Birth weight in pre-eclamptic and normotensive twin pregnancies: an analysis of discordance and growth restriction

The aim of this study was to verify whether twin pregnancies complicated by pre-eclampsia were associated with a higher rate of inter-twin weight disc ordance or an increased prevalence of small for gestational age (SGA) neona tes than in normotensive twin pregnancies. A 17 year retrospective study wa s undertaken by examining 76 twin pregnancies complicated by pre-eclampsia and comparing them with 400 normotensive twin pregnancies. The case notes w ere reviewed in reference to birth weight differences, birth order, pregnan cy outcome and inter-twin birth weight discordance. Statistical analyses we re performed with t-test, contingency tables, regression curves, rank sum t est and non-parametric survival plots. Power analysis was also carried out. Pre-eclamptic twin pregnancies were delivered at similar weeks of gestatio n to normotensive. They resulted in a smaller size for the second twin the earlier the delivery week, while in normotensive twin pregnancies no signif icant difference occurred at any week, Twin pregnancies complicated by pre- eclampsia showed higher rates of SGA neonates among second twins than those with normal pressure. The >25% discordance was associated with lower gesta tional age at delivery in each group [mean (range) 33 weeks (27-38) versus 37 (29-41), P < 0.005 pre-eclampsia and 35 weeks (25-41) versus 38 (25-42), P < 0.001 normotensive], In pre-eclampsia the concomitant occurrence of SG A second twin and the discordance >25% was associated with shorter gestatio n while the presence of SGA second twin alone was not.