What are supertwins? Beyond twins, supertwins are triplets and other higher order multiple births. The babies may be identical or fraternal or a combination of the two. The incidence of spontaneously-occuring triplets 1 in 7,000; quadruplets 1 in 571,000; and quintuplets 1 in 47,000,000.
A woman carrying more than one baby is automatically considered to have a high risk pregnancy, and is at increased risk for pre-term labor. The Journal of the American Medical Association reported in 1996 that the optimum gestation for multiple births was 37 to 38 weeks, though with more than two, birth is likely to occur much earlier.
The National Center for Health Statistics reports that there has been a remarkable rise in the number of supertwin births over the past two decades. Up from 1,034 births in 1971 to 4,973 for 1995, the increase in higher order multiple births (triplets, quadruplets, and quintuplets) reflect the rising number of births to women in their thirties, who are more likely to have a multiple birth, and the use of fertility-enhancing drugs and techniques. Yet, babies born in triplet and other higher order multiple deliveries arrive smaller and earlier than single births and are at greater risk of infant death and lifelong health problems.
The number of live births in triplet deliveries tripled between 1980 (1,337) and 1995 and quadrupled since 1971. Over the last decade, increases in the number of triplet births averaged 11 percent a year. The ratio of triplet births per 100,000 births rose 272 percent between 1980 and 1995. In 1995 the 4,973 triplet and other higher order multiple births included 4,551 triplets, 365 quadruplets, and 57 quintuplets and greater births.
Triplet births are at much greater risk than single births. Infant mortality rates are 12 times higher for these births than for single births. The average birth weight of a triplet newborn is only half that of a single birth and the period of gestation is, on average, 7 weeks shorter. For 1995, 92 percent of triplets were born preterm compared with just over 10 percent of births in single deliveries.
The major factor underlying the increase in triplet births appears to be the use of ovulation-enhancing (fertility) drugs and assisted reproductive techniques, such as in vitro fertilization. Only one-third of this increase reflects the shift in maternal age, with more babies born to mothers in their thirties. Overall, increases in triplet births were most pronounced among married, college-educated mothers 30 years of age and over.