Commonly considered by many as a miracle, pregnancy and childbirth require many pieces of a puzzle to all fit together perfectly. The way the human body functions to create and bring life into the world is awe-inspiring and remarkable. One part of this conception puzzle is ovulation, the release of a mature ovum from the ovary.
Before understanding why ovulation is so important for conception, it is imperative to understand some of the basic reproductive functions in a woman. Menses is the shedding of the lining of the uterus, the endometrium, so that each potential new pregnancy has a new uterine lining. The typical menstrual cycle is 28 days, but can normally be 26 days, or even 35 days.
The ovary controls the menstrual cycle, which has three distinct phases. The first phase, the menstrual phase, makes up the days when a woman menstruates, on average five days. The second phase, the follicular phase, takes place from the last days of menstruation through ovulation, and is when the follicles of the ovary develop and the lining of the uterus grows. The final phase, the luteal phase, occurs from ovulation, when the egg is released, to the next menses or a pregnancy.
For ovulation to occur, the ovary must send a signal to the pituitary gland in the brain to release the luteinizing hormone (LH). As Dr. Ron Thompson explains, the LH promotes the final 24 to 36 hours of maturation of the ovum for ovulation. “During the follicular phase, the ovum develops in a small, ever-enlarging sac of fluid in a follicle on the outer surface of the ovary,” Dr. Thompson states. “At ovulation, the mature ovum leaves the follicle, enters the distal fallopian tube and waits for conception.”
After ovulation, the place where the ovum left the follicle transforms into the corpus luteum, or yellow body. The corpus luteum produces progesterone, the hormone of pregnancy. If conception occurs, the embryo implants into the lining of the uterus into the endometrium.
“The placenta of the early embryo, the chorionic villus, produces Human Chorionic Gonadotropin,” said Dr. Thompson. “The HCG circulates in the bloodstream and stimulates the corpus luteum to produce progesterone for about 12 weeks, until the placenta can produce its own progesterone to support the pregnancy.”
Pregnancy tests measure the HCG produced by the early embryo to determine whether a woman is pregnant or not. The HCG value typically doubles every two to three days, which is why taking a pregnancy test later produces more accurate results, explains Dr. Thompson.
After understanding how ovulation occurs, it is important to understand when ovulation occurs. The timing of sexual intercourse with ovulation is crucial for conception. A woman’s corpus luteum typically lasts 14 days, which means if she has a normal 28-day menstrual cycle, she will ovulate on day 14. If her menstrual cycle is 35 days long, she ovulates on day 21.
A woman can figure out when she ovulates by subtracting 14 days from the expected day of her next menstrual period and have sexual intercourse to correspond with the time of ovulation. This assures that all the pieces of the puzzle work together to achieve pregnancy.