Abstract

OBJECTIVES: The main aim of this study was to investigate the relationship between weight discordance and neonatal morbidity in twin pregnancies progressing beyond 34 weeks of gestation. The secondary aim was to determine the predictive accuracy of different weight discordant cut-offs in predicting neonatal morbidity in twin pregnancies. METHODS: This was a retrospective multicentre cohort study of all twin pregnancies booked for antenatal care in four hospitals in the Southwest Thames region of London Obstetric Research Collaborative (STORK) over a period of ten years. The ultrasound data were obtained by a computerized search of each hospital's obstetric ultrasound computer database, while the outcome details were obtained from the computerized maternity and neonatal records. The primary outcome was the incidence of composite neonatal morbidity in twin pregnancies with birthweight discordance. Logistic regression was used to identify and adjust for potential confounders, while the receiver operating characteristic curve was used to determine the predictive accuracy. RESULTS: Nine hundred and thirty-nine twin pregnancies (760 Dichorionic, 179 Monochorionic) were included. The gestation at birth and birthweight decile were significantly lower in the pregnancies complicated by neonatal morbidity compared to those which were not (p<0.001 for both). At multivariable logistic regression, gestation at birth (p<0.001), birthweight decile (p=0.029), birthweight discordance (p=0.019) but not chorionicity (p=0.477) or the presence of at least one small for gestational age twin (p=0.245), were independently associated with the risk of neonatal morbidity. There was a progressive increase in the risk of neonatal morbidity with increasing birthweight discordance. Despite this association, birthweight discordance showed an overall poor predictive accuracy in detecting neonatal morbidity, with an AUC of 0.58 (95% CI 0.53-0.63) with an optimal cut-off of 17.6%, showing a sensitivity and a specificity of 35.2% (95% CI 27.8-43.2) and 83.2% (95% CI 80.0-85.8), respectively. CONCLUSION: Inter-twin birthweight discordance is independently associated with the risk of neonatal morbidity in twins born after 34 weeks' gestation, irrespective of the chorionicity or the diagnosis of SGA in either twin. However, its predictive accuracy for neonatal morbidity is poor.