Table 1.

Study characteristics in a systematic review/meta-analyses on the safest mode of delivery for extremely preterm cephalic/non-cephalic twin pairs

Author, Publication Year, Country; Study Period; Study Design	Inclusion and exclusion criteria	Usual practice regarding twin delivery	Outcomes in original study¥
Boukerrou, 2011 France; 2006–2011; Prospective cohort	Inclusion: All twin births during the study period Exclusion: HOM, stillbirths, births less 24 weeks	For non-cephalic second twin, breech extraction with or without internal podalic version is preferred.	Neonatal death (0–28 days), graded IVH and PVL (in provided data only)
Barzilay, 2015 Israel; 2004–2011; Retrospective cohort	Inclusion: All twin births with second twin birthweight less 1500 g Exclusion: Birth less 24 weeks, fetal death of one or both twins, major malformation in one or both twins	Allow vaginal delivery of cephalic-non-cephalic twin pairs regardless of EFW or GA if EFW of twin B is not 20% higher than that of twin A. Breech extraction is preferred for delivering non-cephalic twin B.	Apgar 5 min, Cord blood PH, Neonatal death (not otherwise specified), Birth trauma, RDS, Sepsis, NEC, IVH, Composite adverse neonatal outcome (neonatal death, RDS, sepsis, NEC, or IVH grade ≥ 3)
Bricelj, 2016 Slovenia; 2003–2012; Retrospective cohort	Inclusion: All deliveries from 22 weeks or birth weight 500 g up to less than 37 weeks Exclusion: Delayed births, combined deliveries, stillbirths (in provided data only)	Not stated	TTN, RDS, Ventilation need

HOM high order multiple pregnancies, EFW estimated fetal weight, GA gestational age, IVH intraventricular hemorrhage, PVL periventricular leukomalacia, RDS respiratory distress syndrome, NEC necrotizing enterocolitis, TTN transient tachypnea of the newborn ^¥ Outcomes provided by the authors for twins less 28 weeks are bolded