Higher Rates of Twinning Among Repeat Vs First-Time Teenage and Young Adult Mothers in the United States, 2009-2018.

STUDY OBJECTIVE

Few studies examining predictors of twinning consider younger mothers who do not use assisted reproductive technologies (ART). Higher parity is associated with greater odds of having a twin birth, but it is unclear whether this association is present among young women. We tested the hypothesis that the rates and odds of twinning would increase with parity among teenage and young adult mothers who did not use ART.

DESIGN, SETTING, AND PARTICIPANTS: We conducted a retrospective, population-based cohort study using 2009-2018 United States National Vital Statistics data on 11,383,370 (58.94% first, 41.06% repeat) births to adolescent and adult women aged 15-24 years.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Rates and odds of twinning by parity among teenage (15-19 years) and young adult (20-24 years) mothers.

RESULTS

The adjusted twin birth rate among first-time teenage mothers was 13.28 per 1000 births compared to 16.62 twins per 1,000 births among repeat teenage mothers. This difference by parity was present but smaller among mothers aged 20-24 (18.31 vs 21.44 twins per 1000 births for first-time and repeat young adult mothers, respectively).

CONCLUSION

Repeat young mothers, particularly teenage mothers, are a high-risk group in terms of infant and maternal health outcomes; their higher rate of twinning puts them at an additional risk for adverse birth outcomes. Practitioners may counsel young mothers at risk for subsequent unintended pregnancy on elevated risk of twinning.