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30: New thresholds for significant intratwin growth discordance: results of the prospective multicenter ESPRiT study

      Objective

      To determine the level of intratwin birthweight (BW) discordance at which perinatal mortality and severe morbidity increase in monochorionic and dichorionic twin pregnancy.

      Study Design

      This prospective multicenter study included 1028 unselected twin pairs recruited over a 2-year period in one country. All participants underwent 2-weekly intensive sonographic surveillance by a team of highly-trained sonographers, from 24 weeks' gestation, with surveillance of monochorionic (MC) twins 2-weekly from 16 weeks. All perinatal outcomes were entered onto a central consolidated database. Analysis using Cox proportional hazards was conducted to compare perinatal mortality and a composite measure of perinatal morbidity (respiratory distress syndrome/ hypoxic ischemic encephalopathy/ periventricular leukomalacia /necrotising enterocolitis/ sepsis) at different degrees of birthweight discordance, with adjustment for chorionicity and gestational age at delivery.

      Results

      Complete study data was available for 1001 women. Chorionicity was assigned as mono-or dichorionic (DC) in 19% (192/1001) and 81% (809/1001) of pregnancies, respectively. Pre-viability single or dual fetal demise was identified in 24 pairs, such that perinatal outcome was recorded for 100% (977) patients who continued the study with both fetuses alive beyond 24 weeks' gestation. Mean BW discordance was 13.2% (range 0.1% to 53%) and 11.4% (range 0% to 58%) for MC and DC twin pairs, respectively. Adjusting for gestational age at delivery, perinatal mortality, individual and composite perinatal morbidity were all seen to increase in association with intratwin birthweight discordance in excess of 14% for monochorionic pairs (Hazard ratio=2.04, p=0.006) and 17% for dichorionic pairs (Hazard ratio=2.08, p <0.0001).

      Conclusions

      The degree of intratwin birthweight discordance which serves as an independent predictor of perinatal mortality or severe morbidity is 14% for monochorionic pairs and 17% for dichorionic twins. This threshold for significant discordance is considerably lower than that defined by retrospective series as pathologic.
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      Figure 1Kaplan-Meier morbidity-free survival curves