Miscarriage. It is a difficult subject, that is rarely discussed among friends and family, even though it occurs with surprising frequency. According to the March of Dimes, as many as 50% of all pregnancies end in miscarriage – most often before a woman misses a menstrual period or even knows that she is pregnant.
Recurrent miscarriage, which is defined as a sequence of two or more spontaneous pregnancy losses, is much less common, with an estimated occurrence of 1%. Further evaluation is recommended when a woman has three or more miscarriages. So what are the most common causes of recurrent miscarriage?
- Approximately 60% of miscarriages result from an embryo having an incorrect number of chromosomes. By and large, this occurs randomly, though it becomes more common as a woman gets older.
- In approximately 3% of couples that have had recurrent miscarriages, one partner has been found to be a carrier of a balanced translocation. If you think of your chromosomes like a set of encyclopedias, a balanced translocation is like taking a chapter out of volume B and putting it in volume M, while putting the chapter you took out of volume M into the spot previously occupied by the chapter from volume B. All the material is still there, just in a different place. Therefore, the person with a translocation has no ill effects from this switcheroo , but when they pass their genetic information to their offspring, their children can receive extra or missing material. This can lead to any number of issues including, but not limited to, miscarriage.
- Another possible cause of recurrent miscarriage is a congenital anomaly of the uterus. Examples include a septate uterus, adhesions and scarring of the uterus, an incompetent cervix, fibroids, and polyps.
- Women with certain medical conditions may also have an increased risk for recurrent miscarriages. Antiphospholipid syndrome, diabetes mellitus, thyroid conditions, and polycystic ovarian syndrome are all relatively common potential causes in this category.
Unfortunately, health care providers cannot determine an etiology in 50-75% of women with repeated miscarriages.
If you are experiencing recurrent pregnancy losses, fear not. Though the percentages may seem daunting, here’s another that may offer hope: approximately 65% of women with unexplained miscarriages have a successful next pregnancy. To increase the odds that you are within that percentage, talk to your OBGYN about your pregnancy history to determine the best next step for you.