Table 2. Influence of maternal characteristics on serum zinc level during pregnancy.

Characteristics	n	Maternal serum zinc (μg/dL, means ± SD)	P
Maternal age (y)
≤24	507	92.8 ± 37.8	0.141
25–29	2000	90.2 ± 27.3
≥30	680	92.0 ± 31.4
Monthly incomea
Low	1464	90.5 ± 29.0	0.431
Middle	1661	91.3 ± 31.0
High	62	94.9 ± 29.6
BMIb (kg/m2)
<18.5	682	88.2 ± 28.6*	0.019
18.5–24.9	2314	91.7 ± 30.0
≥25	191	92.8 ± 35.7
Parity
1	3056	91.1 ± 29.9	0.251
≥2	131	88.0 ± 35.4
Gravidity
1	1661	91.1 ± 30.1	0.768
≥2	1526	90.8 ± 30.1

^aLow income for <2000 RMB per month; middle income for ≥2000 RMB per month; high income for ≥4000 RMB per month.

^bPre-pregnancy BMI.

^*P < 0.01 as compared with normal BMI (18.5–24.9 kg/m²).