Table 3.
Risk of adverse outcomes by number of embryos transferred and number of fetal heartbeats
| Outcome | ET-FHB groups | Singletons at birth | Twins at birth | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| ET | FHB | Rate** | AOR | 95% CI | ET | FHB | Rate** | AOR | 95% CI | ||
| Major defects*** | Reference | 1 | 1 | 228.6 | 1.00 | Reference | 2 | 2 | 324.8 | 1.00 | Reference |
| Excess ET | 2 | 1 | 241.5 | 1.13 | 1.00, 1.27 | 3 | 2 | 321.9 | 1.10 | 0.95, 1.26 | |
| ≥3 | 1 | 232.3 | 1.18 | 1.00, 1.38 | ≥4 | 2 | 286.8 | 1.03 | 0.81, 1.32 | ||
| Excess ET + FHB | ≥2 | ≥2 | 235.4 | 1.12 | 0.92, 1.38 | ≥3 | ≥3 | 311.5 | 1.09 | 0.85, 1.41 | |
| ET | FHB | % | AOR | 95% CI | ET | FHB | % | AOR | 95% CI | ||
| Small-for-gestation birthweight | Reference | 1 | 1 | 7.0 | 1.00 | Reference | 2 | 2 | 19.8 | 1.00 | Reference |
| Excess ET | 2 | 1 | 8.1 | 1.10 | 1.03, 1.17 | 3 | 2 | 22.1 | 1.10 | 1.03, 1.17 | |
| ≥3 | 1 | 8.5 | 1.15 | 1.05, 1.26 | ≥4 | 2 | 21.9 | 1.02 | 0.92, 1.13 | ||
| Excess ET + FHB | ≥2 | ≥2 | 11.5 | 1.62 | 1.46, 1.80 | ≥3 | ≥3 | 25.8 | 1.31 | 1.18, 1.45 | |
| ET | FHB | % | AOR | 95% CI | ET | FHB | % | AOR | 95% CI | ||
| Low birthweight (<2500 g) | Reference | 1 | 1 | 7.2 | 1.00 | Reference | 2 | 2 | 54.7 | 1.00 | Reference |
| Excess ET | 2 | 1 | 8.4 | 1.09 | 1.02, 1.16 | 3 | 2 | 53.5 | 1.02 | 0.97, 1.07 | |
| ≥3 | 1 | 8.6 | 1.17 | 1.07, 1.27 | ≥4 | 2 | 55.9 | 1.16 | 1.07, 1.27 | ||
| Excess ET + FHB | ≥2 | ≥2 | 13.8 | 1.91 | 1.73, 2.11 | ≥3 | ≥3 | 63.0 | 1.52 | 1.39, 1.67 | |
| ET | FHB | % | AOR | 95% CI | ET | FHB | % | AOR | 95% CI | ||
| Preterm birth (≤36 weeks) | Reference | 1 | 1 | 9.9 | 1.00 | Reference | 2 | 2 | 59.5 | 1.00 | Reference |
| Excess ET | 2 | 1 | 11.4 | 1.06 | 1.00, 1.12 | 3 | 2 | 56.6 | 0.97 | 0.92, 1.02 | |
| ≥3 | 1 | 11.9 | 1.14 | 1.06, 1.23 | ≥4 | 2 | 58.9 | 1.16 | 1.07, 1.27 | ||
| Excess ET + FHB | ≥2 | ≥2 | 15.2 | 1.48 | 1.35, 1.62 | ≥3 | ≥3 | 62.3 | 1.27 | 1.16, 1.39 | |
| ET | FHB | % | AOR | 95% CI | ET | FHB | % | AOR | 95% CI | ||
| Early preterm birth (≤32 weeks) | Reference | 1 | 1 | 1.9 | 1.00 | Reference | 2 | 2 | 13.6 | 1.00 | Reference |
| Excess ET | 2 | 1 | 2.5 | 1.16 | 1.02, 1.31 | 3 | 2 | 12.5 | 1.00 | 0.92, 1.07 | |
| ≥3 | 1 | 2.4 | 1.18 | 1.01, 1.39 | ≥4 | 2 | 12.8 | 1.11 | 0.98, 1.25 | ||
| Excess ET + FHB | ≥2 | ≥2 | 4.4 | 2.10 | 1.78, 2.49 | ≥3 | ≥3 | 18.1 | 1.60 | 1.42, 1.79 | |
| ET | FHB | % | AOR | 95% CI | ET | FHB | % | AOR | 95% CI | ||
| Low birthweight (<2500 g) at term (≥37 weeks) | Reference | 1 | 1 | 2.2 | 1.00 | Reference | 2 | 2 | 23.9 | 1.00 | Reference |
| Excess ET | 2 | 1 | 2.5 | 1.03 | 0.91, 1.17 | 3 | 2 | 24.9 | 1.12 | 1.02, 1.22 | |
| ≥3 | 1 | 2.6 | 1.06 | 0.90, 1.26 | ≥4 | 2 | 25.0 | 1.12 | 0.96, 1.31 | ||
| Excess ET + FHB | ≥2 | ≥2 | 4.3 | 1.81 | 1.52, 2.17 | ≥3 | ≥3 | 28.7 | 1.35 | 1.15, 1.59 | |
Models adjusted for number of embryos transferred, number of fetal heartbeats, maternal age, race and Hispanic ethnicity, pregravid BMI, diabetes (pregestational and gestational), oocyte source and embryo state, infant sex, and State and year of birth
**Rate per 10,000 children
***Major defects limited to nonchromosomal only (major birth defects as defined by the National Birth Defects Prevention Network (NBDPN), see Supplemental Table 1)
Bolded values are significantly increased