Multiple Births

Introduction

Twins, triplets, and higher-order multiples always attract attention. From ancient mythology to popular television programs and current bestsellers, multiples capture the imagination of people regardless of culture or life situation. Despite all this attention from the lay press, however, medical literature has focused relatively little on issues surrounding multiples. Few articles are written, and few studies are performed that examine what makes multiples different and what parents of singletons can learn from twins, triplets, or more multiple births.

Epidemiology

Currently in America, approximately 1 in every 250 births is a multiple: twins, triplets, or higher-order multiples. In 2003, for example, 128,000 twins and 7,600 triplets and higher-order multiples were born compared with approximately 4,089,000 total live births that year, an average of nearly 31.5 twins and 1.9 triplets/higher-order multiples born per 1,000 live births. These figures represent an increase of 65% in the incidence of multiple gestations and deliveries since 1980.

Many factors influence this increase in multiple pregnancies. The principal causes, however, are advancing maternal age and infertility treatments. As women get older, their chance of having multiples doubles. Women between 20 and 24 years of age have twins at the rate of approximately 22.4 per 1,000 live births, whereas women between 40 and 44 years have twins at the rate of 51.3 per 1,000 births. Women also are having children later; in 2003, for example, the birth rate for women between 40 and 44 years of age was approximately 8.7 births per 1,000 women compared with 3.9 births per 1,000 women in 1980.

Infertility treatments also increase the rates of multiple gestations and deliveries. A study by Bardis and associates (1) demonstrated a greater than 10-fold rise in the rate of twinning following fertility treatments. Their data showed a 13.5% multiple pregnancy rate following fertility treatments compared with 1.2% …