During a girl’s fetal life, the ovaries contain hundreds of thousands of eggs, which are scattered around in the connective tissue of the ovary. Most of these eggs disappear prior to birth. As she grows older some of them are surrounded by specialized cells that eventually form a capsule called the follicle, much like the shell of a hen’s egg. As sexual maturity approaches, the pituitary gland, under the stimulation of GnRH from the hypothalamic part of the brain, begins to secrete follicle stimulating hormone, FSH.

Under the influence of FSH, some of the follicles now develop a fluid, and those that are near the ovarian surface may bulge through the surface. These are called graafian follicles. In an entirely random manner, one or, at most, a few grow far larger than the rest. This growth begins during menstruation, and is called the follicular phase of the ovarian cycle. Follicles that do not grow simply shrivel and disappear. The follicular stage of the ovarian cycle, which takes place simultaneously with the menstrual and proliferative phases of the endometrial cycle, is variable in length.

Ovulation

When a certain level of growth is reached, the graafian follicle falls under the influence of another hormone from the pituitary gland ­ luteinizing hormone or LH. At midcycle there is a surge of LH, which follows the peak of estrogen secretion by about 24 hours-see the graph on page 15. LH stimulates further development of the follicle until, within 12 to 36 hours of the LH surge, it bursts through the surface of the ovary and pops the egg with its surrounding mantle of follicle cells into the waiting folds of the fallopian tubes. This is called ovulation. From the estrogen peak to actual ovulation is considered the ovulatory phase of the ovarian cycle.

In humans, ovulation is totally independent of sexual intercourse, occurring with equal frequency in the sexually developed virginal woman and the sexually active woman. If fertilization does not occur obviously its occurrence is relatively infrequent the tiny unfertilized egg quickly dies and fragments into many pieces, which white blood cells then eat up.

The Luteal Phase

Following ovulation, the follicle walls fall inward and, under the influence of LH, the follicle changes into the corpus luteum. The corpus luteum secretes some estrogen, but more progesterone. This phase of the ovarian cycle is termed the luteal phase. The luteal or progesterone­dominant phase of the ovarian cycle corresponds in its timing to the secretory phase of the endometrial cycle. It is relatively constant in length, varying from 12 to 16 days in all women.

When a woman becomes pregnant, the corpus luteum will remain viable for several months, secreting progesterone necessary to maintain the pregnancy. The corpus luteum is maintained by human chorionic gonadotropin (hCG). (In medical literature, a lower case “h” is often used to distinguish naturally occurring human hormones from synthetic ones.) Human chorionic gonadotropin is a hormone secreted first by the fertilized egg, starting about 6 days after fertilization, and later by the placenta. The chorion is the layer of the embryo from which the placenta and the outer of the two fetal membranes develop.

When a woman does not become pregnant-which is true for most of her cycles-the corpus luteum will regress, progesterone levels will then drop, and the menstrual flow will begin.

The elegant interplay and miraculous coordination of multiple mechanisms to make reproduction work successfully is a source of cease­less amazement. Many more eggs are fertilized than babies born. Fertilization, implantation, and early development of the ovum are each so complex that something frequently goes wrong and further growth ceases. If this occurs within the first 10 to 12 days, the menstrual period is not even late. If development of the ovum is arrested, say, around the fifteenth day, the menses are delayed a week or so but no recognizable tissue is passed. However, if pregnancy progresses several weeks before it comes to a halt, a discernible miscarriage occurs. Some experts believe ,hat at least 40 to 50 percent of fertilized eggs never end up as a baby.

• Menstrual
• Proliferative
• Secretory

Each phase is controlled by the hormones discussed in the previous section.

The Menstrual Phase

Because we count the beginning of the reproductive cycle from the first day of menstruation, this phase begins the endometrial cycle. Menstruation is the shedding of the lining of the uterus that had been built up during the previous two phases. As the ovarian corpus luteum slows and stops functioning, secretion of estrogen and progesterone decreases. In response to the dropping levels of these hormones, the blood vessels of the endometrium go into spasm, there is oxygen loss to the tissue (necrosis), and the lining sloughs off. Menstrual flow consists of blood, mucus, and cells from the lining of the uterus. No other organ in the body sheds and regenerates cyclically for years as does the uterus.

Menstruation usually lasts between 3 and 6 days, although it can be shorter or longer. Following menstruation, the proliferative phase of the endometrial cycle begins.

