Table 6.
Risks of adverse outcomes, infant morbidity, and infant mortality by maternal fertility group and plurality at birth: twins
| Very early preterm | Early preterm | Preterm | SGA | LGA | NICU | Neonatal | Infant | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Model #* | 22–27 weeks | 22–32 weeks | 22–36 weeks | (≤ − 1.28) | (≥ 1.28) | Admission | Death | Death | ||||||||||
| Infants | Model 1 | N | 75,565 | 75,565 | 75,565 | 150,628 | 150,628 | 79,104 | 152,939 | 152,939 | ||||||||
| Outcome | N, % | 2760 | 3.7% | 10,740 | 14.2% | 44,090 | 58.3% | 33,021 | 21.9% | 2585 | 1.7% | 25,421 | 32.1% | 1939 | 1.27% | 2506 | 1.64% | |
| Model 2 | N | 58,110 | 58,110 | 58,110 | 115,847 | 115,847 | 61,505 | 117,837 | 117,837 | |||||||||
| N, % | 1831 | 3.15% | 8105 | 14.0% | 34,530 | 59.4% | 24,086 | 20.8% | 2001 | 1.7% | 20,371 | 33.1% | 1122 | 0.95% | 1451 | 1.23% | ||
| AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | AOR | 95% CI | |||
| Fertility | Model 1 | Fertile | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Group | Subfertile | 1.77 | 1.44, 2.18 | 1.42 | 1.25, 1.61 | 1.14 | 1.04, 1.26 | 0.93 | 0.86, 1.01 | 0.94 | 0.74, 1.19 | 1.15 | 1.05, 1.26 | 1.40 | 1.08, 1.82 | 1.24 | 0.97, 1.57 | |
| IVF | 0.88 | 0.81, 0.97 | 0.97 | 0.92, 1.02 | 1.07 | 1.03, 1.11 | 1.02 | 0.99, 1.05 | 0.83 | 0.76, 0.91 | 1.13 | 1.08, 1.19 | 0.69 | 0.61, 0.78 | 0.67 | 0.61, 0.75 | ||
| IVF | Model 2 | Autologous, fresh | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Group | Autologous, thawed | 0.97 | 0.85, 1.12 | 1.01 | 0.94, 1.08 | 0.97 | 0.92, 1.02 | 0.60 | 0.57, 0.63 | 1.70 | 1.51, 1.91 | 0.96 | 0.90, 1.02 | 1.01 | 0.82, 1.24 | 0.97 | 0.81, 1.17 | |
| Donor, fresh | 0.89 | 0.74, 1.07 | 1.15 | 1.05, 1.26 | 1.20 | 1.12, 1.28 | 0.83 | 0.78, 0.87 | 1.25 | 1.06, 1.47 | 1.15 | 1.07, 1.24 | 0.93 | 0.71, 1.21 | 0.97 | 0.77, 1.22 | ||
| Donor, thawed | 1.12 | 0.83, 1.52 | 1.23 | 1.06, 1.42 | 1.35 | 1.21, 1.51 | 0.77 | 0.70, 0.85 | 1.32 | 1.02, 1.72 | 1.09 | 0.96, 1.23 | 0.87 | 0.56, 1.35 | 0.78 | 0.52, 1.16 | ||
| Co-morbidities | Model 1 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Hypertension | Pregestational | 1.29 | 1.00, 1.67 | 1.26 | 1.10, 1.46 | 2.29 | 2.02, 2.59 | 1.18 | 1.08, 1.30 | 0.93 | 0.70, 1.23 | 1.39 | 1.20, 1.61 | 0.78 | 0.53, 1.13 | 0.83 | 0.60, 1.16 | |
| Gestational | 0.45 | 0.37, 0.54 | 0.88 | 0.82, 0.95 | 2.29 | 2.15, 2.43 | 1.12 | 1.07, 1.17 | 1.05 | 0.91, 1.20 | 1.48 | 1.39, 1.57 | 0.56 | 0.43, 0.74 | 0.63 | 0.50, 0.79 | ||
| Model 2 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | |
| Pregestational | 0.51 | 0.41, 0.62 | 1.01 | 0.94, 1.09 | 2.62 | 2.46, 2.79 | 1.16 | 1.10, 1.22 | 0.86 | 0.74, 1.00 | 1.62 | 1.52, 1.72 | 0.53 | 0.39, 0.73 | 0.64 | 0.50, 0.83 | ||
| Gestational | 1.40 | 1.05, 1.87 | 1.37 | 1.17, 1.59 | 2.53 | 2.21, 2.90 | 1.25 | 1.12, 1.38 | 0.84 | 0.61, 1.14 | 1.46 | 1.25, 1.71 | 0.78 | 0.51, 1.19 | 0.83 | 0.57, 1.22 | ||
| Co-morbidities | Model 1 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Diabetes | Pregestational | 1.12 | 0.67, 1.87 | 1.58 | 1.23, 2.03 | 1.43 | 1.14, 1.79 | 0.96 | 0.80, 1.15 | 2.12 | 1.45, 3.11 | 1.58 | 1.28, 1.96 | 0.78 | 0.37, 1.66 | 1.05 | 0.58, 1.92 | |
| Gestational | 0.64 | 0.52, 0.79 | 1.04 | 0.95, 1.14 | 1.08 | 1.01, 1.16 | 0.92 | 0.87, 0.97 | 1.39 | 1.20, 1.61 | 1.22 | 1.14, 1.31 | 0.89 | 0.68, 1.16 | 0.86 | 0.69, 1.09 | ||
| Model 2 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | |
