Pregnancy complication rates seem to be higher in pregnancies that occurred as a result of in vitro fertilization cycles. Many theories have been put forth as to the underlying reason for the higher complication rates.

At a presentation at the 2007 American Society for Reproductive Medicine Meeting in Washington, D.C., researchers utilized the U.S. National in vitro fertilization database to determine whether pregnancies in which there was initially a multiple pregnancy but then delivered as a singleton were associated with a higher rate of pregnancy complications compared to a group of pregnancies that started and ended as a singleton pregnancy.

A total of 23,615 pregnancies were studied. The pregnancies were classified according to whether early ultrasound documented one, two or three or more fetal heartbeats. The researchers found that when an early fetal loss occurred, the resultant singleton pregnancies had a higher rate of preterm deliveries, low birth rate and low birthweight for age.

These findings could help explain why in vitro fertilization pregnancies appear to have a higher rate of some pregnancy complications.