Eight studies (three retrospective and five prospective) were included. The total number of participants was 44,829 (range 416 to 23,316). Most studies met the criteria for adequate participant selection and half of the studies reported adequate test standardisation and loss to follow-up. One study reported blinding of medical staff.
Perinatal outcomes: Statistically significant associations were reported between WHO diagnostic criteria and foetal macrosomia (RR 1.81, 95% CI 1.47 to 2.22; five studies; Ι²=0%) and large for gestational age births (RR 1.53, 95% CI 1.39 to 1.69; four studies; Ι²=0%). There was no statistical association between WHO criteria and perinatal mortality (two studies; Ι²=0%). For IADPSG criteria there were statistically significant associations for foetal macrosomia (using the EBDG database: RR 1.38, 95% CI 1.14 to 1.68) and large for gestational age births (RR 1.73, 95% CI 1.28 to 2.35; three studies; Ι²=93%). There was no statistical association for perinatal mortality (using the EBDG database).
Maternal outcomes: Statistically significant associations were reported between WHO diagnostic criteria and pre-eclampsia (RR 1.69, 95% CI 1.31 to 2.18; three studies; Ι²=38%) and caesarean delivery (RR 1.37, 95% CI 1.24 to 1.51; four studies; Ι²=29%). For IADPSG criteria, statistically significant associations were reported for pre-eclampsia (RR 1.71, 95% CI 1.37 to 2.14; three studies; Ι²=73%) and for caesarean delivery (RR 1.23, 95% CI 1.01 to 1.51; three studies; Ι²=93%).
Sensitivity analyses did not substantially alter the main findings (results reported in the paper).