| Pregestational | 0.70 | 0.56, 0.88 | 1.05 | 0.96, 1.16 | 1.09 | 1.01, 1.17 | 0.93 | 0.88, 0.99 | 1.29 | 1.09, 1.52 | 1.28 | 1.19, 1.37 | 0.81 | 0.59, 1.10 | 0.80 | 0.61, 1.05 | ||
| Gestational | 1.06 | 0.53, 2.11 | 1.34 | 0.97, 1.84 | 1.15 | 0.89, 1.50 | 1.08 | 0.88, 1.34 | 1.76 | 1.06, 2.92 | 1.58 | 1.22, 2.05 | 2.22 | 1.03, 4.78 | 2.16 | 1.09, 4.28 | ||
| Length of | Model 1 | Term (≥37 weeks) | – | – | – | – | – | – | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference |
| Gestation | Preterm (<37 weeks) | – | – | – | – | – | – | 0.44 | 0.43, 0.46 | 1.89 | 1.70, 2.10 | 10.66 | 10.15, 11.19 | 2.64 | 1.98, 3.53 | 2.27 | 1.85, 2.79 | |
| Early Preterm (<32 weeks) | – | – | – | – | – | – | 0.22 | 0.21, 0.23 | 4.58 | 4.07, 5.16 | 74.42 | 69.06, 80.20 | 17.85 | 13.45, 23.68 | 13.68 | 11.14, 16.81 | ||
| Very early preterm (<28 weeks) | – | – | – | – | – | – | 0.21 | 0.19, 0.23 | 8.84 | 7.71, 10.14 | 51.95 | 46.91, 57.53 | 499.48 | 386.61, 645.30 | 299.74 | 248.67, 361.30 | ||
| Model 2 | Term (≥37 weeks) | – | – | – | – | – | – | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | |
| Preterm (<37 weeks) | – | – | – | – | – | – | 0.44 | 0.42, 0.45 | 1.86 | 1.65, 2.09 | 10.81 | 10.23, 11.42 | 2.79 | 1.93, 4.05 | 2.39 | 1.80, 3.17 | ||
| Early Preterm (<32 weeks) | – | – | – | – | – | – | 0.22 | 0.21, 0.24 | 3.96 | 3.45, 4.53 | 73.27 | 67.36, 79.70 | 22.27 | 15.57, 31.85 | 17.80 | 13.51, 23.45 | ||
| Very early preterm (<28 weeks) | – | – | – | – | – | – | 0.19 | 0.17, 0.21 | 8.64 | 7.37, 10.14 | 65.40 | 57.42, 74.48 | 540.5 | 387.13, 754.63 | 380.01 | 293.77, 491.55 | ||
| Placental | Model 1 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | – | – | – | – | – | – | – | – | – | – |
| Complications | Other excessive bleeding | 1.17 | 0.80, 1.70 | 1.20 | 0.97, 1.49 | 1.08 | 0.91, 1.28 | – | – | – | – | – | – | – | – | – | – | |
| Placenta previa | 0.75 | 0.36, 1.55 | 1.79 | 1.36, 2.37 | 3.48 | 2.56, 4.71 | – | – | – | – | – | – | – | – | – | – | ||
| Abruptio placenta | 5.79 | 4.52, 7.41 | 5.13 | 4.28, 6.16 | 3.61 | 2.85, 4.57 | – | – | – | – | – | – | – | – | – | – | ||
| Model 2 | None | 1.00 | Reference | 1.00 | Reference | 1.00 | Reference | – | – | – | – | – | – | – | – | – | – | |
| Other excessive bleeding | 0.71 | 0.43, 1.19 | 1.02 | 0.81, 1.29 | 0.95 | 0.79, 1.13 | – | – | – | – | – | – | – | – | – | – | ||
| Placenta previa | 0.94 | 0.49, 1.81 | 2.00 | 1.54, 2.60 | 3.63 | 2.69, 4.90 | – | – | – | – | – | – | – | – | – | – | ||
| Abruptio placenta | 6.84 | 5.21, 8.99 | 5.23 | 4.28, 6.38 | 3.21 | 2.50, 4.13 | – | – | – | – | – | – | – | – | – | – | ||
The N for the very early preterm, early preterm, and preterm outcomes is based on pregnancies, not infants. Models adjusted for maternal age, parity, hypertension and diabetes (pregestational and gestational), placental complications (placenta previa, abruptio placenta, and excessive bleeding), mode of delivery, infant sex, length of gestation, small-for-gestation birthweight, State of residence, year of birth, and fertility status. For model 1, the study population was categorized by fertility status as fertile (reference), subfertile, and IVF (limited to autologous-fresh cycles only); for model 2, the study population was limited to IVF-conceived pregnancies as autologous-fresh (reference), autologous-thawed, donor-fresh, donor-thawed. Italicized AORs and 95% CIs are increased; those that are additionally emphasized in bold are significantly increased