BACKGROUND AND PURPOSE:

• Currently, ACOG does not specify growth rates or nomograms for fetal growth assessment in twins
• Mendez-Figueroa et al. (Amer J Perinatol, 2017) sought to determine the ability of twin-specific nomograms, compared to singleton nomograms, to detect growth abnormalities in twin pregnancies and whether abnormal growth is associated with adverse outcomes twins

METHODS:

• Secondary analysis of Maternal-Fetal Medicine Units (MFMU) twin databases from previous studies
• Inclusion criteria included
  • nonanomalous twins ≥24w0d
• Nomograms used
  • Alexander et al. (singleton data)
  • Ananth et al. (dichorionic twin data)
• SGA: birthweight ≤ 10^th percentile
• AGA: between 11^th and 89^th percentile
• LGA: ≥ 90^Th percentile
• Composite neonatal morbidity (CNM) included
  • 5-minute Apgar score < 4, respiratory distress syndrome, mechanical ventilation, intraventricular hemorrhage grade III or IV, necrotizing enterocolitis grade 2 or 3, neonatal sepsis, periventricular leukomalacia, confirmed seizure, stillbirth, or neonatal death
• Logistic regression models were adjusted for maternal race, body mass index, neonatal sex, study, and twin correlation

RESULTS:

• Using a singleton nomogram
  • More twins categorized as SGA (33% vs 4%)
  • CNM was higher in SGA compared to AGA (adjusted odds ratio [OR] 1.19; 95% CI 1.08–1.32)
  • Stillbirth rates among was higher in SGA twins compared to AGA (aOR 3.57; 95% CI 2.16–5.90)
  • Neonatal mortality rates were similar in SGA and AGA
• Using a twin-specific nomogram
  • More twins categorized as LGA (1.9% vs 0.2%)
  • Higher odds of CNM in SGA compared to AGA (aOR 1.68; 95% CI 1.23–2.29)
  • Higher odds of stillbirth in SGA compared to AGA (aOR 7.54; 95% CI 4.2–13.6)
  • Higher odds of neonatal mortality in SGA compared to AGA (aOR 4.59; 95% CI 2.76–7.63)

CONCLUSION:

• Singleton nomograms will misclassify twins that are SGA and at risk for adverse outcomes
• Unlike singletons, LGA twins did not appear to have an increased risk of adverse outcomes which may due to route of delivery and earlier gestational age at delivery
• Use of twin-specific nomograms will decrease pregnancies classified as SGA but increase identification of pregnancies at risk for adverse outcomes

Learn More – Primary Sources:

Growth among Twins: Use of Singleton versus Twin- Specific Growth Nomograms

Related ObG Topics:

Planned C-Section or Vaginal Delivery in Twins?

Preventing Preterm Birth in Twins – What works?

Do Twins or Singletons Have a Higher Rate of Preterm Mortality?