TABLE 2—
Fetal and Neonatal Outcome Frequencies and Risk Ratios According to Exposure to H1N1 Vaccination During Pregnancy: Ontario, Canada, 2009–2010
| H1N1 Influenza Vaccination During Pregnancy |
||
| Outcome | No (n = 32 230) | Yes (n = 23 340) |
| Preterm birth (< 37 wk)a | ||
| Total no. | 32 091 | 23 280 |
| No. with outcome (rate/100 live births) | 2066 (6.44) | 1 376 (5.91) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.91 (0.85, 0.98) |
| Adjusted RRb (95% CI) | 1.00 (Ref) | 0.95 (0.88, 1.02) |
| Very preterm birth (< 32 wk)a | ||
| Total no. | 32 091 | 23 280 |
| No. with outcome (rate/100 live births) | 271 (0.84) | 141 (0.61) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.71 (0.58, 0.88) |
| Adjusted RRb (95% CI) | 1.00 (Ref) | 0.73 (0.58, 0.91) |
| Small for gestational age: below 10th percentilea | ||
| Total no. | 32 068 | 23 265 |
| No. with outcome (rate/100 live births) | 3 149 (9.82) | 1 937 (8.33) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.83 (0.79, 0.88) |
| Adjusted RRc (95% CI) | 1.00 (Ref) | 0.90 (0.85, 0.96) |
| Small for gestational age: below 3rd percentilea | ||
| Total no. | 32 068 | 23 265 |
| No. with outcome (rate/100 live births) | 864 (2.69) | 466 (2.00) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.74 (0.65, 0.83) |
| Adjusted RRc (95% CI) | 1.00 (Ref) | 0.81 (0.72, 0.92) |
| 5-minute Apgar score below 7a | ||
| Total no. | 31 984 | 23 220 |
| No. with outcome (rate/100 live births) | 413 (1.29) | 277 (1.19) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.92 (0.79, 1.08) |
| Adjusted RRd (95% CI) | 1.00 (Ref) | 0.97 (0.82, 1.14) |
| Fetal death | ||
| Total no. | 32 230 | 23 340 |
| No. with outcome (rate/1000 total births) | 139 (4.31) | 60 (2.57) |
| Unadjusted RR (95% CI) | 1.00 (Ref) | 0.60 (0.44, 0.81) |
| Adjusted RRe (95% CI) | 1.00 (Ref) | 0.66 (0.47, 0.91) |
Note. CI = confidence interval; RR = risk ratio. All adjusted models include maternal age, family income, and education.
a
Among live births only.
b
Also adjusted for chronic hypertension, pregnancy-induced hypertension, preeclampsia, history of preterm birth, and maternal smoking.
c
Also adjusted for neighborhood immigrant concentration, chronic hypertension, and maternal smoking.
d
Also adjusted for neighborhood immigrant concentration, maternal high-risk medical comorbidity, obstetrical complications, intrapartum complications, and gestational age at birth.
e
Also adjusted for maternal smoking.