DefinitionPlurality is the number of all live births and pregnancy losses (miscarriages, ectopic pregnancies, fetal deaths, selective reductions) in a pregnancy. Multiple births are twins, triplets, quadruplets, and higher order births.
NumeratorNumber of live births which were part of a multiple pregnancy (twin, triplet, etc.)
DenominatorTotal number of live births
Data Interpretation IssuesEach infant in a multiple birth is counted separately, so, for example, three triplets refers to three live born infants, not three sets of triplets and not necessarily three infants from the same triplet set. If, for example, a mother has a triplet pregnancy and one child is not live born, the two live born infants are each still considered to be one of a set of triplets, not twins.
Why Is This Important?There is a high risk of adverse outcome for multiple births.[https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2021/06/multifetal-gestations-twin-triplet-and-higher-order-multifetal-pregnancies ^1^] The outcomes are addressed in the respective indicator profiles.
How Are We Doing?Both the number and rate of multiple births generally increased through the 1990s and 2000s before beginning to decline after 2011.
The vast majority (97%) of multiple births are twins. The number of triplets peaked in 1998 (at 467) and the proportion of multiples that are triplets is now less than one-third of what it was that year (2.9% and 10.1%, respectively).
How Do We Compare With the U.S.?The multiple birth rate in New Jersey had been higher than that of the nation as a whole from 1992-2018. This is thought to be due, in part, to assisted reproductive technology (ART) and the proximity of such services throughout the state, as well as the affluence of some parts of New Jersey compared to other parts of the country. Since 2001, state law has required health insurers to provide coverage for medically necessary expenses incurred in diagnosis and treatment of infertility, including ART.[http://www.njleg.state.nj.us/2000/Bills/PL01/236_.HTM ^2^]
Evidence-based PracticesThe American College of Obstetricians and Gynecologists' (ACOG) Committee on Ethics published an Opinion report in 2017 advising obstetrician-gynecologists (Ob/Gyns) to be knowledgeable about the medical risks of multifetal pregnancy, the potential medical benefits of multifetal pregnancy reduction, and the complex ethical issues inherent in decisions regarding multifetal pregnancy reduction. Multifetal pregnancies should be prevented whenever possible. When multifetal pregnancies do occur, incorporating the ethical framework presented in the Committee Opinion will help Ob/Gyns counsel and guide patients as they make decisions regarding continuing or reducing their multifetal pregnancies.[https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/09/multifetal-pregnancy-reduction ^3^]