Different risk factors for adverse outcomes in singleton, twin pregnancies

Key takeaways:

• Twin pregnancies had increased risks for stillbirth, neonatal ICU and preterm birth with monochorionicity.
• Advanced maternal age raised risks for mortality, neonatal ICU and preterm birth in twin pregnancies.

Risk factors for adverse pregnancy outcomes differ between singleton and twin pregnancies, according to a review published in The Journal of Maternal-Fetal & Neonatal Medicine.

“Although preliminary evidence suggests that causes of adverse outcomes may differ between twin pregnancies compared to singleton pregnancies, guidelines for optimizing outcomes in twin pregnancies are often based on evidence extrapolated from singletons,” Maya Whittaker, MBBS, obstetrics and gynecology academic and clinical fellow at Saint Mary’s Hospital at Manchester University NHS Foundation Trust and the division of developmental biology and medicine at the School of Medical Sciences in the Maternal and Fetal Health Research Centre at the University of Manchester, U.K., and colleagues wrote. “To prevent adverse outcomes, targeted evidence is needed to provide tailored care exclusively for twin pregnancies.”

Whittaker and colleagues conducted a review evaluating pregnancy risks associated with chorionicity, advanced maternal age, BMI, socioeconomic and ethnic inequalities, maternal smoking, use of assisted reproductive technologies, maternal perception of fetal movement and maternal comorbidities. The authors assessed adverse outcomes reported, including preterm birth, admission to the NICU, stillbirth and neonatal mortality.

The authors observed increased risks for stillbirth (adjusted OR = 1.81; 95% CI, 1.13-2.82), NICU admission (aOR = 1.41; 95% CI, 1.12-1.78) and preterm birth (aOR = 1.47; 95% CI, 1.17-1.86) with monochorionicity in twin pregnancies. In addition, researchers noted that advanced maternal age makes twin pregnancies more likely to have higher risks for perinatal or neonatal mortality (RR = 5.76; 95% CI, 1.11-29.7), admission to the NICU (RR = 1.78; 95% CI, 1.21-2.64) and preterm birth (RR = 2.27; 95% CI, 1.09-5.8) compared with singleton pregnancies.

However, in twin pregnancies, there was a lower impact of BMI, socioeconomic inequalities, smoking, assisted reproductive technologies and hypertensive disorders of pregnancy on adverse outcomes compared with singleton pregnancies. The researchers noted that this might be explained by the higher risk for adverse outcomes at baseline in twin pregnancies.

Use of assisted reproductive technologies and gestational diabetes both appeared to be protective against perinatal mortality in twin pregnancies despite being risk factors for adverse outcomes in singleton pregnancies.

“Our findings highlight the need for further studies in twin pregnancies to identify modifiable risk factors for adverse outcomes in twin pregnancies. Such studies must be adjusted for chorionicity to achieve meaningful outcomes,” the researchers wrote. “The resulting data would facilitate more tailored guidance for twin pregnancies, contribute to improved antenatal care and inform wider public health strategies.”