Material and methods
Study design
This is a retrospective cohort study that included all women at ≥ 40
years of age and ≥ 39 weeks of gestation that delivered in the city of
Vigo from 1 January 2012 to 31 December 2017. Data were derived from the
Hospital Álvaro Cunqueiro birth cohort, an electronic database created
from gestational, birth, and neonatal data from hospitalisations in the
Vigo delivery room.
Women aged ≥ 40 years with singleton pregnancies were included in the
database. Women with < 39 weeks of gestation and those with
multiple gestations were excluded. In January 2015, the gynaecology and
obstetrics service of Vigo implemented the protocol for induction of
labour due to advanced maternal age; therefore, patients were divided
according to the management of labour at term. We compared expectant
management (women who delivered from 1 January 2012 to 31 December 2014)
to nonmedically indicated induction of labour (women who delivered from
1 January 2015 to 31 December 2017).
The primary outcome was the caesarean delivery rate. The secondary
maternal outcomes were delivery methods other than caesarean section
(that is, assisted vaginal delivery with the use of forceps or vacuum),
the onset of labour (that is, spontaneous labour, elective caesarean
section, or induction of labour), the indication for induction of
labour, the method of labour induction, the indications for caesarean
section, and intrapartum complications (that is, intrapartum fever or
stained amniotic fluid).
The secondary neonatal outcomes were stillbirth, birth weight, the
5-minute Apgar score, the arterial cord pH value, paediatric birth
support, degree of neonatal resuscitation, and admission to a neonatal
intensive care unit (NICU). To analyse the type of paediatric support at
birth, the participants were divided into 3 groups: group 1 included
those new-borns who did not require paediatric assistance at birth;
group 2 included new-borns who required suctioning; group 3 included
those who required the three most advanced degrees of resuscitation,
suctioning and oxygen administration, and use of ambu and intubation.
Basic demographic characteristics and obstetric and clinical outcomes
were examined: parity, smoking status, assisted conception, gestational
age at delivery, history of pregestational diabetes mellitus,
gestational diabetes mellitus, chronic hypertension, and any new
hypertensive disorder during pregnancy (namely, preeclampsia or
gestational hypertension), and pre-pregnancy medical pathology.