. 2020 Jul 8;20:395. doi: 10.1186/s12884-020-03036-1

Table 3.

Results of primary and subgroup meta-analyses by outcome

Meta-analyses	Studies	References	Patients n	Shape of association	Risk ratio	95% CI	I²
NICU admission all	14	[25, 37, 39, 51, 52, 54–56, 60, 62, 63, 65, 68, 69]	898,272	Linear dose-response^a	0.63	0.56–0.71	95.4
Neonatal death	4	[37, 40, 62, 65]	533,880	U-Shape^b	< 39: 0.59 ≥39: 2.09	0.43–0.83 1.18–3.70	77.5
Respiratory morbidity	9	[51, 53, 55, 57, 58, 61, 64, 65, 68]	57,693	Linear dose-response^a	0.64	0.51–0.79	95.2
Hospitalization ≥5 days	5	[38, 62, 65, 68, 69]	59,331	U-Shape^b	< 39 0.52 ≥39 2.00	0.36–0.75 1.40–2.86	96.2
Sepsis	4	[37, 52, 65, 68]	42,381	U-Shape^b	< 39 0.55 ≥39 3.57	0.44–0.67 1.87–6.78	21.8
Hypoglycemia	6	[25, 38, 60, 65, 68, 69]	46,367	Linear dose-response^a	0.84	0.79–0.91	0.0
Apgar Score < 7	5	[39, 56, 60, 65, 69]	805,274	Linear dose-response^a	0.90	0.69–1.17	65.7
Jaundice	5	[56, 60, 65, 68, 69]	32,109	Linear dose-response^a	0.71	0.66–0.77	53.7
Respiratory distress syndrome	5	[37, 59, 60, 65, 69]	43,888	Linear dose-response^a	0.60	0.54–0.67	45.0
Transient tachypnea of the newborn	5	[37, 55, 59, 60, 65]	40,766	Linear dose-response^a	0.68	0.54–0.86	84.1
Pneumothorax	4	[44, 59, 60, 67]	25,121	Binary (37 + 38 WG vs. ≥39 WG)^c	0.99	0.03–39.19	72.0
Maternal hysterectomy	2	[37, 52]	18,662	Binary (37 + 38 WG vs. ≥39 WG)^c	1.10	0.03–39.35	0.0
Maternal blood transfusion	2	[37, 60]	15,162	Binary (37 + 38 WG vs. ≥39 WG)^c	1.21	0.02–65.67	30.0
Meta-analyses of subgroups
NICU admission only ERCS	4	[37, 39, 54, 60]	792,107	Linear dose-response^a	0.66	0.65–0.67	0.0
NICU death only repeat CS	2	[37, 40]	497,917	U-Shape^b	< 39 0.67 ≥39 1.68	0.51–0.87 1.07–2.65	0.0

NICU Neonatal Intensive Care Unit; WG Week of gestation

^a Starting at 37 WG, RR for each additional WG

^b Starting at 39 WG, RR for each fewer WG and RR for each additional WG

^c Comparison of two timeframes; 37 + 38 WG = 37 + (0–6) + 38 + (0–6), 39 WG = 39 + 0