Table 2.

Studies Reporting Birth Outcomes With Trivalent Inactivated or H1N1 Influenza Vaccine Administered During Pregnancy

First Author	Site	Trial Design	Intervention	Control	Risk of Preterm Birth (95% CI)	Risk of Low Birth Weight (95% CI)	Risk of Small for Gestational Age (95% CI)
Omer, 2011 [27]	Georgia, USA	Retrospective cohort analysis	TIV N = 578	No vaccine N = 3748	OR: 0.28 (.11–.74)	…	OR: 0.31 (.13–.75)
Steinhoff, 2012 [28]	Dhaka, Bangladesh	Randomized controlled clinical trial	TIV N = 172	Pneumococcal polysaccharide vaccine N = 168	OR: 0.48 (.08–2.74)	OR: 0.19 (.02–1.64)	OR: 0.43 (.20–.94)
Kallen, 2012 [29]	Sweden	Retrospective population-based cohort analysis	H1N1 vaccine N = 18 612	No vaccine N = 136 914	OR: 0.86 (.77–.96)	OR: 0.86 (.77–.96)	OR: 1.04 (.92–1.17)
Fell, 2012 [30]	Ontario, Canada	Retrospective population-based cohort analysis	H1N1 vaccine N = 23 340	No vaccine N = 32 230	RR: 0.73 (.58–.91)	…	RR 0.90 (.85–.96)
Pasternak, 2012 [24]	Denmark	Retrospective population-based cohort study	H1N1 vaccine N = 6989 infants	No vaccine N = 46 443 infants	1st trimester: OR: 1.32 (.76–2.31) 2nd/3rd trimester: OR: 1.00 (.84–1.17)	1st trimester: OR: 0.83 (.41–1.67) 2nd/3rd trimester: OR: 1.14 (.94–1.38)	1st trimester: OR: 0.79 (.46–1.37); 2nd/3rd trimester: OR: 0.97 (.87–1.09)
Richards, 2013 [31]	Georgia, USA	Retrospective cohort analysis	H1N1 vaccine N = 1125	No vaccine N = 1581	OR: 0.63 (.47–.84)	OR: 0.79 (.56–1.10)	OR: 1.26 (.94–1.69)

Adapted from Steinhoff and Omer [26].

Abbreviations: CI, confidence interval; OR, odds ratio; RR, relative risk; TIV, trivalent inactivated influenza vaccine.