The largest follicle among the developing follicles in the
ovary.
Endometrial biopsy. A small piece of tissue extracted from the endometrium
for microscopic examination.
Endometrium. The lining of the uterus.
E s t r o g e n. The female sex hormone produced by the ovaries which is
responsible for the development of female sex characteristics. Estrogen is
largely responsible for stimulating the uterine lining to thicken during the
first part of the menstrual cycle in preparation for ovulation and possible
pregnancy. It is also important for healthy bones and overall health. A small
amount of this hormone is also produced in the male when testosterone is
converted to estrogen in fat cells.
Fallopian tubes. The two tubular structures, located one on each side of the
uterus, which pick up the ovulated egg. Sperm and egg usually meet and
fertilize in the tube in normal conception.
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Follicle. Located in the ovary, the follicle contains an egg, the cells that
nourish the egg (granulosa cells), and the fluid secreted by these cells. The
granulosa cells produce estrogen, which in turn acts on the uterus, hypothalamus, and pituitary gland. Estrogen levels rise until the follicle reaches a
mature size, at which time ovulation occurs and the follicle ruptures and
releases its egg. The empty follicle is known as the corpus luteum.
Follicle stimulating hormone (FSH). The pituitary hormone responsible for egg
development. FSH can also be given as a medication. Metrodin® is a brand name.
Follicular phase. The first phase of the menstrual cycle (beginning on the
first day of bleeding) when the developing follicle secretes increasing
amounts of estrogen.
Gonadotropin releasing hormone (GnRH). A hormone secreted in a
pulsatile manner by the hypothalamus that prompts the pituitary gland to
synthesize and release follicle stimulating hormone (FSH) and luteinizing
hormone (LH). Brand names are Factrel® and Lutrepulse®.
GnRH analogs. Synthetic, long-acting hormones similar to the naturally
occurring gonadotropin releasing hormone (GnRH). Brand names are
Lupron®, Synarel®, and Zoladex®.
Human chorionic gonadotropin (hCG). A hormone produced by the
placenta during pregnancy that is often used as a surrogate LH surge with
clomiphene citrate or hMG for the treatment of ovulation disorders. Brand
names are A.P.L.®, Pregnyl®, and Profasi®.
Human menopausal gonadotropin (hMG). A drug used to stimulate egg
development and follicle growth. It contains follicle stimulating hormone
(FSH) and luteinizing hormone (LH), derived from the urine of postmenopausal women. Pergonal® and Humegon™ are brand names.
Hypothalamus. A thumb-sized area in the base of the brain that controls
many body functions, regulates the pituitary gland, and releases GnRH.
Insemination. Placement of sperm via a syringe into a female's uterus or
cervix for the purpose of producing a pregnancy.
LH surge. The surge of luteinizing hormone (LH) that the pituitary gland
releases to trigger ovulation.
Luteal phase. The third phase of the menstrual cycle that follows ovulation
and is characterized by the production of large amounts of progesterone and
estrogen by the corpus luteum.
Luteal phase defect. Abnormality of the luteal phase resulting in inadequate
development of the endometrium.
Luteinizing hormone (LH). A hormone produced by the pituitary gland that
triggers ovulation and stimulates the corpus luteum to secrete progesterone.
Mid-cycle. The second phase of the menstrual cycle in which the LH surge
occurs.
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Mittelschmerz. A pain in the lower abdomen that is associated with ovulation. It is usually related to the rupture of the follicle as the egg is released.
Oligomenorrhea. An abnormally infrequent or light menstrual flow.
Ovaries. The two female sex glands in the pelvis, located one on each side of
the uterus, that produce eggs and hormones including estrogen, progesterone, and androgens.
Ovulation. The release of a mature egg from its follicle in the ovary, usually
occurring on approximately day 14 of a 28-day cycle.
Peritoneum. The smooth transparent membrane that lines the abdominal and
pelvic cavities.
Pituitary gland. The small gland just beneath the hypothalamus in the brain
that stimulates ovarian function by secreting follicle stimulating hormone
(FSH) and luteinizing hormone (LH). Disorders of this gland may lead to
irregular or absent ovulation.
Polycystic ovary syndrome (PCOS). A condition in which the ovaries contain
many small follicles or cysts that are associated with anovulation and
increased secretion of androgens. Symptoms can include irregular or absent
menstrual periods, obesity, and excessive growth of body hair in a male pattern.
Progesterone. A female hormone secreted by the corpus luteum during the
third phase of the menstrual cycle. It prepares the lining of the uterus
(endometrium) for implantation of an embryo and also allows for complete
shedding of the endometrium at the time of menstruation.
Prolactin. A protein hormone secreted by the pituitary gland into the blood.
When elevated, it may lead to absence of menstrual periods and anovulation
as well as the secretion of a milk-like substance from the breasts.
Semen. The sperm and glandular fluid that comes out of the urethra when a
man ejaculates.
Sperm. The male reproductive cells that fertilize a woman’s egg. The sperm
head carries genetic material (chromosomes), the midpiece produces energy
for movement, and the long, thin tail wiggles to propel the sperm.
Thyroid gland. A large, two-lobed, ductless gland located in front of and on
either side of the trachea (windpipe) in the neck that secretes a hormone that
maintains normal body growth and metabolism.
Thyroid hormone. A hormone produced by the thyroid gland that regulates
growth and metabolism.
Ultrasound. A picture of internal organs produced by high frequency sound
waves and viewed as an image on a monitor screen.
Uterus. The hollow muscular organ in the female where a fertilized egg
implants and matures.
Vagina. The canal in the female that leads to the cervix, which leads to the
uterus.
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Let Us Know What You Think
This booklet was written by members of the American Society for
Reproductive Medicine Nurses Professional Group and reviewed by
members of the ASRM Patient Education Committee. Please take a
few moments to fill out the following information and return this card.
I found the Ovulation Detection booklet:
very helpful ______
helpful ______
not helpful ______
I would have liked the booklet to include:
The booklet's readability was:
just right ______ too elementary ______ too complicated ______
I would like to see other booklets of this type about:
Booklets available for purchase through the American Society for Reproductive
Medicine include:
Abnormal Uterine Bleeding
Adoption
Age and Fertility
Birth Defects of the Female Reproductive System
Donor Insemination
Early Menopause (Premature Ovarian Failure)
Ectopic Pregnancy
Endometriosis (Also available in Spanish)
Fertility After Cancer Treatment
Hirsutism and Polycystic Ovarian Syndrome
Husband Insemination
Infertility: An Overview (Also available in Spanish)
Infertility: Coping and Decision Making
IVF & GIFT: A Guide to Assisted Reproductive Technologies
(Also available in Spanish)
Laparoscopy and Hysteroscopy
Male Infertility and Vasectomy Reversal
Menopause
Miscarriage
Ovulation Detection
Ovulation Drugs
Pregnancy After Infertility
Premenstrual Syndrome (PMS)
Third Party Reproduction (Donor Eggs, Donor Sperm, Donor Embryos,
& Surrogacy)
Tubal Factor Infertility
Uterine Fibroids
For copies, ask your physician or contact the ASRM at the address below.
AMERICAN SOCIETY FOR REPRODUCTIVE MEDICINE
Formerly The American Fertility Society
1209 Montgomery Highway
Birmingham, Alabama 35216-2809
(205) 978-5000