Table 2. Risks for Spontaneous Abortion (SAB), Preterm Birth, Small-for-Gestational Age Birth (SGA), and Major Structural Birth Defects by Human Papillomavirus Vaccine Exposure Windowa.
| Variable | No. (%) | Risk of event | ||||
|---|---|---|---|---|---|---|
| Distal exposure | Peripregnancy exposure | During-pregnancy exposure | Peripregnancy vs distal exposure | During pregnancy vs distal exposure | During pregnancy or peripregnancy vs distal exposure | |
| Pregnancies, No. | 552 | 496 | 445 | NA | NA | NA |
| SAB | 33 (6.0) | 22 (4.4) | 25 (5.6) | RR (95% CI): 0.72 (0.42-1.24)b | HR (95% CI): 1.12 (0.66-1.93)c | HR (95% CI): 1.20 (0.77-1.88)c |
| Live births with gestational age, No. | 518 | 474 | 418 | NA | NA | NA |
| Preterm birthsd | 42 (8.1) | 27 (5.7) | 26 (6.2) | RR (95% CI): 0.72 (0.45-1.17)c | RR (95% CI): 0.73 (0.44-1.20)c | RR (95% CI): 0.75 (0.50-1.13)c |
| Live births with gestational age and birth weight, No. | 425 | 388 | 341 | NA | NA | NA |
| SGA birthse | 27 (6.4) | 27 (7.0) | 29 (8.5) | RR (95% CI): 1.10 (0.65-1.88)c | RR (95% CI): 1.31 (0.78-2.20)c | RR (95% CI): 1.18 (0.75-1.85)c |
| Live births with follow-up, No.f | 414 | 363 | 320 | NA | NA | NA |
| Major structural birth defects | 4 (1.0) | 4 (1.1) | 4 (1.3) | PR (95% CI): 1.03 (0.26-4.07)g | PR (95% CI): 1.30 (0.36-4.69)g | PR (95% CI): 1.06 (0.34-3.33)g |
Abbreviations: HR, hazard ratio; LMP, last menstrual period; NA, not applicable; PR, prevalence ratio; and RR, relative risk.
Exposure windows: distal consisted of 9vHPV or 4vHPV vaccine administered from 22 to 16 weeks before LMP, peripregnancy consisted of 9vHPV vaccine administered from 42 days before LMP until LMP, during pregnancy consisted of 9vHPV vaccine administered from LMP to 19 completed weeks’ gestation.
Using 9vHPV or 4vHPV vaccine, with inverse probability weights for age, race/ethnicity, hospitalization before pregnancy, smoking, and site.
Using 9vHPV or 4vHPV vaccine as a time-dependent exposure in a Cox proportional hazards regression model, with inverse probability weights for age, race/ethnicity, hospitalization before pregnancy, smoking, and site.
Preterm birth defined as live birth before 37 weeks’ gestation.
SGA birth defined as below 10th percentile, based on Talge et al.27
For evaluation of birth defect outcomes, infants who survived the first year were required to have at least 1 outpatient visit in the health system, 4 months of insurance in the first year of life, and no diagnosis of a chromosomal anomaly.
Using 9vHPV or 4vHPV vaccine, with inverse probability weights for age, race/ethnicity, hospitalization before pregnancy, smoking, and site.