Understanding Pregnancy Miscarriage

Peter G. VanDeerlin, M.D., F.A.C.O.G.

Miscarriage is the unplanned loss of a pregnancy prior to the 6th month. Understandably, most women (and their partners) feel disappointment at the abrupt end of their hopes for that pregnancy.

These women often find some solace in the fact that having a miscarriage is fairly common. Many of their friends and acquaintances have likely experienced a miscarriage firsthand because one out of four pregnancies ends in miscarriage.

The rate increases to 50% in women over the age of 41. Pregnancy loss can occur at various times in gestation. It can occur as early as a few days after the missed period. Other times a miscarriage doesn’t occur until after the pregnancy is visualized by ultrasound or even after the fetal heart beat can be heard. It is almost never the case that some inadvertent action on the part of the woman causes the pregnancy loss; however, it’s easy for a woman to falsely blame herself for the miscarriage. We’d like to dispel some of the myths around miscarriage. It is NOT true that working outside the home, carrying heavy groceries, or having sex can cause a miscarriage. We repeat, “The above activities are NOT the cause of a miscarriage.”

So what problems can cause miscarriage? Having a medical illness such as diabetes or lupus can increase a woman’s risk for miscarriage. But most miscarriages are due to a problem with the fetus itself. Studies indicate that up to 70% of pregnancy losses are due to chromosomal imbalances in the fetus.

Chromosomes are the separate packages that contain our genes. Such imbalances are an unfortunate random event which can cause an abnormal pregnancy. However, if a woman has 2 miscarriages in a row and desires to have a baby, it is advised that she seek medical attention from her Obstetrician or a specialist in Reproductive Endocrinology. A fairly simple evaluation may uncover a cause of her repeated pregnancy losses. If the pregnancy loss occurred fairly late (after the 3rd month), then an evaluation is recommended after just one such miscarriage. Abnormalities in the uterus (womb), cervix (mouth of the womb), thyroid hormone levels, blood coagulation, or egg maturation are some of the correctable causes of frequent miscarriages.

The uterus must serve as a safe incubator for the growing fetus. However, some women have a fibroid, septum, or scar tissue inside their uterus which interferes with the proper growth of the fetus. Fortunately, these abnormalities can be removed by a surgical procedure called a hysteroscopy (similar to a D&C), thus allowing the woman to go on and have a normal pregnancy in the future. If a woman was exposed to a medication called D.E.S. when she was in her mother’s womb, she is at risk for having an underdeveloped uterus which can lead to miscarriage. D.E.S. was sometimes prescribed for pregnant women up until the mid 1960’s to prevent recurrent miscarriages. The use of a cervical stitch called a cerclage is sometimes used to decrease the risk of pregnancy loss in these women. A cerclage is also useful in cases where the cervix is too weak to hold the pregnancy in place. This condition is called cervical incompetence. Miscarriages due to this condition occur after 14 weeks of gestation.

An underactive thyroid gland can cause miscarriage. A simple blood test is needed to make this diagnosis, and then supplemental thyroid hormone is prescribed to correct this matter. Another series of blood tests that should be offered is to check for unusual blood clotting tendencies that can lead to problems with the blood vessels near the placenta which nourishes the fetus. This tendency to form blood clots can be due to either inherited clotting abnormalities or from the development of specific antibodies in the blood stream called anticardiolipin antibodies.

Fortunately, once the diagnosis is made, treatment can be initiated with future pregnancies in order to reduce the chance for another miscarriage. Checking the chromosomes of the woman and her partner is another test that is frequently offered to patients who have had recurrent miscarriages. It can detect cases where the man or woman has one chromosome that is attached to one another. In that setting there is a roughly 50% chance for the fetus to inherit an unbalanced set of chromosomes, which is a situation not compatible with continued fetal growth. If one of the prospective parents has this condition, there is a therapy which we have successfully used to dramatically lower the risk of miscarriage. This therapy is called Pre-implantation Genetic Diagnosis - or PGD for short. The process requires In Vitro Fertilization (IVF) to obtain embryos which can be tested to see if they have the correct number of chromosomes BEFORE they are returned to the womb.

Some women do not reliably ovulate (release an egg) each month. These women often have a subtle case of polycystic ovarian syndrome (PCOS). When these women do ovulate, the egg is often not fully ripened - leading to an embryo that is more likely to stop growing. The adequacy of ovulation is usually tested through a blood test for progesterone a week after ovulation.

In at least half of couples who undergo an evaluation for recurrent miscarriages, there is no identifiable cause. The good news is that these couples have an excellent chance for having a normal baby with their next pregnancy. Their chance for a normal pregnancy is very similar to that of a couple who has never had a miscarriage. So our advice for such couples is to try again and not to lose hope. It is safe to try to conceive again 2 months after a miscarriage (sometimes even sooner if the loss was very early). Future pregnancies can be monitored closely with hormone assays and early sonograms. If another miscarriage occurs, we recommend that any miscarriage tissue (passed spontaneously or obtained at the time of a D & C) be examined for a chromosomal imbalance. A positive finding of an imbalance will give the couple the answer to the question, “What went wrong this time?” What else can a woman do to help avoid another miscarriage? She should follow common health guidelines such as avoiding smoking and limiting caffeine intake to no more than one beverage a day. Even before a woman wants to try to conceive she should take a daily vitamin containing folate which is critical for the early growth of the embryo. Your physician will tell you if you need other special medication like progesterone or baby aspirin. Most treatment is individualized depending on the specifics of the case.

Though miscarriage can be emotionally devastating, it is a common occurrence, and there is a very high chance that the next pregnancy will be normal. Your concerns can often be alleviated by asking your doctor. Therapy is sometimes recommended and is usually successful.


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