Table 3.
Neonatal Outcomes by Maternal Age Category and Adjusted Odds Ratios
| Outcome | Younger Than 20.0 y (n = 19,638) | 20.0–24.9 y (n = 51,011) | 25.0–29.9 y (n = 56,480) | 30.0–34.9 y (n = 45,715) | 35.0–39.9 y (n = 24,351) | 40.0–44.9 y (n = 5,931) | 45.0 y or Older (n = 391) |
|---|---|---|---|---|---|---|---|
| Gestational age at delivery* (wk) | 38.5±2.7 | 38.6±2.4 | 38.6±2.2 | 38.5±2.3 | 38.4±2.5 | 38.2±2.6 | 38.1±2.7 |
| Birth weight* (g), (missing data = 2,340) | 3,091 (610) (n = 19,458) | 3,196 (596) (n = 50,373) | 3,271 (585) (n = 55,836) | 3,294 (606) (n = 45,202) | 3,282 (646) (n = 24,072) | 3,240 (678) (n = 5,851) | 3,202 (708) (n = 385) |
| Birth weight less than 1,500 g* (missing data = 2,340) | 521 (2.7) (n = 19,458) | 1,045 (2.1) (n = 50,373) | 920 (1.7) (n = 55,836) | 839 (1.9) (n = 45,202) | 571 (2.4) (n = 24,072) | 160 (2.7) (n = 5,851) | 12 (3.1) (n = 385) |
| OR | 0.95 | 0.99 | Referent | 1.17 | 1.39 | 1.53 | 1.98 |
| 99% CI | 0.79–1.14 | 0.86–1.14 | 1.01–1.36 | 1.18–1.65 | 1.17–2.01 | 0.87–4.51 | |
| Birth weight less than 2,500 g* (missing data = 2,340) | 2,343 (12.0) (n = 19,458) | 4,505 (8.9) (n = 50,373) | 4,009 (7.2) (n = 55,836) | 3,373 (7.5) (n = 45,202) | 2,069 (8.6) (n = 24,072) | 633 (10.8) (n = 5,851) | 53 (13.8) (n = 385) |
| OR | 1.13 | 1.03 | Referent | 1.08 | 1.24 | 1.52 | 2.19 |
| 99% CI | 1.03–1.24 | 0.96–1.11 | 1.00–1.16 | 1.13–1.35 | 1.32–1.75 | 1.41–3.38 | |
| Birth weight more than 4,000 g* (missing data = 2,340) | 736 (3.8) (n = 19,458) | 2,880 (5.7) (n = 50,373) | 4,223 (7.6) (n = 55,836) | 3,928 (8.7) (n = 45,202) | 2,264 (9.4) (n = 24,072) | 539 (9.2) (n = 5,851) | 35 (9.1) (n = 385) |
| OR | 0.63 | 0.84 | Referent | 1.11 | 1.22 | 1.18 | 1.24 |
| 99% CI | 0.55–0.72 | 0.78–0.91 | 1.04–1.19 | 1.12–1.33 | 1.02–1.36 | 0.75–2.05 | |
| Apgar score less than 7 at 5 min* (missing data = 996) | 459 (2.4) (n = 19,511) | 932 (1.8) (n = 50,765) | 847 (1.5) (n = 56,247) | 743 (1.6) (n = 45,505) | 505 (2.1) (n = 24,214) | 141 (2.4) (n = 5,890) | 10 (2.6) (n = 389) |
| OR | 1.00 | 0.97 | Referent | 1.11 | 1.32 | 1.48 | 1.39 |
| 99% CI | 0.82–1.21 | 0.83–1.12 | 0.96–1.30 | 1.10–1.57 | 1.12–1.97 | 0.51–3.78 | |
| NICU admission* | 2,768 (14.1) | 6,445 (12.6) | 6,500 (11.5) | 5,358 (11.7) | 3,190 (13.1) | 896 (15.1) | 70 (17.9) |
| OR | 0.98 | 0.99 | Referent | 1.07 | 1.21 | 1.47 | 1.81 |
| 99% CI | 0.91–1.06 | 0.93–1.05 | 1.01–1.13 | 1.13–1.30 | 1.30–1.65 | 1.24–2.66 | |
| NICU length of stay* median (d) | 7.1 (1.0, 52.0) | 7.0 (1.0, 48.0) | 6.4 (1.0, 44.0) | 7.0 (1.0, 47.0) | 7.0 (1.0, 48.0) | 8.0 (2.0, 52.0) | 7.0 (2.0, 49.0) |
| Stillbirth* | 118 (0.6) | 232 (0.5) | 214 (0.4) | 182 (0.4) | 138 (0.6) | 41 (0.7) | 5 (1.3) |
| OR | 1.31 | 1.01 | Referent | 1.07 | 1.47 | 1.66 | 2.35 |
| 99% CI | 0.89–1.92 | 0.74–1.36 | 0.78–1.45 | 1.04–2.07 | 0.97–2.85 | 0.51–10.80 | |
| Neonatal death* | 74 (0.4) | 182 (0.4) | 161 (0.3) | 153 (0.3) | 86 (0.4) | 26 (0.4) | 2 (0.5) |
| OR | 0.84 | 0.86 | Referent | 1.06 | 0.82 | 1.22 | 1.95 |
| 99% CI | 0.53–1.34 | 0.61–1.22 | 0.75–1.50 | 0.52–1.29 | 0.63–2.37 | 0.31–12.49 | |
| Perinatal mortality*† | 192 (1.0) | 414 (0.8) | 375 (0.7) | 335 (0.7) | 224 (0.9) | 67 (1.1) | 7 (1.8) |
| OR | 1.10 | 0.95 | Referent | 1.06 | 1.16 | 1.44 | 2.16 |
| 99% CI | 0.82–1.48 | 0.76–1.19 | 0.84–1.33 | 0.89–1.53 | 0.95–2.19 | 0.66–7.04 |
CI, confidence interval; OR, odds ratio; NICU, neonatal intensive care unit.
Data are mean±standard deviation, n (%), or median (10th, 90th percentiles) unless otherwise specified.
Adjusted odds ratios calculated from logistic regression and adjusted for maternal race, parity, body mass index, insurance type, pre-existing medical conditions, substance abuse, tobacco use, and reporting clinical site. The group aged 25.0–29.9 years was used as the referent category. Unless specified, missing data for logistic regression = 44,227.
*
P<.001.
†
Perinatal mortality defined as stillbirth and neonatal death.