Table 2 Meta-analysis of maternal and perinatal outcomes in studies comparing COVID-19 vaccinated and unvaccinated pregnancies.

Outcome	Studies (n)	Vaccinated (n)	Unvaccinated (n)	Effect estimate*	P	I² (%)
Miscarriage	2^27,29	15,684	108,249	1.00 (0.92– 1.09)	0.988	19.8
Fetal anomalies	2^8,20	335	523	0.91 (0.40– 2.06)	0.820	0.0
Stillbirth	7^{8,21,24,30,31,32,33}	66,067	425,624	0.85 (0.73–0.99)	0.035	93.9
GA at birth	4^8,24,31,34	3145	6375	−0.04 (−0.30 to 0.29)	0.966	85.3
PTB < 37 weeks’ gestation	6^{8,24,28,31,32,33}	37,195	369,924	0.89 (0.73– 1.09)	0.269	96.8
PTB < 34 weeks’ gestation	2^8,31	845	1462	0.88 (0.53– 1.48)	0.634	0.0
PTB < 32 weeks’ gestation	3^8,32,33	25,032	331,419	0.81 (0.34–1.92)	0.627	56.6
PTB < 37 weeks’ gestation adjusted for time-varying confounding	2^8,28	10,197	36,414	0.90 (CI 0.81–1.00)	0.051	0.0
Low BW (<2500 g)	2^32,33	24,899	331,020	0.99 (0.93–1.04)	0.621	0.0
SGA at birth	4^8,28,31,34	10,686	36,647	1·00 (0·93 – 1·08)	0.918	16.9
BW, Z-score	2^8,19	219	461	0.0 (−0.17 to 0.18)	0.956	0.0
BW, grams	3^24,31,34	3012	5976	−5.88 (−28.8 to 16.0)	0.598	0.0
Asphyxia	2^31,32	852	2925	0.29 (0.09–1.00)	0.049	0.0
5-min Apgar score < 7	3^31,32,34	1765	6411	0.78 (0.37– 1.61)	0.499	46.7
NICU admission	3^8,31,32	985	3324	0.94 (0.63– 1.40)	0.764	0.0

All P values are two-sided without any adjustments. Effects estimates were pooled using one of the following estimators (maximum-likelihood, restricted maximum-likelihood, inverse variance)
BW birthweight, GA gestational age, n number, NICU neonatal intensive care unit, PTB preterm birth, SGA small for gestational age
^aEffect estimates are reported as odds ratio (binary outcomes), mean difference (continuous outcomes), hazard ratio (preterm birth adjusted for time varying confounding and 95% confidence intervals.

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