Definition

Plurality 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.

Numerator

Number of live births which were part of a multiple pregnancy (twin, triplet, etc.)

Denominator

Total number of live births

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 were triplets in 2021 is less than one-third of what it was in 1998 (2.8% and 10.1%, respectively). Among New Jersey mothers, there were 3,013 live births that were twins and 88 that were triplets in 2021.

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 Practices

The 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^]

Data Notes

Each 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.

The proportion of multiple births that are quadruplets and quintuplets is so small that it is barely visible on the pie graph.

Data Notes

Each 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.

Data Source

Birth Certificate Database, Office of Vital Statistics and Registry, New Jersey Department of Health

Older mothers have a higher spontaneous (i.e., without the use of fertility therapies) multiple birth rate. However, older maternal age accounts for only about one-third of the total rise in the multiple birth rate over time. [1,4]

Data Notes

Each 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.

Data Source

Birth Certificate Database, Office of Vital Statistics and Registry, New Jersey Department of Health

Data Notes

Each 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.   Data for White, Black, and Asian do not include Hispanics. Hispanic ethnicity includes persons of any race.

Data Source

Birth Certificate Database, Office of Vital Statistics and Registry, New Jersey Department of Health

Data Notes

Each 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.

Data Source

Birth Certificate Database, Office of Vital Statistics and Registry, New Jersey Department of Health

References and Community Resources

1. ACOG Practice Bulletin No. 231: [https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2021/06/multifetal-gestations-twin-triplet-and-higher-order-multifetal-pregnancies Multifetal Gestations Twin Triplet and Higher-Order Multifetal Pregnancies]. June 2021. 2. NJ P.L.2001, c.236: [http://www.njleg.state.nj.us/2000/Bills/PL01/236_.HTM] 3. ACOG Committee Opinion No. 719: [https://www.acog.org/clinical/clinical-guidance/committee-opinion/articles/2017/09/multifetal-pregnancy-reduction Opinion on Multifetal Pregnancy Reduction]. Sept 2017. 4. Martin JA, Hamilton BE, Osterman MJK. [https://www.cdc.gov/nchs/products/databriefs/db80.htm Three decades of twin births in the United States, 1980-2009]. NCHS data brief, no 80. Hyattsville, MD: National Center for Health Statistics. 2012. National Center for Health Statistics Multiple Births Fast Stats: [https://www.cdc.gov/nchs/fastats/multiple.htm]