OC23.02: Postnatal catch‐up growth in discordant twins within 2 years according to the obstetric characteristics

This study was performed to investigate the postnatal growth of discordant twins and the predictive factors associated with catch-up growth of smaller twins. Retrospective cohort study was conducted in a tertiary center. We enrolled twin pairs with discordance excluding cases with unknown chorionicity, neonatal death, major anomalies, and twin–twin transfusion syndrome. Discordance was defined as 20% or more difference of birthweight. Successful postnatal catch-up growth of smaller twin was defined as less than 10% of weight difference. Growth data were collected from medical records up to the age of 2 years. Of 1,422 twin pairs, 200 twin pairs met the inclusion criteria (40 pairs, monochorionic; 160 pairs, dichorionic). Discordances were reduced or reversed postnatally in 96.0% (192/200) of twins compared with their discordances at birth. Discordances were maintained or aggravated only in 4% of twins postnatally, and all of them were dichorionic twins (7 pairs, dizygotic; 1 pair, unknown zygocity). Of 135 twin pairs with follow up after neonatal period, smaller twins achieved successful postnatal catch-up growth in almost half of twin pairs (46.7%). Logistic regression analysis demonstrated that 25% or more birthweight discordance (OR, 3.41; 95% CI, 1.46-8.00; P = 0.005) and preterm delivery before 32 weeks of gestation (OR, 6.25; 95% CI, 1.51-25.88; P = 0.012) were associated with failure of postnatal catch-up growth of smaller twins. Discordance was reduced postnatally in most of discordant twin pairs. It suggests that certain intrauterine factors may affect fetal growth in multifetal pregnancy. However, discordance seems to be maintained postnatally in some dizygotic twins who have different growth potential. Marked discordance at birth (≥25%) and preterm delivery (<32weeks) may be risk factors for postnatal catch-up growth of smaller twins.