— Women who are unmarried or not living with a partner have a significantly higher risk of miscarriage, according to a new study. And undergoing a divorce or separation during pregnancy raises the risk still further, a new study has found.
Stress may be to blame, the researchers say. Women who experienced more than two stressful or traumatic events during pregnancy had treble the risk of miscarriage than their "stress free" counterparts.
Previous studies have also linked stress to miscarriage (see Stressed mothers may risk early miscarriage). Stress might cause miscarriage by disrupting the hormonal pathways that influence the inner lining of the womb, experts say.
The new study featured nearly 7000 women, 600 of whom miscarried during the first trimester. Women living separately from their partner, or who had no partner, were 73% more likely to miscarry. And women pregnant by a man different from the father of their previous children had a 66% higher risk of miscarriage than those carrying a second baby from their same partner.
Women who switch partners might have a higher rate of miscarriage because they have had unstable relationships and, as a result, experienced stress, suggests Pablo Nepomnaschy of the National Institute of Environmental Health Sciences in North Carolina, US, who was not involved in the study.
Fruit and veg
Previous work has estimated that about one in five pregnancies end in miscarriage, says Pat Doyle of the London School of Hygiene and Tropical Medicine, UK, who led the study. Certain health conditions, such as blood-clotting disorders, are well-known risk factors for miscarriage. But causes of most miscarriages remain a mystery, Doyle says.
Being underweight was also found to be a risk factor in the study. Women with a body mass index (BMI) lower than 18.5 had a 72% increased chance of miscarriage, compared to those women with a normal BMI, of 18.5 to 24.9.
Vitamin supplements could improve the chances of a normal pregnancy among underweight women, Doyle suggests. Her study found that, in general, women who took vitamins or ate fruit and vegetables daily had roughly half the number of miscarriages compared to those with less healthy diets.
Unexpectedly, Doyles team did not find that obesity increased the risk of miscarriage early in pregnancy.
The researchers say that more studies are needed to establish these links and to explore the following additional findings of their study:
The widely-help belief that morning sickness is the sign that the pregnancy is progressing well was supported nausea and sickness were linked to a 70% reduced risk of miscarriage.
Daily consumption of chocolate reduced the chances of miscarriage by a modest 20%.
The risk of miscarriage did not vary by social class or employment status, contrary to the findings of previous research.
The results confirmed that older women and those with a history of fertility problems have a higher chance of miscarriage.
Women who had previously had abortions were more likely to miscarry, contrary to some previous research, which found no such link. Some scientists speculate that abortions might raise the risk of infections that could complicate future pregnancies.
Journal reference: BJOG (DOI: 10.1111/j.1471-0528.2006.01193.x)