Growth Disorders in Twins: An Individual Participant Data Meta-Analysis of Perinatal Mortality

Abstract

In uncomplicated dichorionic (DC) and monochorionic (MC) twin pregnancies with normally grown fetuses, the optimal time of delivery is 37 and 36 weeks, respectively. The influence of growth discordance on the optimal time of birth, with or without small for gestational age (SGA, < 10th centile), is unknown. We aimed to determine the optimal timing of birth by evaluating the rates of stillbirth (SB) and neonatal death (NND) in women with DC and MC twins with different levels of growth discordance and in relation to SGA. We performed an Individual Participant Data Meta-Analysis of studies reporting rates of SB and NND in women with twin pregnancies from 34-41 weeks (PROSPERO ID: CRD42018090866). Monoamniotic twin pregnancies were excluded. The prospective risk of perinatal death was calculated as the difference between the prospective risk of SB and risk of NND per gestational week. Analyses were stratified by chorionicity, different intervals of growth discordance and presence of SGA in one or both twins. We did not analyse data about associated obstetric complications or abnormal ultrasound findings. We included 20 studies reporting on 7474 women with DC and 2281 women with MC twin pairs. For both DC and MC twins the absolute risks of SB and NND were higher when one or both twins were SGA and increased with greater levels of growth discordance. Regardless of level of growth discordance or presence of SGA, women with DC and MC twins had higher risk of SB than NND from 37 weeks onwards (Fig. 1, Fig. 2). For MC twins, the nadir was between 36-37 weeks. The nadir for perinatal mortality risk for women with DC twins with growth discordance or SGA is around 37 weeks. For MC twins this is between 36-37 weeks, favouring delivery from 37 weeks onward. Growth discordance or SGA is associated with higher absolute SB and neonatal risks but does not largely influence the optimal timing of birth.View Large Image Figure ViewerDownload Hi-res image Download (PPT)