The use of assisted reproductive technology to help infertile couples conceive is steadily increasing. The Centers for Disease Control and Prevention (CDC) collects nationwide data from fertility clinics each year on success rates for achieving pregnancy and live births. Data are also tracked for the incidence of multifetal gestations, one of the chief complications of assisted reproductive methods. Pressure has mounted to decrease the number of embryos transferred in pregnancy attempts, because multifetal gestations are associated with serious health risks for mothers and children. Jain and associates analyzed national data to determine trends in pregnancy success rates and the incidence of multifetal gestations.

CDC data from fertility clinics from the years 1995 to 2001 were used for the study. The authors limited their analysis to fresh embryos from a woman's own eggs, which is the method used by most infertile couples. Data were stratified according to four maternal age groups (less than 35 years, 35 to 37 years of age, 38 to 40 years of age, and more than 40 years). Despite federal laws requiring the reporting of success rates, 5 to 9 percent of fertility clinics failed to provide statistics in any given year of the study. A successful pregnancy was defined as one or more gestational sacs seen in the uterus by first trimester ultrasound examination. Live birth data were obtained from National Vital Statistics Reports.

The number of infertility clinics and fresh-embryo transfer attempts steadily increased nationwide from 1995 to 2001. The rate of achieving pregnancy was higher than the rate of live births, and both numbers increased for all age groups over the course of the study. The average number of fresh embryos transferred in each attempt declined in later years, with no deleterious effect on the rate of live births. While rates of twin deliveries did not decrease during the study, the incidence of triplet and higher number multifetal gestations stopped its steady climb and stabilized after 1998, according to national data.

The authors conclude that pregnancy and live-birth success rates for assisted reproductive technology improved steadily from 1995 to 2001, and the number of triplets and higher number multifetal gestations leveled off in recent years.

editor's note: Family physicians often are involved when infertile couples begin the decision process regarding the use of assisted reproductive technology. While success rates and the risk of multifetal gestation will, of course, vary depending on individual circumstances, national data such as these do help couples to realistically consider their overall odds before embarking on a process that involves considerable emotional and financial risks. —b.z.