Objective To study the level of 25-hydroxyvitamin D [25（OH）D] in women at the first and second trimesters of pregnancy in Shanghai,and to provide a reference for the supplement of vitamin D（Vit D） for pregnant women.Methods A total of 13 440 pregnant women [10 400 cases at the first trimester（<12 weeks） and 3 040 cases at the second trimester（12-27 weeks）] and 205 healthy subjects（healthy control group） were enrolled. The level of serum 25（OH）D was determined by enzyme-linked immunosorbent assay（ELISA）. Serum 25（OH）D levels <25,25-<50,50-<75,75-<250,250-375 and >375 nmol/L were as Vit D famine,deficiency,insufficiency,sufficiency overdose and poisoning. Results The level of serum 25（OH）D in healthy control group was（58.07±14.64） nmol/L,and the proportions of Vit D famine,deficiency,insufficiency and sufficiency were 1.95%（4 cases）,47.32%（97 cases）,41.95%（80 cases） and 8.78%（18 cases）,respectively. The level of serum 25（OH）D in pregnancy group was（45.05±15.79） nmol/L,and the proportions of Vit D famine,deficiency,insufficiency and sufficiency were 7.66%（1 029 cases）,55.69%（7 485 cases）,33.81%（4 544 cases） and 2.84%（382 cases）．The level of serum 25（OH）D in healthy control group was higher than that in pregnancy group（P<0.05）. The serum 25（OH）D levels at the first and second trimesters of pregnancy were（44.66±15.36） and（46.40±17.05） nmol/L. In the 2 groups,the proportions of Vit D famine were 7.72% and 7.43%,the proportions of deficiency were 56.67% and 52.34%,the proportions of insufficiency were 33.17% and 36.02%,and the proportions of sufficiency were 2.44% and 4.21%. The differences of Vit D deficiency,insufficiency and sufficiency proportions were significant statistically between the 2 groups（P<0.05）. The level of serum 25（OH）D in winter-spring [（44.27±15.98） nmol/L] was lower than that in summer-autumn [（45.76± 15.55） nmol/L]（P<0.01）. Conclusions The deficiency or insufficiency of Vit D is common in women at the first and second trimesters of pregnancy．The Vit D deficiency at the first trimester of pregnancy is more serious compared with that at the second trimester of pregnancy,which is more common in winter-spring. It would be good for pregnant women to have a determination of serum 25（OH）D at the first trimester of pregnancy,and the determination can provide a scientific and appropriate Vit D supplement.