The Proliferative Phase

During this phase, under the influence of estrogen secreted by the ovarian follicle as it matures, the endometrium, which is thin following menstruation, begins to thicken. Cells lengthen, blood vessels reform in the endometrial lining, and glands grow or proliferate. The height of the endometrium grows from .5 millimeter to as much as 5.0 millimeters. This is important as the endometrial height can be measured via sonogram; and beyond 5.0 millimeters may indicate a problem known as endometrial hyperplasia. If not treated, over time this condition can lead to cancer of the endometrium. An endometrial biopsy in which a sample of the tissues of the endometrium is taken via a tiny suction tube provides a more definitive diagnosis. The proliferative phase is variable in length from woman to woman and from cycle to cycle in the same woman. It may last from 7 to 21 days.

The Secretory Phase

Once ovulation has occurred, progesterone becomes the dominant ovarian hormone as it is the main hormone secreted by the newly created corpus luteum-formed from the follicle through which the egg just ruptured. Under the influence of progesterone, the endometrium enters its secretory phase. This phase is consistently 12 to 16 days long. During this phase, the endometrium continues to thicken, blood vessels grow and open, and glands grow and secrete a fluid rich in glycogen (sugar). As many as fifteen thousand endometrial glands open onto the endometrial surface during the secretory phase of the cycle. The lining of the endometrium becomes more dense, but growth in height is inhibited.

From each testicle the spermatozoa slowly pass upward through the epidiymis.The trip through the ducts requires 2 to 4 weeks, the spermatozoa maturing as the journey progresses.

Spermatozoa do not make their own way up the male ducts, since they are motionless at this stage, but are propelled upward by imperceptible contractions of the muscular tissue forming the walls of the epididymis and vas. It is only after the mass of sperm cells is diluted during orgasm by fluid from the prostate and other male glands that they are thrown into vigorous movement. Spermatozoa remain actively motile for as long as 72 hours in the upper reaches of the female reproductive tract.

The Journey of the Egg Down the Tube

After ovulation, the egg, having passed from an ovary into the fallopian tube, travels down the five-inch tube. The muscular walls of the tube encircle a canal that is wide at the ovarian end and narrow at the uterine end. The diameter of the tube at the uterine end is as small as a single broomstraw. Although it would make sense that an egg released from the left ovary would be picked up by the left tube, women who have had one tube and the opposite ovary removed have been known to achieve pregnancy, attesting to the remarkable action of the tubes .

The mechanism that propels the egg downward through the tube toward the uterus seems to be a combination of fluid currents and rhythmic muscular contractions. Many of the cells lining each fallopian tube are ciliated they possess hairlike projections from the surface that beat vigorously. Under the microscope, they look like a field of wheat being blown by the wind. The beating of the cilia causes a fluid current that mostly flows down the tube from the ovarian end toward the uterine end. When the ovum is ovulated from a ripe ovarian follicle, it is surrounded by a thick, loosely adherent covering of some three thousand small cells, the cumulus cells that envelop the egg completely during its residence in the follicle. Some of the cells are brushed loose by the egg’s contact with the sides of the tube, especially with the ciliated cells of the tubal wall.

Sperm Motility and Fertility

If the male does not ejaculate for some time, the spermatozoa that complete the journey from the testes are stored in the ducts and epididymis and may suffer effects of aging, The first ejaculation after a long interval, therefore, may produce cells of impaired motility, For this reason, physicians and midwives recommend frequent inter course ­optimally, every 24 hours during the days immediately preceding ovulation-for most couples desirous of pregnancy who are having difficulty in conceiving,

Fusion of the Two Nuclei

Once the sperm has entered the cytoplasm of the ovum, its head en­larges to form what is called a pronucleus-the nucleus of the mature sperm cell. The ovum also completes its final maturation after entry of the sperm, also forming a pronucleus. Both the male and female pronuclei enlarge and migrate toward the center of the cell. The membranes of each pronucleus disintegrate, and the two nuclei fuse into one nucleus. When this has been accomplished, fertilization is completed. The fertilized ovum now has forty six chromosomes twenty three from the father and twenty-three from the mother. It has become a zygote.

Cleavage-or rapid cell division-ensues within 30 hours of fertilization.The fertilized ovum divides into two cells, the two cells divide into four, the four into eight, and so on, creating-after an average of 266 days from the moment of fertilization or 280 days from the beginning of the last menstrual period-a fully developed baby, weighing from 5½ to over 10 pounds.

