Miscarriage and PCOS - Is There Increased Risk?
The evidence tends to be conflicting on the subject of miscarriage risk in women with PCOS. A large number of studies have been done and each study has its strengths and weaknesses. It has been confirmed that there is a link between PCOS and infertility, and there are some indications that certain aspects of PCOS can influence miscarriage.
PCOS, What it Is and What it Does
PCOS is a condition in which a woman's ovaries and in some cases, the adrenal glands, produce more androgens (male hormones) than normal. It is the most common cause of female infertility related to anovulation - that is the absence of ovulation. The fact is that most women don't know they have PCOS until they try to conceive and are unsuccessful. Menstrual and ovulatory irregularities that can lead to infertility are common in women with PCOS. Most women with infertility related to PCOS can be treated and do become pregnant. However, some women with infertility related to PCOS do not respond to treatment and do not become pregnant.
Does PCOS Cause Miscarriage?
Although it is reported that some studies indicate the incidence of miscarriage in women with PCOS is as high as 45%, there is conflicting evidence. A study completed in 2003 by Schieve and colleagues who analyzed 62,228 pregnancies achieved with ART determined that the overall miscarriage rate among women with PCOS was 14.7%. This risk was no different from the average miscarriage rate of all the other groups. In this case, those who conceived did so through assisted reproduction techniques, which carry an increased number of incidents of miscarriage than normal conception in healthy women.
It is important to remember that the estimates of incidence of miscarriage vary since many women who miscarry do so without even knowing they were pregnant. It is estimated that one in four pregnancies (25%) end in miscarriage, most of them during the first trimester of pregnancy.
The Hormonal Connections
Some reasons for miscarriage that may apply more to women with PCOS revolve around hormones, since PCOS wreaks havoc with a woman's hormones. Women with hormonal irregularities may find it more difficult to conceive and, when they do it seems they are more likely to miscarry. One of the dominant features of PCOS is multiple hormonal imbalances with some hormone levels being very high while others are very low.
The web of hormonal interfacing affects the timing of the release of an egg from the ovaries. Women with PCOS often suffer with anovulation, no egg released, or the timing of their ovulation is skewed and unpredictable. Luteal phase defect (LPD), elevated luteinizing hormone levels, and insulin resistance are all possible issues for women with PCOS who are trying to become pregnant or who are experiencing difficulties with their pregnancies.
Luteal Phase Defect and PCOS
The luteal phase of the menstrual cycle is the time between ovulation and the onset of menses - the second half of the period. Luteal phase defect essentially means that the lining of the uterus is not in the right phase of development at the right time and so the implantation of a fertilized egg is prevented, or the embryo can't attach because the lining is too thin.
LPD may be caused by (among other things) an excessive amount of luteinizing hormone (LH) too early in the cycle or an improperly timed LH surge. A situation called LH hypersecretion tends to happen in women with PCOS who have elevated LH during the follicular phase (the first half) of the cycle. Signals to release the egg from the follicle are sent out too soon and the egg dislodges from the supporting cells prematurely causing a pause in maturation. This interruption is thought to result in abnormal chromosomes in the egg, a condition that increases the risk of miscarriage.
Insulin Resistance is a Known Cause of Miscarriage
Insulin is another hormone that is linked both to miscarriage and to LH. Some women with PCOS have insulin resistance, a situation that requires excessive amounts of insulin to control blood sugar levels. High insulin levels stimulate production of LH and testosterone, both of which are linked to poorer egg quality and ultimately to miscarriage. Insulin resistance does have a link to recurrent miscarriage.
When these factors are considered, it is possible to see how the risk for a woman with PCOS can be higher when it comes to conceiving a pregnancy and carrying it to term.
Learn more about the causes of miscarriage on our site.