Table 4.
Early Pregnancy Body Mass Index and Risk of Early-onset Neonatal Sepsis Stratified by Gestational Age at Delivery
| Early-onset Neonatal Sepsis | |||||
|---|---|---|---|---|---|
| Gestational Age at Delivery | No. of Infantsa | No. | Risk/1000 Live Births | Unadjusted HR (95% CI)b | Adjusted HR (95% CI)c |
| Term delivery (≥37 weeks) | |||||
| Maternal BMI,d kg/m2 | |||||
| <18.5 | 41 825 | 24 | 0.57 | 0.88 (.59–1.32) | 0.87 (.57–1.32) |
| 18.5–24.9 | 1 047 447 | 682 | 0.65 | 1.00 | 1.00 |
| 25.0–29.9 | 424 635 | 362 | 0.85 | 1.31 (1.15–1.49) | 1.37 (1.20–1.56) |
| 30.0–34.9 | 140 072 | 157 | 1.12 | 1.72 (1.45–2.05) | 1.86 (1.55–2.22) |
| 35.0–39.9 | 42 357 | 64 | 1.51 | 2.32 (1.79–3.01) | 2.59 (1.99–3.37) |
| ≥40.0 | 14 712 | 24 | 1.63 | 2.51 (1.67–3.77) | 2.82 (1.87–4.24) |
| Missing | 164 770 | 117 | 0.71 | ||
| P, trende | <.0001 | <.0001 | |||
| Per 1 kg/m2 | 1.06 (1.05–1.07) | 1.06 (1.05–1.07) | |||
| Per 10 kg/m2 f | 1.68 (1.53–1.84) | 1.79 (1.62–1.97) | |||
| Moderately preterm delivery (32–36 weeks) | |||||
| Maternal BMI, kg/m2 | |||||
| <18.5 | 2385 | 10 | 4.19 | 1.09 (.58–2.06) | 1.13 (.59–2.14) |
| 18.5–24.9 | 42 072 | 162 | 3.85 | 1.00 | 1.00 |
| 25.0–29.9 | 18 100 | 55 | 3.04 | 0.79 (.58–1.07) | 0.81 (.59–1.10) |
| 30.0–34.9 | 6733 | 26 | 3.86 | 1.00 (.66–1.52) | 0.98 (.63–1.52) |
| 35.0–39.9 | 2367 | 17 | 7.18 | 1.87 (1.13–3.07) | 1.86 (1.10–3.15) |
| ≥40.0 | 881 | 5 | 5.68 | 1.47 (.61–3.58) | 1.60 (.66–3.92) |
| Missing | 9630 | 45 | 4.67 | ||
| P, trend | .30 | .32 | |||
| Per 1 kg/m2 | 1.01 (.99–1.04) | 1.01 (.99–1.04) | |||
| Per 10 kg/m2 | 1.11 (.87–1.41) | 1.12 (.87–1.44) | |||
| Very preterm delivery (28–31 weeks) | |||||
| Maternal BMI, kg/m2 | |||||
| <18.5 | 212 | 12 | 56.60 | 1.16 (.66–2.04) | 1.26 (.71–2.22) |
| 18.5–24.9 | 4030 | 197 | 48.88 | 1.00 | 1.00 |
| 25.0–29.9 | 1853 | 79 | 42.63 | 0.87 (.68–1.13) | 0.87 (.67–1.13) |
| 30.0–34.9 | 799 | 43 | 53.82 | 1.10 (.80–1.52) | 1.06 (.76–1.47) |
| 35.0–39.9 | 283 | 11 | 38.87 | 0.80 (.44–1.44) | 0.80 (.44–1.46) |
| ≥40.0 | 138 | 6 | 43.48 | 0.89 (.40–1.97) | 0.93 (.42–2.05) |
| Missing | 1459 | 84 | 57.57 | ||
| P, trend | .56 | .51 | |||
| Per 1 kg/m2 | 0.99 (.97–1.01) | 0.99 (.97–1.01) | |||
| Per 10 kg/m2 | 0.94 (.78–1.14) | 0.92 (.76–1.13) | |||
| Extremely preterm delivery (22–27 weeks) | |||||
| Maternal BMI, kg/m2 | |||||
| <18.5 | 83 | 12 | 144.58 | 0.90 (.53–1.54) | 1.00 (.59–1.70) |
| 18.5–24.9 | 1789 | 286 | 159.87 | 1.00 | 1.00 |
| 25.0–29.9 | 890 | 140 | 157.30 | 0.98 (.82–1.19) | 0.98 (.81–1.19) |
| 30.0–34.9 | 398 | 79 | 198.49 | 1.24 (.99–1.56) | 1.12 (.88–1.41) |
| 35.0–39.9 | 144 | 18 | 125.00 | 0.78 (.50–1.22) | 0.78 (.50–1.22) |
| ≥40.0 | 75 | 10 | 133.33 | 0.83 (.46–1.50) | 0.89 (.50–1.59) |
| Missing | 1207 | 186 | 154.10 | ||
| P, trend | .87 | .72 | |||
| Per 1 kg/m2 | 1.00 (.99–1.02) | 1.00 (.98–1.01) | |||
| Per 10 kg/m2 | 1.02 (.89–1.16) | 0.98 (.85–1.13) | |||
Abbreviations: BMI, body mass index CI, confidence interval; HR, hazard ratio.
aLive-born singleton infants in Sweden 1997–2016.
bFrom Cox proportional hazards models with day of hospital admission for sepsis as the outcome.
cHRs and 95% CIs from Cox proportional hazards models with robust estimates of variance. The outcome was day of hospital admission for sepsis. Covariates included maternal age, country of origin, education level, cohabitation with a partner, parity, height, smoking during pregnancy, and year of delivery. Complete case analyses per category included 1277 cases among 1 662 647 full-term infants, 265 cases among 70 239 moderately preterm infants, 335 cases among 7015 very preterm infants, and 513 cases among 3206 extremely preterm infants.
dBMI calculated as weight in kilograms divided by height in meters squared.
eWald test when a variable representing ordinal categories of BMI was introduced into a Cox proportional hazards model as a continuous predictor.
fTen units is the difference in median BMI of women with obesity (32.8 kg/m2) and without obesity (23.1 kg/m2).