Study design, setting and population
This is a retrospective cohort study conducted at Virgen del Rocío
University Hospital of Seville (a tertiary referral center with about
6000 births per year), including all women with uncomplicated MCDA
pregnancies who had a birth at 32.0 – 37.6 weeks of gestation from
January 2012 to December 2018.
Chorionicity was determined by first-trimester ultrasonography and
confirmed after birth by pathological examination. In all cases a
detailed anomaly scan was performed at 18.0 – 21.6 weeks. Specific
management protocols for MCDA twins were determined locally following
national and international guidelines, as those established by the Royal
College of Obstetricians and Gynaecologists
(RCOG)[24] or the International Society of
Ultrasound in Obstetrics and Gynecology
(ISUOG)[25].
Cases were classified into trial of labor (TOL) or PCS groups depending
on the intended method of delivery. A TOL was planned if twin A was in
vertex presentation after 32 weeks of gestation, estimated fetal weight
was at least 1500 g, and there was no contraindication for vaginal
delivery (non-vertex first twin, at least two previous CS, weight
discordance > 15% when first twin was smaller, vasa
previa, and/or any other condition like active herpes genital
infection). Deliveries were included as TOL when the onset of labor was
spontaneous or induced, and in all cases both fetuses were monitored
intrapartum by continuous cardiotocography. In cases of non-vertex
presentation of the second twin, breech extraction was performed by a
senior obstetrician. The maximum time to perform an emergent CS was 10
minutes after decision.
A PCS was in most cases established when the first twin was in a
non-vertex presentation. In no cases, a PCS was performed because of
maternal request. At least two obstetricians and neonatologists were
always present in the delivery room (from the second stage of labor) as
well as in the operating room.