More likely that older IVF mothers will suffer a pregnancy loss

It is a widely known that, as women age, it becomes more difficult for them to become pregnant.  In a study from the Weill Medical College of Cornell University, researchers documented that it is also increasingly more likely that older IVF mothers will suffer a pregnancy loss, most often due to cytogenetic abnormalities of the fetus.

In a retrospective analysis of 2,014 consecutive IVF pregnancies between October 1991 and June 1996, researchers determined that the chance of pregnancy loss for IVF patients after documentation of fetal heartbeat was slightly more than 10% overall. But the rates of miscarriage increased significantly with maternal age:  patients under 30 had a 5.3% chance of miscarrying, while the rates rose to 7.6% for those 30-34, 12.8% for those 35-39, and 22.2% for mothers 40 and older. 

Of the 233 pregnancy losses in the study group, 74 were analyzed for chromosomal defects. Three of these tests were inconclusive, 19 were normal, and 52 revealed cytogenetic defects.  For women age 40 and above, 82% of pregnancy losses were associated with chromosomally abnormal fetuses compared to 65% of losses in women under 40.

Patients who were carrying only one fetus were at increased risk of pregnancy loss (losing the entire pregnancy) than patients with multiple gestations.  The researchers noted that patients with a singleton pregnancy were, on the whole, older than those carrying multiples.  More than 25% of patients 40 and older who had a viable singleton at seven weeks failed to deliver a liveborn infant. 

The study also demonstrated that pregnancies with multiples are more likely to deliver at least one liveborn infant when compared to age-matched singleton pregnancies.  A significant rate of natural fetal loss was shown with 55% of women having three fetal heartbeats at seven weeks delivering triplets, while 34% delivered twins, and 6.5% delivered a single baby.

“This study comes at a good time as the ART community continues to refine practices to minimize the incidence and dangers of multiple births,” remarked Marian Damewood, MD, President of ASRM.  “It points out that a single approach will not work for all patients. The needs and prognoses of our older patients are different in many respects from those of our younger patients and, as the authors suggest, when we are counseling them, we need to carefully consider the number of embryos to be transferred as well as  the impact of fetal reductions on older women.”

(Spandorfer et al, Relationship between maternal age and aneuploidy in in vitro fertilization pregnancy loss, Fertility and Sterility, Vol.81, No.5, May 2004.)