Twin Pregnancies Conceived by Assisted Reproductive Technology: Maternal and Perinatal Outcomes

Association between chorionicity and preterm birth in twin pregnancies: a systematic review involving 29 864 twin pregnancies

“…28,41 Seven of the 39 studies (18%) reported on pregnancies which are asymptomatic for preterm labour 20,22,34,38,45,50,51 whereas 31 studies reported on pregnancies which were both symptomatic and asymptomatic for preterm labour. 4,[14][15][16][17][18][19]21,23,24,[26][27][28][29][30][31][32][33][35][36][37][39][40][41][42][43][44][46][47][48][49] Seven studies (18%) reported on treatment or prophylaxis for preterm labour. 36,37,39,42,48,50,51 Around 80% (31/39) of the studies reported on both spontaneous and iatrogenic preterm birth 4,38,…”

“…In all, 97% of the studies were low risk for study selection (38/ 39), 4,14-38,40-51 10% (4/39) were low risk for comparability 28,32,40,49 and all studies were low risk for study outcome (100%). 4, One study had a medium risk of bias for study selection (3%), 39 32 studies for comparability 4,14,15,17,[20][21][22][23][24][25][26][27][29][30][31][33][34][35][36][37][38][39][41][42][43][44][45][46][47][48]50,51 and none of the studies had a medium risk of bias for outcome. None of the studies had a high risk of bias for selection or outcome; however, three studies were of high risk for comparability.…”

“…Monochorionicity was studied as a predictor of preterm birth at ≤28 weeks in 11 studies (10 484 pregnancies), 4,18,20,23,26,32,38,41,44,47,48 ≤32 weeks in 23 studies (19 783 pregnancies), 4,[14][15][16]19,20,[23][24][25][27][28][29]32,[36][37][38][39]41,45,[47][48][49][50] ≤34 weeks in 22 studies (21 181 pregnancies) 4,15,[18][19][20]24,[26][27][28][30][31][32]38,40,[43][44][45]…”

“…Of the 39 studies, 29 were retrospective cohorts, 4,14–41 eight were prospective cohorts 42–49 and two were cohorts nested within randomised controlled trials 50,51 . Thirty‐two studies were conducted in high‐income countries (USA 6, UK 6, Portugal 5, Italy 4, Denmark 3, Korea 2, Germany 1, Austria 1, Israel 1, Taiwan 1, Poland 1, Canada 1, France 1, Sweden 1, Netherlands 1), five in upper‐middle‐income countries (Brazil 2, China 2, Iran 1) and two in a middle‐income country (Pakistan).…”

“…Seven of the 39 studies (18%) reported on pregnancies which are asymptomatic for preterm labour 20,22,34,38,45,50,51 whereas 31 studies reported on pregnancies which were both symptomatic and asymptomatic for preterm labour 4,14–19,21,23,24,26–33,35–37,39–44,46–49 . Seven studies (18%) reported on treatment or prophylaxis for preterm labour 36,37,39,42,48,50,51 .…”