General characteristics
A total of 2532 articles were identified, 57 were assessed with respect
to their eligibility for inclusion, and 10
studies17-26 were deemed suitable to be included in
this systematic review (Table S1;
Figure S1). These 10 studies
(including 304181 twin pregnancies) reported the occurrence of
birthweight discordance in twin pregnancies complicated by GHD compared
with those not. Eight of these included papers were cohort studies,
whereas two were case-control studies17,19. Three of
them were conducted in China19,24,26, two in the
USA21,22, two in the UK17,25, two in
Rome18,20 and one in Ireland23.
Among the selected studies, four reported the intertwin birthweight
discordance affected by GH17,18,24,26, three affected
by CH17,21,22 and five affected by
PE19-21,24,26 in detail. Only three of the included
studies24-26 conducted stratification by twin
chorionicity.
Quality assessment of the selected studies performed using NOS is
presented in Table S2. Most of the studies scored well in terms of
selection, comparability and outcome. The main weaknesses of these
studies were their retrospective design, small sample size, lack of
information on the follow-up outcome, different gestational ages at scan
and heterogeneity in the cut‐off of birthweight discordance adopted.