The Three Stages of Pregnancy

Fertilization is a two-part process that begins when the spermatozoon or sperm cell enters the ovum or egg cell, it is completed when the nuclei of the male and female cells (called pronuclei) unite.

Conception is the onset of pregnancy marked by implantation of the fertilized ovum. These two processes lead to pregnancy.

Pregnancy is the condition of having a developing embryo or fetus in the body after successful conception.

Legumes -  mainly dried beans, peas, and lentils are deficient in tryptophan and methionine. The nuts and seeds such as sunflower seeds, peanuts, and sesame seeds lack lysine and isoleucine.

Complete proteins can be ensured through the following combinations -

• Rice and legumes
• Corn and legumes
• Wheat and legumes
• Wheat and peanuts and milk
• Wheat and sesame and soybeans
• Rice and brewer’s yeast
• Beans and corn
• Soybeans and rice and wheat
• Soybeans and peanuts and sesame
• Soybeans and peanuts and wheat and rice
• Peanuts and sesame and soybeans
• Sesame and beans
• Sesame and soybeans and wheat
• Sesame seeds or Brazil nuts or mushrooms and: green beans, lima
• Beans, brussels sprouts, cauliflower, or broccoli
• Greens and millet or rice

The additional protein requirement of pregnancy can be satisfied with the following food choices in a vegan diet, while increasing the caloric intake by 300 calories -

• 2 cups soy milk (plain)
• 9 ounces tofu
• 3 ounces tempeh
• 1 cup cooked beans

Since vegans do not eat dairy, they need to get calcium from other sources. These might include calcium-fortified soy milk or orange juice with calcium. Greens, such as broccoli and kale, have calcium, but it is hard to get enough from these sources. Tofu can be made with calcium sulfate or carbonate. Blackstrap molasses, tahini, and figs all have calcium. Depending on the amount of dietary calcium, a supplement may be advised. The recommended dosage is 1,200 mg (in divided doses of 300 or 600 each) and 10 micrograms (400 IUs-International Units) of vitamin D daily.

Because vitamin B12 is found only in animal sources of foods, a 4 microgram supplement of vitamin B12 is advised for people on vegan diets. If soy milk is used, the need for supplementation depends on whether or not the milk is fortified with these nutrients. Other sources of vitamin Bl2 are fortified cereals and yeast powder. Red star vegetarian support formula has been tested for active Bl2. One teaspoon of yeast powder should provide the day’s requirement of this vitamin for women on a vegan diet.

Some pregnant women are accustomed to following special weight loss diets such as high protein, low carbohydrate diets. Others follow restrictive diets such as the macrobiotic diet. These are too limited for pregnancy and should be modified to include foods from all the groups.

• Keep track of the first day of every menstrual period so you always know your last one should you become pregnant.
• Have a preconception care visit several months before planning a pregnancy
• Seek early prenatal care as soon as you believe you are pregnant.

The Effect of Prolonged Pregnancy on the Fetus

When a pregnancy is genuinely prolonged beyond 42 weeks, there is a chance that the welfare of the fetus may be jeopardized, Prolonged pregnancy may result in a condition known as placental deficiency or uteroplacental insufficiency-in which the placenta ceases 1:0 function well enough to supply the fetus with needed oxygen. Many such fetuses tolerate the stress of labor poorly. They often ‘lave diminished amniotic fluid, decreasing the cushion they need to Withstand contractions, They are prone to pass meconium (the thick green material that fills the fetal large intestine) into the amniotic fluid, making a dense mixture, They tend to gasp in response to the stress of uterine contractions and thus to breathe in the meconium, Meconium is very irritating to the lung tissue and breathing it in can “result in respiratory difficulty after birth.

Some babies born after 42 weeks gestation develop “post maturity ­syndrome.” These babies lose some of the fat under their skin so they appear thin, Their fingernails are characteristically long, They often lose the protective creamy coating on the skin called vernix caseosa, as well as the fine hair covering the newborn’s body, called lanugo. This makes their skin dry, peeling, and unusually wrinkled, They are born with an especially alert look.

When pregnancy is prolonged, with the possibility of post maturity a number of tests are utilized to check the baby’s well-being.These tests are fully described in Chapter 17. When midwives or family physicians have been the primary providers for the pregnancy,an obstetrician should be consulted after 42 weeks. If there is any question about whether the baby is in danger, labor usually will be induced.

Cesarean delivery is not a treatment for a postdates pregnancy unless fetal assessment has given evidence of serious fetal distress, indicating that induction will be dangerous to the fetus, or when a planned induction does not succeed,