Stress in early pregnancy can cause miscarriage

Feb 22 2006

According to a team of researchers in the U.S., women who exhibit signs of stress are three times more likely to miscarry during the first three weeks of the pregnancy.

In a recent study lead author Dr. Pablo A. Nepomnaschy, from the National Institutes of Health in Research Triangle Park, North Carolina, and his colleagues examined the levels of a hormone in the urine of 16 women in a rural Guatemalan community.

The urine was checked three times a week for a period of one year for the stress induced hormone cortisol.

The study is the first to link increases in cortisol levels to very early-stage pregnancy loss.

According to previous scientific reports anywhere from 31 percent to 89 percent of all conceptions result in miscarriage, but most studies begin when women notice they are pregnant, about six weeks after conception.

However, most miscarriages are known to happen during the first 3 weeks of pregnancy and Nepomnaschy says the only way to capture the first three weeks of pregnancy is to begin collecting their urine from before they become pregnant.

In the study, 22 pregnancies occurred in a total of 16 women, and each woman’s cortisol levels were measured against their own baseline levels.

The researchers found that 90 percent of the women, whose ages ranged from 18 to 34, with elevated levels of the stress-induced hormone miscarried during the first three weeks of pregnancy, compared to 33 percent of those with normal levels.

The researchers say the body may recognize elevated cortisol levels as an alarm that conditions are unfavorable for pregnancy.

The previous studies which focused on later pregnancy stages did not find an association between elevated cortisol and miscarriage, and Nepomnaschy and colleagues speculate that stress may be more likely to lead to loss during the earliest stages of pregnancy, while the embryo is just beginning to develop.

They do say however that more research is needed before definitive conclusions can be arrived at.

Nepomnaschy his colleagues say though it is unclear if cortisol is directly involved with the miscarriages or if it signals some other mechanism in the body that causes the miscarriage, the results are consistent with a 2004 study in which he and his colleagues found that elevated cortisol levels were associated with lower progesterone levels - a hormone that prepares the uterus for the implantation of the fertilized ovum.

The fieldwork was conducted while Nepomnaschy was a PhD student at U-M, both at the Anthropology Department and the School of Natural Resources and Environment.

He is now a post-doctoral fellow at the Epidemiology Branch of the National Institute of Environmental Health Sciences.

The research is published in the Proceedings of the National Academy of Sciences.