Table 2.
Unadjusted incidence of select adverse twin birth outcomes stratified by maternal prepregnancy body mass index, Pennsylvania twin birth certificates, 2003–2013.
| Prepregnancy body mass index* | Births | Small-for-gestational-age birth | Large-for-gestational-age birth | Preterm birth <32 weeks | Cesarean delivery | Infant death | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Total, n | Cases, n | % | Cases, n | % | Cases, n | % | Cases, n | % | Cases, n | % | |
| Underweight | 1858 | 370 | 20 | 88 | 4.7 | 291 | 16 | 1093 | 59 | 75 | 4.0 |
| Normal weight | 26,011 | 3323 | 13 | 1756 | 6.8 | 3183 | 12 | 16,979 | 65 | 675 | 2.6 |
| Overweight | 13,373 | 1531 | 11 | 1146 | 8.6 | 1667 | 12 | 9237 | 69 | 409 | 3.1 |
| Grade 1 obese | 7153 | 864 | 12 | 627 | 8.8 | 865 | 12 | 5120 | 72 | 262 | 3.7 |
| Grade 2 obese | 3684 | 403 | 11 | 403 | 11 | 485 | 13 | 2668 | 72 | 136 | 3.7 |
| Grade 3 obese | 2757 | 285 | 10 | 317 | 12 | 376 | 14 | 2164 | 78 | 117 | 4.2 |
*
Underweight (<18.5 kg/m2), normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2), grade 1 obese (30–34.9 kg/m2), grade 2 obese (35–39.9 kg/m2), or grade 3 obese (≥40 kg/m2)