Getting Pregnant For Dummies. Sharon Perkins

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СКАЧАТЬ is your uterus.” Much has been said about the position of the uterus, but in reality, it makes no difference. Most women have a uterus that points to the pubic bone, which is considered the normal position (also called an anteverted uterus). Twenty percent of women have a uterus that points toward their back (called a “tipped” or retroverted uterus), which, contrary to what many women believe, does not cause problems getting pregnant. However, the real situation is that when a woman is in the upright position, the uterus is parallel to the floor. Since primitive humans were upright most of the time, this is the natural opposition of the uterus and only when gynecologists started examining women lying down did this become an issue. Mother nature probably could care less which way the uterus faces.

      Abnormalities that can affect fertility

      

Around 2 to 3 percent of women have a uterus that is abnormal in its size, shape, or structure. The uterus starts as two separate tubes, which should then join. Once joined, the wall separating the two tubes is dissolved. Sometimes errors in the shape of the uterus occur because there was a failed joining of the tubes (fusion defects) or because the wall does not dissolve (canalization defects). It’s hard to know how many women have uterine anomalies because most women do not have tests to determine the shape of their uterus, so the occurrence will be different for women without infertility and infertile patients who undergo testing. The most common uterine anomaly is the arcuate uterus, which is a very mild fusion problem. The very last part of the tubes fails to join, leaving a somewhat heart-shaped uterus. This type of uterine anomaly does not impact fertility or miscarriage, but it is reported whenever imaging of the uterus (usually using ultrasound) is done — which can cause concern if no one tells you that this is not an important finding. It’s like distinguishing brown eyes from blue eyes; interesting but not predictive of infertility.

The most common variation in the shape of the uterus that can impact fertility and miscarriage rate is caused by a canalization defect and called a septate uterus, which means that a band of tissue (septum) partially or completely divides the inside of the uterus. This is a congenital condition that occurs while a female fetus is developing in utero when the wall is not properly dissolved. It can affect all or part of the wall so there are many variations on how much of a septum occurs. Septate uterus occurs in multiple forms in less than 3 percent of all women. Fusion defects can create a uterus with two horns (bicornuate) or two separate uteri or even two cervices and two vaginas. Sometimes only one tube forms and thus only one side of the uterus develops, and there is no fallopian tube on that side since the fallopian tubes also develop from the initial tube. This is called a unicornuate (one horn). Depending upon the extent of the abnormality, women who have bicornuate and unicornuate uteri usually do not have problems conceiving or keeping a pregnancy. Fusion defects may result in pregnancy complications such as premature labor or malpresentation of the fetus such as a breech. Treatment for uterine defects depends upon which defect is present, the pregnancy history of the woman, and how severe the defect is. In general, only canalization defects are treated, and these require surgery.

      Even if the shape of your uterus is normal, it may contain some unwanted “accessories” — growths such as polyps and fibroids — which may decrease the chance that an embryo can implant and grow in your uterus. These are easily diagnosed by a transvaginal ultrasound and/or an MRI and are not always an issue depending upon where they are located in the uterus. If placement is a problem for an implanting embryo, they can be removed before trying to get pregnant. Polyps are easily removed and don’t cause any complications after they’re gone. Removing fibroids may be more complex. Small ones may be removed through the vagina by entering the uterus through the cervix in an outpatient surgicenter, but large ones may require an abdominal incision and a hospital stay of a couple of days. Removing fibroids can leave scar tissue in the cavity that can make it harder to get pregnant because the fetus won’t be able to implant in the scarred area. In rare cases, you may also need a cesarean section after fibroid removal.

      Scar tissue can also form in your uterus after a dilation and curettage (D&C for short) for problems like retained tissue after a delivery or miscarriage. If there’s a lot of scar tissue, nearly filling the uterus, it’s called Asherman’s syndrome. Obviously, the more scar tissue, the harder it becomes to achieve a pregnancy. The scar tissue can be removed surgically, which may increase your chance of achieving a pregnancy. Commonly, the surgery will need to be repeated until enough of the scars have been removed.

      The ovaries

      Most women have two ovaries, which contain the most important accessory of all — eggs! How many eggs? Less every year, since every day of your life, eggs are lost through atresia, which means that they die off because they’re not being stimulated to mature. For example:

       Before birth, a girl fetus’s ovaries contain around 6 to 7 million eggs. The production of eggs stops when the fetus is near five months.

       A newborn baby girl’s ovaries contain about 2 to 3 million eggs.

       By puberty, only 300,000 to 400,000 eggs remain.

       Every month, 500 to 1,000 eggs are recruited from the resting pool and start down the path to maturity where they are capable of creating a normal embryo. This path takes over five months, and many eggs are killed by the ovary along the way. When a woman starts her period only about 20 to 30 remain, and in the next two weeks only one will emerge as the best egg. This egg is the one that is ovulated.

       By a woman’s late 30s, only 25,000 or so eggs remain.

       By age 50, only 1,000 or so eggs remain, and many are chromosomally abnormal because of the impact of aging on egg quality.

      The eggs

      You may wonder what eggs contain to make them into your potential screaming newborn. The answer is chromosomes — 23 chromosomes, to be exact. Each chromosome contains the genes that determine whether your baby is tall or short, blond or brunette, and, to some extent, fat or thin. The egg also contains considerable machinery necessary to mix the male and female chromosomes and then divide the chromosomes into the correct number for each daughter cell that results from the first cell division that the fertilized egg undergoes.

      

Of course, there’s more to an egg than chromosomes. Three protective layers surround the egg, starting with the cumulus layer. That’s the nourishing and protecting fluffy layers of cells that completely surround the egg. Moving inward, you’ll see the corona radiate, the protective single layer of cells covering the zona pellucida, the “shell” of the egg. A mature, ready-for-fertilization oocyte, or egg, has a small attachment called a polar body, which is the remnant left after the egg divides (a process called meiosis) so that it contains only 23 chromosomes. The polar body also contains 23 chromosomes.

All cells in the human body besides eggs and sperm have 46 chromosomes. Eggs and sperm each have 23, so the baby they create has 46.

      Each month, one egg is released from one of your ovaries. The decision about which one ovulates (right or left) is random; they do not necessarily alternate. If you have only one ovary, either because you were born that way or because one was surgically removed, your one ovary generally takes over egg making each month so that you still ovulate each month.

      The fallopian tubes

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