Table 3. Plasma concentrations of vitamin D during pregnancy and after birth.
Data are presented in mean and standard deviation (SD).
| Sampling occasion | 1 | 2 | 3 | 4 | 5 | |||||
|---|---|---|---|---|---|---|---|---|---|---|
| (n = 183) | P | (n = 179) | p | (n = 174) | p | (n = 155) | p | (n = 145) | p | |
| Gestational week/weeks after birth | 12 | 21 | 35 | 12 | 29 | |||||
| Concentration of 25(OH) D (nmol/L) (mean (SD)) | ||||||||||
| Both seasons together | 55.2 (17.5) | 60.2 (22.5) | 64.6 (27.3) | 54.2 (16.4) | 53.5 (16.6) | |||||
| Season1 (winter) | 51.4 (16.9) | 50.2 (17.2) | 57.4 (25.4) | 52.6 (17.4) | 49.4 (16.8) | |||||
| Season1 (summer) | 62.8 (6.2) | <0.001 | 69.6 (23.0) | <0.001 | 73.1 (27.1) | <0.001 | 57.2 (13.8) | 0.093 | 59.0 (14.8) | <0.001 |
| Multipara | 53.6 (16.2) | 0.559 | 55.9 (21.8) | 0.048 | 61.8 (27.4) | 0.293 | 54.3 (17.5) | 0.950 | 51.0 (15.5) | |
| Nullipara | 56.1 (18.2) | 62.7 (22.6) | 66.3 (27.2) | 54.1 (15.8) | 55.0 (17.1) | |||||
| Multivitamin supplement latest year (no)2 | 54.1 (19.1) | 60.0 (23.3) | 61.6 (27.7) | 52.8 (16.1) | 52.7 (16.0) | |||||
| Multivitamin supplement latest year (yes)2 | 56.6 (15.2) | 0.347 | 60.4 (21.7) | 0.892 | 67.9 (26.7) | 0.129 | 55.9 (16.7) | 0.244 | 54.5 (17.2) | 0.515 |
| Multivitamin supplement latest 14 days (no)2 | 52.9 (19.1) | 58.7 (22.9) | 63.8 (29.4) | 52.8 (16.4) | 51.9 (16.4) | |||||
| Multivitamin supplement latest 14 days (yes)2 | 58.4 (14.2) | 0.027 | 62.9 (21.7) | 0.222 | 66.0 (23.7) | 0.591 | 59.5 (15.5) | 0.040 | 61.0 (15.2) | 0.010 |
| Education (< university) | 55.9 (17.1) | 61.9 (22.0) | 63.9 (26.5) | 54.4 (17.0) | 53.3 (15.9) | |||||
| Education (university) | 54.7 (17.8) | 0.660 | 59.0 (22.8) | 0.395 | 65.1 (27.9) | 0.765 | 54.0 (16.0) | 0.892 | 53.7 (17.0) | 0.892 |
| Age (≤34 years) | 55.5 (17.8) | 59.9 (22.4) | 63.8 (27.8) | 54.7 (16.6) | 53.0 (16.9) | |||||
| Age (≥ 35 years) | 53.5 (16.0) | 0.559 | 61.7 (23.3) | 0.680 | 68.7 (24.8) | 0.367 | 51.8 (15.7) | 0.370 | 55.3 (15.4) | 0.472 |
| Dietary intake of vitamin D (μg/day)3 | 5.1 (1.9) | 5.0 (2.0) | 4.9 (1.8) | 5.4 (2.1) | 5.3 (2.4) | |||||
| Vitamin D with supplement latest year μg/d)3 | 12.6 (1.8) | 12.4 (1.9) | 12.4 (1.7) | 13.2 (2.0) | 13.0 (2.4) | |||||
| Vitamin D with supplement latest 14 days (μg/d)3 | 12.5 (1.7) | 12.5 (1.9) | 12.6 (1.6) | 13.3 (1.9) | 13.7 (3.1) |
p = Differences between groups within each time point (column) are tested with Student’s t-test.
1 Summer; April 15 –September 15, Winter; September 16 –April 14 [11].
2 Mean values represent estimated nutrient intake with addition from supplements in those who reported intake of multivitamin the latest year or 14 days. Addition has been done with the most common content in over-the-counter sold supplement targeting women at the time of blood sampling measurement, i.e. vitamin D 7.5 μg.
3 Nutrient intake increased by 25% to adjust for underreporting resulting from shortening of the FFQ by 25% from the original validated version [17].