Q&A's about multiple births

DR. MOORE practices general pediatrics with Carilion Pediatric Medicine in Roanoke, Va., and is the father of 2-year-old fraternal twin daughters. He has nothing to disclose in regard to affiliations with, or financial interest in, any organization that may have an interest in any part of this article.

This pop culture attention is not matched by intensive medical research, however. Relatively little is written about twins and higher-order multiples in peer-reviewed journals. Doctors have rarely focused on the particular medical and psychological needs of twins and their parents. Twin lore is plentiful, but medical information is not. This Q and A identifies the questions that parents of twins ask most frequently and gives you the scientific basis you need to deal with their concerns. The parent handout can also be helpful.

A You're not imagining it. The rate of multiple gestation and delivery is at record high levels worldwide. According to 2003 data from the Centers for Disease Control and Prevention (CDC), one in every 250 American deliveries is a multiple birth. That means, on average, one new set of multiple infants in every pediatric practice that year, assuming an average of 125 new babies per year for a typical thriving pediatric practice. For every 1,000 live births in 2003, 32 sets of twins and two sets of triplets were delivered-an increase of roughly 65% in the frequency of multiple deliveries since 1980.¹

Q "What's going on? Are fertility treatments to blame?"

A Yes, that's the most important reason. A recent British study of babies born during a single week in 2003 found that women who had had fertility treatments were more than 10 times as likely to have a twin pregnancy.² In that study, 13% percent of the pregnancies resulting from infertility treatments were multiple, compared to approximately 1% of the pregnancies in women who had conceived spontaneously. In the US, 18% of the multiples born in 2003 were conceived via fertility treatments.³

In-vitro fertilization (IVF) appears to carry an especially elevated risk of multiple gestation. In another 2003 British study, the multiple pregnancy rate for women who underwent IVF was 26%, roughly double the rate for other forms of fertility treatments surveyed.⁴ The reason for the dramatic difference in twinning seen from IVF is the practice of multiple-embryo transfer. Reproductive endocrinologists have historically transferred several fertilized embryos with every IVF cycle. Some physicians are beginning to question this strategy, however, asking whether the risks of multiple gestation may not outweigh the benefits from increased successes per cycle. If the practice becomes uncommon, the effect on the rate of multiple pregnancies will become known over the next several years. In general, it seems likely we shall see a reduction in the rates of twinning from IVF in the future.