Table 3. Factors associated with anemia among pregnant women — 6 provinces in China, 2014–2018.

Variables	OR	95% CI	p value
Note: The six provinces (with the selected districts) are: Hebei (Xinhua and Zhengding), Liaoning (Lishan, Tiedong and Taian), Hunan (Yueyanglou and Yueyang), Fujian (Haicang and Jimei), Sichuan (Gongjing and Rong County) and Yunnan (Tonghai and Huaning). Taian stopped surveillance in 2016, so Tiedong County became the participant since then. Based on the economic development level and administrative divisions, Hebei and Liaoning provinces represented the northeast region, Hunan and Fujian provinces the central region, and Sichuan and Yunnan provinces the southwest region. In addition, pregnant woman were classified as natives or outsiders of the counties based on their census registration. Gestational week was based on the number of days between the first day of an expectant mother’s LMP and the date of antenatal examination. The first, second, and third trimester were defined as a gestational age less than 13 weeks, 13–27 weeks, and 28–42 weeks, respectively. Abreviation: ANC=antenatal care. OR=odds ratio. CI=Confidence interval.
Region
Central	Ref
Northeast	1.242	1.208–1.278	<0.001
Southwest	1.191	1.151–1.222	<0.001
Age (years)
<25	1.186	1.151–1.222
25–35	Ref		<0.001
≥35	0.93	0.894–0.967	<0.001
Education
Junior high or lower	Ref
Senior high	0.897	0.871–0.924	<0.001
University or above	0.842	0.818–0.867	<0.001
Parity
0	Ref
≥1	1.132	1.103–1.161	<0.001
Number of ANC examinations
<5	Ref
≥5	1.632	1.564–1.702	<0.001
Number of Hb tests
<3	Ref
≥3	3.289	3.192–3.388	<0.001
Trimester
First (<13 weeks)	Ref
Second (<28 weeks)	11.248	10.863–11.646	<0.001
Third (≥36 weeks)	47.220	45.530–48.973	<0.001