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 writ- ten 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. AMERICAN SOCIETY FOR REPRODUCTIVE MEDICINE 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 tradi- tional conception to occur, the man must ejaculate his s e m e n, 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 i n f e r t i l i t y, it is often necessary to determine whether or not a woman i s ovulating. There are several ways to detect ovulation, including the basal body t e m p e r a t u re (BBT) chart, urine test kits to measure luteinizing hormone ( L H ) levels, vaginal u l t r a s o u n d, 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 surg e 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. 3 Uterus Fertilization Usually Occurs Here Ovary Cervix Egg Released Fallopian Endometrium Cervical (ovulated) Tube Mucus 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 underg o ovulation or at re s i a (degeneration). Ovulation is a complex sequence of events involving hormones from the h y p o t h a l a m u s , p i t u i t a ry, and th y ro i d g l a n d s , including g o n a d o t ropin 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. 4 The menstrual cycle is divided into three phases: the follicular phase, m i d - c y c l e, 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 d o m i n a n t f o l l i c l e to mature. The dominant follicle increases in size and secretes es t ro g e n 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 break- down of the endometrium, which results in menstruation. A b n o r m a l progesterone secretion may be caused by poor follicular development, inade- quate 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 us u a l l y 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. 5 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— b. Nearing the cerv i c a l o v u l a t i o n — t h e mucus is sticky c e rvical mucus and does not extends a little s t re t c h . b e f o re bre a k i n g . c. Just before d. A f t e r o v u l a t i o n — t h e o v u l a t i o n — t h e c e rvical mucus is c e rvical mucus v e ry thin, watery, becomes thick and stre t c h a b l e . a g a i n . 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: 6 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.