Vitamin D status in early pregancy / 中华临床营养杂志

ABSTRACT

Objective To investigate the serum 25-hydroxy vitamin D concentrations and related factors in early pregnancy. Methods Plasma was collected in the first trimester from 23 396 pregnant women to inves-tigate the vitamin D level, and its distribution and differences in different age, body maxx index ( BMI) and seasons between primipara and multipara. Preterm birth was used as an indicator of clinical outcomes. Vitamin D concentrations were measured using chemiluminescence microparticle immunoassay. Results 25-hydroxy vi-tamin D level was 42. 0 (17. 6-76. 6) nmol/L in totally 23 396 pregnant women with early pregnancy, and 5% and 95% percentile sites of vitamin D level were 20. 2 nmol/L and 70. 7 nmol/L respectively. There were 18 170 (77. 7%) primiparas and 5 226 (22. 3%) multiparas, with the mean age of 30. 0 (24. 0-38. 0) years and BMI of 20. 7 (16. 5-27. 6) kg/m2. The number of cases detected in spring (March, April and May), summer (June, July and August), autumn (September, October and November months) and winter (Decem-ber, January and February) were 5 878, 5 554, 5 974, and 5 990, respectively, and the vitamin D levels were 40. 0 (29. 3, 52. 7) nmol/L, 46. 2 (35. 6, 57. 2) nmol/L, 43. 8 (33. 1, 54. 8) nmol/L and 37. 2 (26. 9, 49. 9) nmol/L respectively, with the difference in vitamin D levels statistically significant among the four seasons (P<0. 001). According to BMI, all pregnant women were divided into four groups as BMI<18. 5 kg/m2, 18. 5 kg/m2≤BMI≤23. 9 kg/m2, 24 kg/m2≤BMI≤27. 9 kg/m2, BMI≥28 kg/m2, and the levels of 25-hydroxy vitamin D were 43. 5 (30. 9, 56. 9) nmol/L, 42. 1 (30. 8, 53. 8) nmol/L, 39. 9 (30. 7, 50. 4) nmol/L and 39. 7 (30. 7, 49. 4) nmol/L respectively with the difference statistically significant among the four groups. The levels of vitamin D detected in pregnant women with age<25 years, 25~29 years, 30~34 years,≥35 years were 39. 1 ( 28. 4, 52. 3) nmol/L, 41. 3 ( 30. 1, 52. 9) nmol/L, 42. 4 ( 31. 2, 54. 1) nmol/L and 43. 8 (31. 9, 55. 7) nmol/L respectively and the difference was statistically significant (P<0. 001). The levels of 25-hydroxy vitamin D in primary and multiparas were 41. 6 (30. 2, 52. 9) nmol/L and 43. 5 (32. 5, 56. 8) nmol/L with the difference statistically significant (P<0. 001). Among women of different gestational age during childbirth, the differences in serum 25-hydroxy vitamin D in early pregnancy were not statistically significant (P=0. 121). The severe deficiency of vitamin D in early pregnancy was defined as serum level of 25-hydroxy vita-min D less than 5th level. There were statistical differences in the probability of severe vitamin D deficiency of dif-ferent ages, seasons and BMI between primiparas and multiparas. Conclusions Pregnant women of lower weight, lower age and primiparity have higher incidence of the severe vitamin D deficiency in early trimester of pregnancy. There is significant difference in 25-hydroxy vitamin D level among the different seasons (winter<spring<autumn<summer). Vitamin D level in early pregnancy is not associated with preterm birth.