The risk of a pregnancy ending in miscarriage might increase in tandem with the father's age. Older women are known to have a higher risk of miscarriage than younger ones, but the effect of man's age on pregnancy is less clear. Researchers from the French National Institute for Health and Medical Research (INSERM) in Le Kremlin-Bicetre conducted a study and followed more than 5,100 pregnant women from the first trimester onward. Their findings strengthen the evidence of a connection between a father's age and miscarriage risk. The researchers followed 5,121 California women from the first trimester until they gave birth or the pregnancy ended. Overall, 491 women had a miscarriage after the sixth week of pregnancy. They found that, regardless of the woman's age, a couple's risk of miscarriage grew steadily as the man's age increased from 20 to 50. Overall, miscarriage risk was 27 percent greater if the man was older than 35 than if he was younger. The findings suggest that the influence of paternal age on the risk of spontaneous abortion is very likely to exist. It's believed that as men age, they tend to produce a greater number of sperm with chromosomal abnormalities. Chromosome defects in the fetus are responsible for a large portion of miscarriages particularly in the first trimester. So it may be through transmission of genetic anomalies from sperm to embryo that a father's age affects miscarriage. Like people, sperms also get older. Initially, the researchers found that a 40-year-old woman had more than three times the risk of miscarriage as a 25-year-old woman did. When they factored in the man's age, the risk associated with older maternal age dipped. Part of the effect formerly attributed to maternal age was actually due to paternal age. It was found that miscarriage risk steadily increased, as men grew older doubling between the ages of 20 and 50. For women, the risk increased roughly five-fold between the ages of 20 and 45.
American Journal of Epidemiology,
May 2005