Table 5

Summary of risk of bias assessment for individual studies based on an adapted Newcastle-Ottawa Scale

	Exposure*				Outcome†				Total stars
	Representativeness of exposed cohort	Selection of non-exposed cohort	Ascertainment of exposure (SARS-CoV-2 infection)	Ascertainment of control (SARS-CoV-2 negative)	Outcome assessment data source	Adequacy pregnancy follow-up		Data completeness‡	Total stars
Akelo and Tippett Barr (2021)	*	*	*	*	*	§	(a) Critical care	N/A	N/A
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	N/A	N/A
							(d) Adverse birth outcomes	¶	5/7
Le Doare (2021)	**	*	††	*	*	*	(a) Critical care	N/A	N/A
							(b) Maternal mortality and morbidity	*	5/7
							(c) Fetal and neonatal mortality	*	5/7
							(d) Adverse birth outcomes	*	5/7
Crovetto (2020), Cohort I	*	*	*	*	*	§	(a) Critical care	*	6/6
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	*	6/7
							(d) Adverse birth outcomes	*	6/7
Poon (2021)	**	*	*	*	*	*	(a) Critical care	*	5/6
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	*	6/7
							(d) Adverse birth outcomes	*	6/7
Crovetto (2020), Cohort II	*	*	*	*	*	*	(a) Critical care	*	6/6
							(b) Maternal mortality and morbidity	*	7/7
							(c) Fetal and neonatal mortality	*	7/7
							(d) Adverse birth outcomes	*	7/7
Bevilacqua and Laurita Longo (2020)	**	*	*	*	*	*	(a) Critical care	*	5/6
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	*	6/7
							(d) Adverse birth outcomes	*	6/7
Nachega (2021)	**	*	*	*	*	§	(a) Critical care	¶	4/6
							(b) Maternal mortality and morbidity	¶	4/7
							(c) Fetal and neonatal mortality	*	5/7
							(d) Adverse birth outcomes	¶	4/7
Nunes (2021)	**	*	*	*	*	*	(a) Critical care	N/A	N/A
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	*	6/7
							(d) Adverse birth outcomes	*	6/7
Sakowicz et al 23	**	*	*	*	*	*	(a) Critical care	*	5/6
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	¶	5/7
							(d) Adverse birth outcomes	*	6/7
Ahlberg et al 19	*	*	*	*	*	*	(a) Critical care	N/A	N/A
							(b) Maternal mortality and morbidity	*	7/7
							(c) Fetal and neonatal mortality	*	7/7
							(d) Adverse birth outcomes	*	7/7
Kalafat et al 22	**	*	*	*	*	*	(a) Critical care	*	5/6
							(b) Maternal mortality and morbidity	*	6/7
							(c) Fetal and neonatal mortality	*	6/7
							(d) Adverse birth outcomes	*	6/7
Brandt (2020)	*	*	*	*	*	*	(a) Critical care	*	6/6
							(b) Maternal mortality and morbidity	*	7/7
							(c) Fetal and neonatal mortality	*	7/7
							(d) Adverse birth outcomes	*	7/7

Stars (*) indicate a study is at lower risk of bias in a given domain.
*See online supplemental table S6 for detailed risk of bias assessment related to selection of the exposed and unexposed cohorts for individual studies.
†See online supplemental table S6 for detailed risk of bias assessment related to outcome assessment for individual studies.
‡See online supplemental table S8 for a description of follow-up by study and review of missing data by outcome.
§Pregnancy follow-up domain deemed at higher risk of bias because <90% of pregnancy outcomes had been ascertained at the time of data transfer.
¶Data completeness domain deemed at higher risk of bias because one or more outcomes in this category had missing data for 11%–25% of participants.
**Representativeness of the exposed cohort domain deemed at higher risk of bias because 50% or more of the cases were identified using a method that was only somewhat representative of all SARS-CoV-2-infected pregnant women in the community (eg, pregnant women tested at antenatal care of delivery based on symptoms or travel; pregnant women tested for antibodies during routine screening; medical records of pregnant women hospitalised for any reason, excluding delivery).
††Ascertainment of exposure (SARS-CoV-2 infection) domain deemed at higher risk of bias because a proportion of COVID-19-positive cases were identified through clinical diagnosis or radiography consistent with WHO case definitions of probable and suspected cases.
N/A, not available.