We read with interest the article by Dodd et al.1 They randomised a total of 235 women carrying twin pregnancies either to have elective birth at 37 weeks or standard care (planned birth from 38 weeks). They argue on the basis of their findings that in uncomplicated twin pregnancy, elective birth at 37 weeks of gestation was associated with a significant reduction in risk of serious adverse outcome for the infant.
We applaud the authors for undertaking this important and challenging study, but wish to raise some points for consideration. We note that there is no mention of the method of gestational age assessment in the twin pregnancies recruited to the study. Accurate dating in early pregnancy is fundamental not only in routine clinical management of twin pregnancies, but also in determining the applicability of their data to the general population. Fairly robust evidence is now available that twin pregnancies can be accurately dated using crown–rump length between 11 and 14 weeks of gestation and by head circumference thereafter.2,3 The authors also failed to analyse the data according to the chorionicity of the twins.4 Recent, large cohort studies have demonstrated significantly higher stillbirth rates near term even in apparently low-risk monochorionic twin pregnancies.5 The latter may well justify a differential policy for the timing of delivery in monochorionic versus dichorionic twin pregnancies.5
Probably the most notable finding is that the majority of events labelled an ‘adverse outcome’ were birthweight less than the third centile (24/29 in standard care versus 7/11 in elective birth). Given that the latter is a relatively common finding in twin pregnancies and less commonly associated with real morbidity than in singletons, would the exclusion of this outcome variable leave the study adequately powered to truly evaluate the appropriate timing of birth in twin pregnancy?