Stress May Up Early Miscarriage Risk

Feb. 21, 2006 -- During early pregnancy, miscarriage may be more likely among women with high levels of the stress hormone cortisol.

That's according to a study published online in the Proceedings of the National Academy of Sciences.

The study shows that miscarriages during the first three weeks of pregnancy were nearly three times as common among women with high cortisol levels, compared with women with normal cortisol levels.

Bigger studies are needed, but high cortisol levels might be a sign that women's bodies aren't prepared to carry a pregnancy to term, write Pablo Nepomnaschy, PhD, and colleagues.

Nepomnaschy worked on the study while at the University of Michigan and is now with the National Institute of Environmental Health Sciences.

Pregnancy Study

Most miscarriages happen very early during pregnancy. Some miscarriages are due to health problems with the mother or fetus. Others don't seem to have an obvious cause.

Maternal stress is often blamed for "unexplained" miscarriages, but little scientific research has been done to check that idea, the researchers write.

They studied 61 married women aged 18-34 in a small community in rural Guatemala. The women, who already had other children, gave urine samples three times weekly to screen for pregnancy and check cortisol levels. At the beginning of the study, the women's baseline cortisol level was measured while not pregnant. If the cortisol level went above that baseline, it was considered "increased." If it stayed the same, it was considered "normal."

Over a year, 16 of the women had 22 pregnancies. Nine pregnancies were carried to term; 13 were lost.

The study only focused on the first three weeks after conception. It also doesn't include the women's possible sources of stress.

Higher Miscarriage Rate

Among the findings:

• Miscarriages were 2.7 times more likely among women with increased cortisol levels.
• Miscarriages happened after an average of about two weeks of pregnancy.
• 90% of women with high cortisol levels miscarried in the first three weeks of pregnancy.
• 33% of women with normal cortisol levels miscarried in the first three weeks of pregnancy.

Adjusting for factors that could affect cortisol levels didn't change the results, write Nepomnaschy and colleagues.

Did cortisol contribute to the miscarriages, or did cortisol levels rise before miscarriage for other reasons? The researchers aren't sure, so they call for bigger studies on the topic.