| Crude OR | p-value | Adjusteda OR | p-value | |
---|---|---|---|---|---|
Maternal Age | Less than 20 | 1.05 (0.96–1.15) | 0.216 | 1.02 (0.93–1.13) | 0.547 |
20 to 24 | 1.09 (1.03–1.15) | 0.001 | 1.07 (1.01–1.13) | 0.013 | |
25 to 29 | 1.0 (refb) | – | 1.0 (ref) | – | |
30 to 34 | 0.89 (0.84–0.93) | <  0.001 | 0.91 (0.87–0.96) | 0.001 | |
35 to 39 | 0.89 (0.84–0.95) | 0.001 | 0.91 (0.85–0.97) | 0.005 | |
Over 40 | 1.03 (0.93–1.14) | 0.512 | 1.04 (0.93–1.16) | 0.423 | |
Maternal Race/Ethnicity | NH Whitec | 1.0 (ref) | – | 1.0 (ref) | – |
NH Black | 0.52 (0.48–0.56) | <  0.001 | 0.47 (0.44–0.50) | <  0.001 | |
NH Asian | 0.69 (0.63–0.75) | <  0.001 | 0.79 (0.72–0.86) | <  0.001 | |
Hispanic | 0.87 (0.83–0.91) | <  0.001 | 0.80 (0.76–0.84) | <  0.001 | |
Others | 1.14 (1.04–1.26) | 0.004 | 1.02 (0.92–1.12) | 0.662 | |
Smoking before Pregnancy (Number of cigarettes per day) | No | 1.0 (ref) | – | 1.0 (ref) | – |
1–5 | 1.47 (1.32–1.64) | <  0.001 | 1.26 (1.12–1.41) | <  0.001 | |
6–10 | 1.68 (1.53–1.84) | <  0.001 | 1.37 (1.24–1.51) | <  0.001 | |
11–20 | 1.84 (1.68–2.01) | <  0.001 | 1.46 (1.33–1.60) | <  0.001 | |
> 20 | 1.67 (1.40–2.00) | <  0.001 | 1.42 (1.18–1.71) | <  0.001 | |
BMI | Underweight | 1.09 (0.97–1.22) | 0.118 | 1.01 (0.90–1.13) | 0.802 |
Normal | 1.0 (ref) | – | 1.0 (ref) | – | |
Overweight | 1.04 (0.99–1.09) | 0.062 | 1.06 (1.00–1.11) | 0.019 | |
Obesity I | 1.18 (1.12–1.25) | <  0.001 | 1.18 (1.12–1.25) | <  0.001 | |
Obesity II | 1.34 (1.25–1.44) | <  0.001 | 1.32 (1.23–1.42) | <  0.001 | |
Ex Obese d | 1.36 (1.26–1.48) | <  0.001 | 1.32 (1.21–1.43) | <  0.001 | |
Pre-pregnancy Diabetes | No | 1.0 (ref) | – | 1.0 (ref) | – |
Yes | 2.24 (1.97–2.55) | <  0.001 | 1.96 (1.71–2.25) | <  0.001 | |
Pre-pregnancy Hypertension | No | 1.0 (ref) | – | 1.0 (ref) | – |
Yes | 1.31 (1.17–1.47) | <  0.001 | 1.17 (1.04–1.31) | 0.009 | |
Previous Preterm Birth | No | 1.0 (ref) | – | 1.0 (ref) | – |
Yes | 1.46 (1.34–1.59) | <  0.001 | 1.41 (1.29–1.54) | <  0.001 | |
Infertility Treatment Use | No Treatment | 1.0 (ref) | – | 1.0 (ref) | – |
Fertility Enhancing Drugs | 0.92 (0.72–1.18) | 0.562 | 0.96 (0.75–1.24) | 0.800 | |
Asst. Reproductive Technology | 1.27 (1.08–1.49) | 0.003 | 1.40 (1.18–1.66) | <  0.001 | |
Both | 1.35 (0.89–2.03) | 0.146 | 1.39 (0.90–2.17) | 0.134 |