Table 1 Inclusion/exclusion criteria and patient characteristics

Allen 2020

Inclusion criteria:

All births ≥ 37 WG.

Exclusion criteria:

Paid by other than Medicaid or private insurance.

NR

Dunn 2013

Inclusion criteria:

All ERCS ≥ 37 WG in “Low-risk women”.

Exclusion criteria:

Women, who were in labour, had a medical history or pregnancy-related complications.

ERCS n, 459/497

Gurol-Urganci 2014

Inclusion criteria:

All ECS ≥ 37 WG.

Singleton elective caesarean delivery episodes in NHS trusts (which had data for at least 50% of their deliveries in at least 7 years) from 1 April 2000 to 28 February 2009. Included if their HES record contained the code of ECS in any of the core operative procedure fields.

Exclusion criteria:

Women who had an ECS < 34 weeks or a medical history. (e.g., preexisting and gestational diabetes, hypertensive disorders, preeclampsia, eclampsia, premature rupture of membranes, poly- and oligohydramnios, excessive or poor foetal growth, and placenta praevia).

ECS n, 118,456

Hutcheon 2015

Inclusion criteria:

All ECS ≥ 37 WG for a primary indication of breech, repeat CS, or maternal request/vaginal birth after CS declined.

Exclusion criteria:

Pregnancies complicated by diabetes in pregnancy, antepartum haemorrhage, hypertension in pregnancy, or other comorbidities that might be an indication for an earlier delivery.

ECS n, 2021/2518

Maternal age, mean in years (SD):

33.7 (4.6)/34.1 (4.7)

Nulliparous n (%):

352 (17.4)/486 (19.3)

Prepregnancy BMI (kg/m2) n (%):

Underweight (< 18.5), 80 (4.0)/93 (3.7)

Normal weight (18.5–24.9), 872 (43.1)/1050 (41.7)

Overweight (25–29.9), 254 (12.6)/352 (14.0)

Obese (≥ 30), 98 (4.9)/137 (5.4)

Missing, 717 (35.5)/886 (35.2)

WG at delivery median in (days) (range), 271 (268–274)/273 (270–276)

Birthweight mean in g (SD):

3420 (425)/3421 (426)

MacAllister 2019

Inclusion criteria:

All ECS ≥ 37 WG (= absence of labour and no maternal or foetal indication for urgent delivery).

Exclusion criteria:

NR

ECS n, 19,780/40,875

Nicholl 2010

Inclusion criteria:

All ECS ≥ 37 WG for ERCS, breech presentation, or maternal request.

Exclusion criteria:

Medical indication

NR

Nicoll 2004

Inclusion criteria:

All ECS ≥37 WG (= timing of delivery could be postponed without any risk to the mother or foetus)

Exclusion criteria:

NR

ECS n, 292/327

Snowden 2016

Eligibility criteria:

All ECS ≥ 37 WG (= without medical or obstetrical indication).

Exclusion criteria:

Women with a medical history or pregnancy-related complications (e.g., chronic hypertension, prepregnancy diabetes, and gestational diabetes mellitus).

ECS n, 12,204/7,697

Tanger 2010

Inclusion criteria:

All ECS ≥37 WG

Exclusion criteria:

Women with a medical history or pregnancy-related complications (e.g., preeclampsia, maternal infection, (suspicion of) foetal distress, severe birth defects of the foetus, maternal gestational diabetes or diabetes mellitus).

ECS n, 324/486

Maternal age, mean in years (SD):

36.4 (4.7)/34.8 (4.2)

Multiples n (%), 9 (3)/15 (3)

Female n (%), 167 (50)/254 (51)

Birthweight mean in g (SD):

3282 (470)/3386 (494)

Apgar score after 5 min < 6; n (%), 0/0

Yamasato. 2014

Inclusion criteria:

All ECS ≥ 37 WG.

Exclusion criteria:

Medical indication

NR