Table 3.
Association between fetal sex and delivery outcomes among women with live birth. (n = 897,426).
| Outcomes | Male (%) (n = 461,434) |
Female (%) (n = 435,992) |
Crude RR (95% CI) | Adjusted RRa (95% CI) |
|---|---|---|---|---|
| Categorized variables [n (%)] | ||||
| Preterm delivery (< 37 weeks) | 56,604 (12.27) | 44,476 (10.20) | 1.20 (1.19–1.22) | 1.20 (1.19–1.22) |
| Very preterm delivery (< 32 weeks) | 10,929 (2.37) | 9279 (2.13) | 1.11 (1.08–1.14) | 1.11 (1.08–1.14) |
| Extremely preterm delivery (< 28 weeks) | 3561 (0.77) | 3126 (0.72) | 1.08 (1.03–1.13) | 1.08 (1.02–1.13) |
| Macrosomia | 4575 (0.99) | 2369 (0.54) | 1.82 (1.74–1.92) | 1.83 (1.73–1.91) |
| Low birth weight | 67,151 (14.55) | 73,561 (16.87) | 0.84 (0.83–0.85) | 0.84 (0.83–0.85) |
| Non-cephalic position at birth | 24,715 (5.36) | 26,868 (6.16) | 0.87 (0.85–0.88) | 0.87 (0.85–0.88) |
| Hypotonic uterine inertia | 43,834 (9.50) | 38,753 (8.89) | 1.07 (1.05–1.08) | 1.07 (1.05–1.08) |
| Hypertonic uterine inertia | 512 (0.11) | 401 (0.09) | 1.21 (1.06–1.37) | 1.21 (1.06–1.37) |
| Atonic hemorrhage | 23,915 (5.18) | 23,869 (5.47) | 0.95 (0.93–0.96) | 0.95 (0.93–0.96) |
| Blood transfusion | 5032 (1.09) | 4983 (1.14) | 0.95 (0.92–0.99) | 0.95 (0.92–0.99) |
| Instrumental deliveryb | 36,260 (11.17) | 27,056 (8.79) | 1.27 (1.25–1.29) | 1.27 (1.26–1.29) |
| Cesarean delivery | 136,728 (29.63) | 128,039 (29.37) | 1.01 (1.00–1.02) | 1.01 (1.00–1.02) |
| Mean difference (95% CI) | Adjusted mean differencea (95% CI) | |||
|---|---|---|---|---|
| Continuous variables (mean ± SD) | ||||
| Gestational age at birth (weeks) | 38.1 ± 2.4 | 38.3 ± 2.35 | − 0.18 (− 0.19 to − 0.17) | − 0.18 (− 0.19 to − 0.17) |
| Birth weight (g) | 2934 ± 546 | 2857 ± 522 | 77.6 (75.4 to 79.8) | 77.3 (75.1 to 79.5) |
All risk ratios and mean differences are calculated with females set as the reference.
RR risk ratio, CI confidence interval, SD standard deviation.
aAdjusted for maternal age, maternal height, maternal pre-pregnant body mass index, parity, and maternal smoking status during pregnancy.
bAnalysis for instrumental delivery in 63,316 women (excludes those who received cesarean section).