Weight discordance and perinatal mortality in monoamniotic twin pregnancies: analysis of the MONOMONO, NorSTAMP and STORK multiple pregnancy cohorts

OBJECTIVES: To explore the risk of perinatal mortality in monochorionic monoamniotic (MCMA) twin pregnancies complicated by inter-twin birthweight (BW) discordance. METHODS: This analysis includes data on 242 MCMA twin pregnancies (484 fetuses) from three major research collaboratives on twin pregnancies (MONOMONO, STORK and NorSTAMP). The primary aim was to quantify the risk of intrauterine (IUD), neonatal (NND) and perinatal (PND) death comparing weight discordance at birth from ≥ 10% up to ≥30%. The secondary objectives were to investigate the role of fetal monitoring (inpatient vs outpatient) in modifying the risk of mortality in weight discordant pregnancies, and to explore the diagnostic accuracy of BW in predicting mortality. Logistic regression and AUC analyses were used to analyze the data. RESULTS: The risk of IUD in MCMA twin pregnancies increased significantly from an OR=2.4 (95% CI 1.1 to 5.6, p=0.050) for a ≥20% discordance to an OR=4.4 (95% CI 1.3 to 14.4, p=0.001) for a ≥30% discordance compared to lower cut-off groups. This association remained significant on logistic regression analysis. However, weight discordance had a low predictive accuracy for mortality with an AUC of 0.60 (95% CI 0.46 to 0.73), 0.52 (95% CI 0.33 to 0.724) and 0.57 (95% CI 0.45 to 0.68) for IUD, NND and PND, respectively. There was no difference in the risk of overall IUD, single IUD, double IUD, NND and PND between pregnancies managed as inpatient compared to outpatient for all levels of discordance. CONCLUSION: MCMA twin pregnancies with birthweight discordances ≥20% are at increased risk of fetal demise, signaling a need for increased levels of monitoring. Despite this, its predictive accuracy for mortality is low, thus detection of BW alone should not trigger intervention (eg: iatrogenic delivery). Finally, the current data does not demonstrate an advantage for inpatient over outpatient management in these cases. This article is protected by copyright. All rights reserved.