Aging Males Contribute to Miscarriage Rate

NEW YORK, Aug. 4 -- Paternal age is a significant risk factor for miscarriage, according a case control study of almost 14,000 pregnancies. It showed that men start to go downhill after 35.

Women with partners ages 35 or older had nearly a threefold increase in spontaneous abortions compared with women whose partners were younger than 25, wrote Karine Kleinhaus, M.D., M.P.H., of Columbia's Mailman School of Public Health, and colleagues, in the Aug. 1 issue of Obstetrics and Gynecology.

The risk, while small, begins to increase as fathers reach age 35, wrote Dr. Kleinhaus and colleagues at New York Psychiatric Institute and the Braun School of Public Health and Community Medicine at Hebrew University-Hadassah in Jerusalem.

When the father was 40 or older, the odds ratio for spontaneous abortion was 1.6 (95% CI 1.2-2.0, P=0.003) compared with the rate when fathers were younger than 25 (OR: 0.59; 95% CI 0.45-0.76, P<0.0001).

The increased risk was independent of maternal age and was not confounded by diabetes, smoking, parity, or previous spontaneous abortions.

Although paternal age may only result in a "slight increase" in risk of miscarriage for a specific couple, the authors cautioned that since pregnancy is "increasingly delayed in Western societies, this study provides important information for people who are planning their families."

The researchers conducted a case control study of 13,865 women enrolled in the Jerusalem Perinatal Study, a population-based cohort derived form 92,408 births from 1964 to 1976. All women were interviewed at the first antenatal visit and again during the days immediately following delivery.

The 1,506 case women all reported a history of spontaneous abortion in the pregnancy immediately preceding the interview. Cases were compared to 12,359 women who reported live births in the pregnancy preceding interview.

"This is not as surprising as it may sound at first, as it was already shown by other researchers that older men have more abnormalities in their sperm, and that their children are more susceptible to certain birth defects," said Dr. Klienhaus.

For example, the American Society for Reproductive Medicine has set an upper age limit of 40 years old for semen donors because of the increased risk of genetic abnormalities in the offspring of older fathers.

Although the study was strengthened by its large sample size, the authors noted that it was limited by its reliance on recall of prior pregnancies and the possibility that induced abortions may have been misreported as spontaneous abortions.