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223: Fetal growth restriction is associated with different patterns of placental abnormalities in twin and singleton pregnancies

      Objective

      The rate of fetal growth restriction (FGR) is higher in twin compared with singleton pregnancies. However, the mechanisms underlying FGR may differ between twins and singletons. Our aim was to compare the placental findings between twin and singleton pregnancies complicated by FGR.

      Study Design

      This was a retrospective cohort study of all singleton and twin SGA (birth weight <10th%) newborns delivered in a single tertiary referral center between 2001-2015. SGA was diagnosed in twins and singletons using the recently published NICHD twins- and singletons-based growth charts, respectively. Placental abnormalities were compared between twins and singletons and were classified into maternal vascular malperfusion, loss of integrity, fetal vascular malperfusion, and chronic inflammation.

      Results

      1) A total of 1,282 SGA newborns were identified during the study period, of whom 365 (28.5%) were twins. 2) The rate of any placental pathology was lower for SGA twins compared with SGA singletons (38.1% vs 67.8% p<0.001), mainly due to a lower rate of maternal malperfusion lesions (4.1% vs. 42.1% p<0.001). 3) On multivariable regression analysis, SGA in twins was associated with lower odds of any placental abnormality (OR 0.29, 95%-CI 0.23-0.38) and maternal vascular malperfusion (OR 0.06, 95%-CI 0.04-0.10) (TABLE). 4) Plurality was not associated with the risk of fetal vascular malperfusion lesions and chronic villitis (TABLE).

      Conclusion

      SGA in twin pregnancies is less likely to be associated with maternal vascular malperfusion lesions compared with SGA in singletons. These findings may imply that the mechanisms underlying fetal growth FGR in twins differ from those in singleton pregnancies.
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