Table 3.
Risk Factors for Spontaneous Abortions (SAB) and Stillbirths in Verified Reports Received Following 2009 H1N1Influenza Vaccination, VAERS, October 14, 2009 through February 28, 2010.
| SAB (N=95) | Stillbirths (N=18) | |
|---|---|---|
| Median age years | 32.0 | 29.0 |
| Median onset interval in days a | 7.0 | 7.0 |
| Median duration of pregnancy in weeks b | 8.0 | 30.0 |
| Risk factors c: | N (%) | |
| Advanced maternal age (≥ 35 years of age) | 25 (26.3) | 5 (27.8) |
| Smoking | 7 (7.4) | 3 (16.7) |
| History of intrauterine fetal death | 4 (4.2) | 2 (11.1) |
| Hypothyroidism | 4 (4.2) | 0 |
| Diabetes mellitus d | 3 (3.2) | 2 (11.1) |
| Urinary tract infection | 0 | 5 (27.8) |
| Alcohol or drug use | 2 (2.1) | 4 (22.2) |
| Obesity | 1 (1.1) | 3 (16.7) |
| Other e | 2 (2.1) | 7 (38.9) |
| Pathological findings/observations at delivery: | ||
| Chorioamnionitis | 1 (1.1) | 7 (38.9) |
| Tight nuchal cord | NA | 2 (11.1) |
| Fetal-maternal hemorrhage | NA | 2 (11.1) |
| Fetal growth restriction | NA | 2 (11.1) |
Onset interval unknown for 2 SAB reports. Onset interval is the difference between onset of adverse event and vaccination date.
Duration of pregnancy unknown for 10 SAB reports.
Risk factors are not mutually exclusive; 47 (49.5%) of the 95 had at least one risk factor for a SAB; Among stillbirths, 13 (72.2%) of 18 reports had ≥ 1 maternal risk factor for stillbirth
For SAB reports it includes one case of type II diabetes, type I and history of gestational diabetes; For stillbirth reports it includes on case of type I and one of gestational diabetes
Other risk factors for spontaneous abortion included: chlamydia infection and complicated pregnancy; Other risk factors for stillbirths included: congenital malformations in past pregnancies, uncontrolled diabetes, chronic hypertension, positive Down syndrome screening, chronic hypertension, and macrocytic hyperchromic anemia
NA: not applicable