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.