• Author
    Tra-Mi Bao
  • Discovery PI

    Ilina Pluym, MD

  • Project Co-Author

    Prisca C. Diala, MD

  • Abstract Title

    Adverse obstetric and neonatal outcomes in dichorionic twins: Does Zygosity Play a Role?

  • Discovery AOC Petal or Dual Degree Program

    Basic, Clinical, & Translational Research

  • Abstract

    Background:

    Twin gestations, comprising approximately 3% of live births in the United States, are associated with increased maternal and neonatal morbidity and mortality, with risk stratification typically based on chorionicity. However, the independent contribution of zygosity – particularly among dichorionic twin pregnancies – remains unclear.

    Study Design:

    We conducted a retrospective cohort study of dichorionic twin pregnancies delivered after 24-week gestation at two academic affiliated urban medical centers between 2016 and 2024. Zygosity was determined by noninvasive prenatal testing (NIPT), neonatal sex at birth, or inferred from in vitro fertilization (IVF) frozen embryo transfer records. The primary outcome was preterm delivery rate in monozygotic (MZ) versus dizygotic (DZ) twins; the secondary outcome was composite neonatal morbidity. Multivariable logistic regression identified predictors of preterm delivery and neonatal morbidity after adjusting for demographic and clinical factors.

    Results:

    Among 265 dichorionic twin pregnancies, 94% were DZ (n=249) and 6% MZ (n=16). Maternal and fetal characteristics–including age, body mass index (BMI), IVF status, hypertensive disorders (HD), gestational diabetes, fetal growth restriction (FGR), and anomalies–were similar between groups. Preterm delivery occurred in 51% of DZ and 44% of MZ pregnancies (p=0.40). A neonatal morbidity event occurred in 43% of DZ and 34% of MZ pregnancies (p=0.36). Severe FGR (aOR 5.09, 95% CI 1.54–16.83) and HD (aOR 1.70, 95% CI 1.16–2.51) were independent predictors of preterm delivery, while increased parity was protective (aOR 0.51, 95% CI 0.27–0.95). Predictors of neonatal morbidity were small for gestational age (aOR 1.77, 95% CI 1.01–3.11), IVF conception (aOR 1.72, 95% CI 1.04–2.84), HD (aOR 1.73, 95% CI 1.09–2.74), and preterm delivery (aOR 22.24, 95% CI 13.01–38.03).

    Conclusion:

    Zygosity did not significantly impact obstetric or neonatal outcomes in dichorionic twin pregnancies. Adverse outcomes were primarily driven by pregnancy-related factors, such as FGR and HD. These findings suggest that adverse outcomes in dichorionic twin pregnancies are mainly driven by clinical factors, rather than genetic twinning status.

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