Methods
The current study was conducted at the Unit of Obstetrics and
Gynaecology of the San Paolo Hospital, Medical School in Milano, Italy.
The Unit is a secondary referral centre, i.e. comprises a maternal
intensive care unit (ICU) but not neonatal ICU. The audit system in our
institution involves a weekly discussion of relevant clinical cases, the
use of standardized and up-to-date protocols and the publication of an
annual report about labour, delivery, maternal and neonatal outcomes of
all women. The majority of the non-Italian women delivering in our Unit,
are assisted by a non-profit social cooperative that deals with cultural
mediation. Data were obtained from an electronic database that includes
information on deliveries that occurred in our clinic from 1996 to 2019.
Data were already available for the analysis for all women as part of
the annual clinical report of the Unit. Obstetric outcomes, maternal and
fetal characteristics included in the database are collected from
medical records at the end of each month by residents in Obstetrics and
Gynaecology. The database includes all the live births and stillbirths
from 23 weeks of gestational age. The board of the San Paolo Department
of Health Sciences approved the study protocol. When information on
parity, number of fetuses, previous caesarean section, onset of labour,
gestational age, and fetal presentation were all available, women were
classified according to the modified TGCS; for the purpose of the
analysis we selected women belonging to Group 1 (nulliparous, single
cephalic, ≥37 weeks, in spontaneous labour), 2A (nulliparous, single
cephalic, ≥37 weeks, induced), 3 (multiparous, excluding previous CS,
single cephalic, ≥37 weeks, in spontaneous labour, 4A (multiparous,
excluding previous CS, single cephalic, ≥37 weeks, induced) and 10 (all
single cephalic, ≤36 weeks). We also included in the regression analysis
women of Group 5 (previous CS, single cephalic, ≥37 weeks) only if they
attempted a trial of labour after caesarean (TOLAC). Hereafter we will
refer to these women as Group 5. We excluded from the analysis women of
Groups 2B (nulliparous, single cephalic, ≥37 weeks, CS before labour),
4B (multiparous, excluding previous CS, single cephalic, ≥37 weeks, CS
before labour), 6 (all nulliparous breeches), 7 (all multiparous
breeches), and 9 (all abnormal presentations) because they underwent
elective caesarean sections as for protocol. We also excluded multiple
pregnancies (group 8) due to the presence of several potentially
confounding factors and to the limited population The analysis was
conducted inside each group and not between groups. Induction of labour
was defined as the use of any mechanical method (intrauterine Foley
catheter or Cervical Ripening Balloon), medication (prostaglandins or
oxytocin) or amniotomy when not in labour.
The CS rate was calculated for each group as the number of CS out of the
number of all the deliveries. We also calculated the CS rate per year in
each group. The impact of advanced age (maternal age equal to or higher
than 40 year), diabetes (including pre-pregnancy diabetes mellitus and
gestational diabetes mellitus), hypertensive disease (including
pregestational hypertension, gestational hypertension, preeclampsia or
eclampsia), fetal macrosomia (neonatal birthweight higher than 4000 g),
obesity (pre-pregnancy body mass index ≥30 kg/m2),
obstetric analgesia and immigrant status was evaluated. Gestational
diabetes mellitus and hypertensive disease of pregnancy were diagnosed
according to the guidelines available at the time of the pregnancy. The
dependent variable was the type of delivery, i.e. vaginal (both
spontaneous or operative) or caesarean section. The variable macrosomia
was not included in the analysis of group 10 because all the newborn
weighed less than 4000 g. A binomial logistic regression was performed
to ascertain the effects of variables on CS rates and odds ratio were
calculated. For missing values, listwise deletion approach was applied.
Linear regressions and Anova tests were performed to evaluate temporal
trends in CS rates for considered Robson groups.
All calculations were performed using SPSS version 25.0 (SPSS Inc,
Chicago, IL, USA). A p-value lower than 0.05 was considered
statistically significant.