Table 3. Pregnancy outcomes for underweight women in reference to weight gain.
| below | within | above | |||
|---|---|---|---|---|---|
| underweight | GWGa * *<12.5kg | GWG: 12.5-18kg | GWG>18kg | p-value* | |
| N = 13529 | N = 3783 | N = 412 | |||
| PIHb | |||||
| % (n) | 3.0% (n = 407) | 4.0% (n = 150) | 8.5% (n = 35) | <0.001 | |
| OR (95%CI) | 0.726 (0.594–0.887) | 1 | 2.380 (1.635–3.464) | ||
| GDMc | |||||
| % (n) | 3.0% (n = 405) | 1.6% (n = 61) | 1.5% (n = 6) | <0.001 | |
| OR (95%CI) | 1.703 (1.275–2.274) | 1 | 1.030 (0.476–2.229) | ||
| SGAd | |||||
| % (n) | 15% (n = 2032) | 5.6% (n = 23) | <0.001 | ||
| OR (95%CI) | 2.142 (1.849–2.482) | 7.6% (n = 286) | 0.774 (0.516–1.161) | ||
| LGAe | 1 | ||||
| % (n) | 3.8% (n = 518) | 10.3% (n = 388) | 14.8% (n = 61) | <0.001 | |
| OR (95%CI) | 0.352 (0.310–0.399) | 1 | 1.443 (1.067–1.950) | ||
| Preterm birth | |||||
| % (n) | 14.6% (n = 1979) | 4.4% (n = 167) | 1.9% (n = 8) | <0.001 | |
| OR (95%CI) | 3.857 (3.227–4.609) | 1 | 0.418 (0.202–0.869) | ||
| Spontaneous preterm birth | |||||
| % (n) | 12.2% (n = 1651) | 3.1% (n = 116) | 0.7% (n = 3) | <0.001 | |
| OR (95%CI) | 4.710 (3.805–5.830) | 1 | 0.226 (0.071–0.716) | ||
| PPROMf | |||||
| % (n) | 4.5% (n = 614) | 1.4% (n = 54) | 0.5% (n = 2) | <0.001 | |
| OR (95%CI) | 3.431 (2.526–4.661) | 1 | 0.319 (0.075–1.349) | ||
| Induced preterm birth | |||||
| % (n) | 2.4% (n = 328) | 1.4% (n = 51) | 1.2% (n = 5) | 0.003 | |
| OR (95%CI) | 1.619 (1.189–2.204) | 1 | 0.895 (0.354–2.260) | ||
| Total C/Sg | |||||
| % (n) | 23.5% (n = 3174) | 19.5% (n = 739) | 19.9% (n = 82) | 0.018 | |
| OR (95%CI) | 1.138 (1.037–1.247) | 1 | 1.205 (0.915–1.587) | ||
| PPHh with VDi | |||||
| % (n) | 18.2% (n = 2461) | 23.7% (n = 898) | 26.5% (n = 109) | <0.001 | |
| OR (95%CI) | 0.736 (0.675–0.803) | 1 | 1.081 (0.844–1.384) | ||
| PPH with C/S | |||||
| % (n) | 4.7% (n = 635) | 4.8% (n = 181) | 5.8% (n = 24) | 0.025 | |
| OR (95%CI) | 0.872 (0.728–1.043) | 1 | 1.453 (0.904–2.336) | ||
| macrosomia>4000g | |||||
| % (n) | 0.1% (n = 16) | 0.5% (n = 20) | 2.7% (n = 11) | <0.001 | |
| OR (95%CI) | 0.215 (0.118–0.392) | 1 | 5.292 (2.466–11.355) | ||
| post-term pregnancy | |||||
| % (n) | 0.16% (n = 21) | 0.16% (n = 6) | 0.24% (n = 1) | 0.925 | |
| ORj (95%CIk) | 0.998 (0.417–2.389) | 1 | 1.50 (0.186–12.113) | ||
aGWG, gestational weight gain, body mass index
bPIH, pregnancy-induced hypertension
c GDM, gestational diabetes mellitus
dSGA, small for gestational age
e LGA, large for gestational age
fPPROM, preterm prelabor rupture of membranes
gC/S,cesarian section
hPPH,postpartum hemorrhage
iVD,Vaginal delivery
jOR, odds ratio
kCI, confidence interval
* Logistic regression was used to adjust for confounding variables, including maternal age, maternal height and parity, and generalized estimating equations (GEE) for logistic regression was used to adjust for the clustering of deliveries by hospitals. The results were expressed as odds ratios (OR) and 95% confidence intervals (CI).
* * IOM Recommendation for gestational weight gain: underweight, 12.5–18 kg; normal, 11.5–16 kg; overweight, 7–11.5 kg; and obese, 5–9 kg.