In a study conducted at Columbia University's Mailman School of Public Health and the New York Psychiatric Institute researchers found that increasing paternal age is significantly associated with increased rates of spontaneous abortion, a pregnancy loss occurring before twenty weeks of gestation.
Results indicate that as the male partner ages there is a steady increase in rate of miscarriage.
Women with partners aged 35 or older had nearly three times as many miscarriages as compared with women conceiving with men younger than 25 years of age. This finding is independent of the woman's age and not explained by other factors such as diabetes, smoking, or previous spontaneous abortions, and adds to the growing realization of the importance of paternal characteristics for successful reproductive outcome.
"There has been a tremendous amount of research on women, and how their characteristics affect pregnancy outcomes. Of course, women's importance and centrality to pregnancy cannot be overstated. However, scientists seem to have forgotten that men are equal partners in reproduction, and their influence should be studied to the same degree. Our group has focused on men's influence on the health of their offspring, and we have made some fascinating discoveries," said Karine Kleinhaus, MD, MPH currently in Columbia's Department of Psychiatry and first author of the study. "This study shows how a man's age affects the likelihood of miscarriage."
Earlier research by the Columbia scientists showed that older men's wives suffer from preeclampsia, while the offspring of older men are more likely to get schizophrenia. "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," observes Dr. Klienhaus. In fact, 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.
The international team of scientists involved in the study used a large historical data set containing information on many characteristics of mothers and fathers that might contribute to spontaneous abortion. The researchers analyzed data from the ante-natal or post-partum interviews of 13,865 women. This data was recorded in the Jerusalem Perinatal Study, a population-based cohort derived from 92,408 births in Jerusalem in 1964-1976.
Accordingly, the study, which focused exclusively on spontaneous abortion as the outcome, has as one of its strengths its large sample size and its extensive data, which permit consideration of important potential confounders not included together in other analyses. These include variables such as maternal diabetes, parity, history of prior spontaneous and induced abortions, and history of maternal smoking, and socioeconomic status.
The cohort used for this study is unique, with immigrants from many origins, including Iran, Iraq, Afghanistan and countries of North Africa, as well as Central and Eastern Europe. "This broad mix of backgrounds makes our study findings more generalizable," observed Susan Harlap, MD, professor of clinical epidemiology in the Mailman School of Public Health's Department of Epidemiology, and the leader of this research team. "While several previous studies suggested that father's age might contribute to miscarriage, they failed to clarify whether there is a cut-off age or a progressive trend over the whole range of ages."
The study findings generate strong support for the association of increasing paternal age with increasing rates of spontaneous abortion, and are corroborated by other published studies. "Advanced paternal age may result in only a slight increase in the chance of spontaneous abortion for a specific couple. Nevertheless, as child bearing is increasingly delayed in Western societies, this study provides important information for people who are planning their families," said Dr. Kleinhaus. "The study also adds to a growing understanding of how men's age, health, and occupations can affect their partner's pregnancies and the offspring's future development."