TABLE 2.

Analysis of birth outcomes by maternal vaccination status and influenza exposure, N = 4084, Cape Town, South Africa, 2015‐2016

Outcome	All N = 4084	Vaccinated n = 2109 (51.6%)	Unvaccinated n = 1975 (48.4%)	Crude Weight Difference or Odds Ratio in Vaccinated vs Unvaccinated (95% CI)	Adjusted Effect in Vaccinated vs Unvaccinated (95% CI)	Propensity score matched Effect in Vaccinated vs Unvaccinated (95% CI)	Inverse probability weighted Effect in Vaccinated vs Unvaccinated (95% CI)
Mean birth weight † , g (95% CI)	3150 (3133‐3167)	3205 (3183‐3227)	3091 (3064‐3117)	114 (80 to 148)	20 (−11 to 51) ‡ a	NA	36 (1 to 70) §
Proportion low birth weight † , n/N (%)	390/4053 (9.6)	146/2102 (6.9)	244/1951 (12.5)	0.52 (0.42 to 0.65)	0.27 (0.07 to 0.42) b	0.30 (0.09 to 0.51)	0.24 (0.04 to 0.45)
Proportion preterm † , n/N (%)	500/4051 (12.3)	180/2101 (8.6)	320/1950 (16.4)	0.48 (0.39 to 0.58)	0.26 (0.09 to 0.40) b	0.25 (0.09 to 0.41)	0.34 (0.18 to 0.51)
Proportion small for gestational age † , n/N (%)	298/4049 (7.4)	126/2101 (6.0)	172/1948 (8.8)	0.66 (0.52 to 0.84)	0.15 (−0.10 to 0.34) b	0.15 (−0.08 to 0.38)	0.22 (−0.01 to 0.45)
Proportion stillbirth, n/N (%)	30/4084 (0.7)	6/2109 (0.3)	24/1975 (1.2)	0.23 (0.09 to 0.57)	0.62 (0.04 to 0.85) c	0.61 (−0.07 to 1.30)	0.49 (−0.25 to 1.24)

^aAdjusted for gestational age, site, parity, number of antenatal visits, maternal HIV status, and smoking during pregnancy.

^bAdjusted for site, parity, number of antenatal visits, and smoking during pregnancy.

^cAdjusted for campaign year, site, and number of antenatal visits.

^†low birthweight (birthweight less than 2500 g), preterm birth (less than 37 weeks gestational age), and small for gestational age (birthweight <10^th percentile for gestational age using WHO fetal growth charts) among live births with birth weight reported (n = 4053).

^‡linear regression coefficient for birth weight which is a continuous variable (n = 3986).

^§inverse probability weighting with regression adjustment (n = 3837).