Table 3.

Multivariable logistic regression and multilevel regression analyses

Maternal weights	Test IDA				Composite IDA
	aOR (95% CI)	P	Multilevel aOR (95% CI)	P	aOR (95% CI)	P	Multilevel aOR (95% CI)	P
Prepregnancy BMI
Underweight	1.33 (1.15–1.53)	<0.001	1.35 (1.17–1.57)	<0.001	1.31 (1.17–1.45)	<0.001	1.35 (1.21–1.51)	<0.001
Overweight	0.65 (0.52–0.81)	<0.001	0.68 (0.54–0.86)	0.001	0.80 (0.69–0.92)	0.002	0.77 (0.67–0.90)	0.001
Obese	0.27 (0.12–0.63)	0.002	0.30 (0.13–0.69)	0.005	0.36 (0.22–0.57)	<0.001	0.34 (0.21–0.55)	<0.001
Rate of GWG (kg/week)	1.76 (1.21–2.57)	0.003	1.86 (1.26–2.76)	0.002	1.55 (1.18–2.03)	0.002	1.54 (1.16–2.03)	0.003

We adjusted the following confounders: Maternal age (<35 vs. ≥35 years), maternal race (Han vs. others), education (≥17 vs. 13–16 vs. 10–12 vs. ≤9 years), local citizens (yes vs. no), area of residence (urban vs. rural), annual family income (<30,000 vs. 30,000–79,999 vs. 80,000–119,999 vs. 120,000–199,999 vs. ≥200,000 CNY), multiple gestations (yes and no), parity (<1 vs. ≥1), gestational week at the survey first versus second versus third trimester, defined as <13⁺⁶, 14–27⁺⁶ and ≥28 gestational week, egg intake per week (unit of 0.5 kg), meat intake per week (unit of 0.5 kg), active or passive smoking (yes vs. no), nausea and/or vomiting during pregnancy (no vs. slight vs. severe), multivitamins supplement (yes vs. no), calcium supplement (yes vs. no), and multiple gestational comorbidities including hepatitis B, cardiovascular diseases, gynecological diseases, diabetes mellitus (not including gestational diabetes), thyroid disease, diseases of immune system and digestive system (yes vs. no, respectively). IDA: Iron deficiency anemia; aOR: Adjusted odds ratio; CI: Confidence interval; BMI: Body mass index; GWG: Gestational weight gain.