TABLE 1.
Baseline prevalence of microcephaly and/or brain abnormalities and eye abnormalitiesa potentially related to Zika virus infection, by selected characteristics—Massachusetts, North Carolina, and Atlanta, Georgia, 2013–2014b
| Characteristic | Microcephaly and/or brain abnormalities (%) | Eye abnormalities without brain abnormalities (%) | Total cases (%) |
|---|---|---|---|
| No. of infants or fetuses | 392 | 81 | 473 |
| Infants/fetuses with defects per 1,000 live births (95% CI) | 1.50 (1.35–1.65) | 0.31 (0.25–0.38) | 1.81 (1.65–1.98) |
| Pregnancy outcome | |||
| Live birth | 349 (89) | 81 (100) | 430 (91) |
| Pregnancy lossc | 43 (11) | 0 | 43 (9) |
| Gestational age at delivery (weeks) | |||
| <32 | 68 (17) | 6 (7) | 74 (16) |
| 32–36 | 80 (20) | 18 (22) | 98 (21) |
| 37–41 | 243 (62) | 56 (69) | 299 (63) |
| ≥42 | 1 (<1) | 1 (1) | 2 (<1) |
| Maternal age at delivery (years) | |||
| <25 | 127 (32) | 15 (18) | 142 (30) |
| 25–34 | 178 (45) | 42 (52) | 220 (47) |
| ≥35 | 87 (22) | 24 (30) | 111 (23) |
| Earliest age birth defect was notedd | |||
| Prenatally | 116 (55) | 4 (7) | 120 (45) |
| ≤28 days of delivery | 58 (27) | 29 (54) | 87 (33) |
| 29 days to <3 months | 13 (6) | 10 (18) | 23 (9) |
| 3 months to <6 months | 10 (5) | 3 (6) | 13 (5) |
| ≥6 months | 15 (7) | 8 (15) | 23 (9) |
Case reports were aggregated into two mutually exclusive defect categories: (a) microcephaly (defined as a clinical diagnosis of microcephaly and head circumference at delivery <3rd percentile for sex and gestational age) and/or brain abnormalities, and (b) eye abnormalities without mention of a brain abnormality.
Data from Massachusetts (2013), North Carolina (2013), and three counties in metropolitan Atlanta, Georgia (2013–2014). Total live birth population for the three areas = 261,629.
Includes stillbirths ≥20 weeks gestation, elective terminations after prenatal diagnosis of a malformation at any gestational age and, in Massachusetts, spontaneous pregnancy losses at <20 weeks and <350 g.
The earliest age when a qualifying defect was first noted in the medical record. Data were only available for 266 cases from Massachusetts and metropolitan Atlanta, Georgia.