Male Biological Clock

Researchers have long known that a woman's fertility decreases with age, but now a new study has found that the rate of pregnancy is lowered and the number of miscarriages increases when the father is over the age of 35. This is according to Dr. Stéphanie Belloc, of the Eylau Centre for Assisted Reproduction, Paris, France who detailed the results of the study at the 24th annual conference of the European Society of Human Reproduction and Embryology. Belloc says that this study is the first to link paternal aging with reproductive failure.

Dr. Belloc and colleagues obtained their results by following 21239 couples who had undergone intrauterine insemination (IUI). Participants in the study included 12236 couples who had been treated at the Eylau Centre between January of 2002 and December of 2006. In all of the cases, the husband's sperm was employed for the IUI procedure. In a great majority of the cases, IUI was performed due to the male partner's infertility.

Necessary Step

A necessary step in the IUI procedure is sperm washing, in which the semen is spun in a centrifuge to separate sperm out of the seminal fluid. The resulting sample is then inserted straight into the uterus. Washing the sperm prevents cramping and subsequent miscarriage due to the high level of prostaglandins in natural seminal fluid.

For the purposes of this study, the sperm of each male partner was examined for sperm count, motility, and for the percentage of live sperm (morphology). The rates for pregnancy, miscarriage, and delivery were also recorded. The high level of detail recorded by the researchers allowed for the separation of male versus female factors in relation to the resulting pregnancies.

As expected, maternal aging caused a decrease in the rate of pregnancy. Women over 35 years of age got pregnant through IUI at a rate of 8.9% as compared to the 14.5% of younger women in the study. Miscarriages were also higher in the upper maternal age range.

Tick Tock

"But we also found that the age of the father was important in pregnancy rates -- men over 35 had a negative effect," says Dr. Belloc. "And, perhaps more surprisingly, miscarriage rates increased where the father was over 35."

While there have been several studies demonstrating the decline in sperm quality and counts as men age, until now, there has been no statistical proof that paternal age has direct bearing on a couple's ability to conceive a child.

Though this study was performed on a large number of participants, the researchers would like to add more couples to their study within the next several years in order to bear further proof of the male biological clock as a reason for infertility. "This research has important implications for couples wanting to start a family," says Dr. Belloc, "and we need to research it in as large a group as possible."


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