July 7, 2008 -- A woman's age plays a key role in her ability to get pregnant, but a landmark study now shows that dad's age may be just as important.
A study of more than 12,000 couples undergoing fertility treatments has found that pregnancy rates drop and miscarriages increase when the father is older than 40. The findings are being presented today at the 24th annual conference of the European Society of Human Reproduction and Embryology in Barcelona, Spain.
The results are believed to be the first to show that simply being an older dad has a strong effect on reproductive outcomes.
Researcher Stephanie Belloc of the Eylau Centre for Assisted Reproduction in Paris and colleagues analyzed the outcomes of more than 21,000 intrauterine inseminations (IUIs). An IUI is a type of fertility treatment in which the man's sperm is first separated (or "washed") from the seminal fluid and then inserted into the woman's uterus. The team looked at sperm quality and pregnancy, miscarriage, and delivery rates.
"We found that the age of the father was important in pregnancy rates -- men over 40 had a negative effect," Belloc says in a news release. "And, perhaps, more surprisingly, miscarriages rates increased where the father was over 40."
How a father's age influences fertility has been a matter of debate. Until now, there's been no clinical proof that simply being an older dad directly affects a couple's ability to conceive and achieve a healthy pregnancy.
"Our research proves for the first time that there is a strong paternal age-related effect on IUI outcomes, and this information should be considered by both doctors and patients in assisted reproduction programs," Belloc says.
Even though the trial involved a large number of couples, Belloc plans further studies to confirm the results. "This research has important implications for couples wanting to start a family," she says, "and we need to research it in as large a group as possible."
Belloc recommends that fertility specialists suggest in vitro fertilization [IVF] or intracytoplasmic sperm injection (ICSI) -- a technique that places sperm directly into an egg -- to couples when either partner is over age 40.
"These methods, although not in themselves a guarantee of success, may help couples where the man is older to achieve a pregnancy more quickly, and also reduce the risk of miscarriage," she says.
Belloc's results also confirmed that women over 35 have lower pregnancy rates than younger woman, and are more likely to miscarry.