Table 2.
Neonatal characteristics according to maternal pre-pregnancy BMI and postpartum vitamin D status
| Characteristic1 | All | 25(OH)D < 50 nmol/L | 25(OH)D ≥ 50 nmol/L | P-value2 | ||||
|---|---|---|---|---|---|---|---|---|
| BMI < 25 kg/m2 (n = 24) | BMI ≥ 25 kg/m2 (n = 21) | BMI < 25 kg/m2 (n = 69) | BMI ≥ 25 kg/m2 (n = 28) | 25(OH)D | BMI | 25(OH)D*BMI | ||
| Birth | ||||||||
| Gestational age, wk | 39.64 (39.5, 39.8) | 39.9 (39.4, 40.4) | 39.7 (39.2, 40.1) | 39.7 (39.4, 39.9) | 39.3 (38.9, 39.8) | 0.13 | 0.13 | 0.90 |
| Sex, n (%) | ||||||||
| Male | 83 (58.5) | 13 (54.2) | 14 (66.7) | 40 (58.0) | 16 (57.1) | 0.002 | 0.01 | 0.04 |
| Female | 59 (41.5) | 11 (45.8) | 7 (33.3) | 29 (42.0) | 12 (42.9) | 0.003 | 0.01 | 0.47 |
| UVB period3, n (%) | ||||||||
| Synthesizing | 83 (58.5) | 14 (58.3) | 9 (42.9) | 43 (62.3) | 17 (60.7) | < 0.0001 | 0.001 | 0.34 |
| Non-synthesizing | 59 (41.5) | 10 (41.7) | 12 (57.1) | 26 (37.7) | 11 (39.3) | 0.05 | 0.09 | 0.06 |
| Weight, kg | 3.4 (3.3, 3.5) | 3.4 (3.3, 3.6) | 3.5 (3.3, 3.7) | 3.3 (3.3, 3.4) | 3.4 (3.2, 3.6) | 0.12 | 0.44 | 0.69 |
| Weight z score | 0.2 (0.0, 0.3) | 0.3 (−0.1, 0.7) | 0.3 (− 0.1, 0.7) | 0.1 (− 0.1, 0.2) | 0.2 (− 0.1, 0.5) | 0.20 | 0.68 | 0.54 |
| Serum 25(OH)D, nmol/L | 44.5 (41.3, 47.6) | 29.3 (24.8, 33.7) | 26.6 (23.0, 30.2) | 54.3 (50.0, 58.6) | 46.7 (40.8, 52.5) | < 0.0001 | 0.07 | 0.38 |
| Postnatal visit | ||||||||
| Age, mo | 0.7 (0.6, 0.8) | 0.7 (0.6, 0.8) | 0.6 (0.5, 0.8) | 0.7 (0.7, 0.8) | 0.7 (0.6, 0.8) | 0.37 | 0.25 | 0.51 |
| Weight, kg | 4.0 (3.9, 4.1) | 4.1 (3.8, 4.3) | 3.9 (3.7, 4.2) | 3.9 (3.8, 4.1) | 4.0 (3.8, 4.2) | 0.61 | 0.68 | 0.29 |
| Weight z score | −0.1 (− 0.2, 0.0) | 0.1 (−2.0, 0.5) | − 0.01 (− 0.4, 0.4) | −0.2 (− 0.4, − 0.03) | −0.02 (− 0.4, 0.3) | 0.23 | 0.86 | 0.28 |
| Length, cm | 53.1 (52.7, 53.4) | 53.8 (52.9, 54.8) | 53.0 (52.2, 53.8) | 52.9 (52.4, 53.3) | 53.0 (52.1, 53.9) | 0.22 | 0.34 | 0.19 |
| Length z score | −0.01 (− 0.2, 0.1) | 0.4 (− 0.1, 0.8) | 0.1 (− 0.3, 0.4) | −0.2 (− 0.4, 0.1) | −0.03 (− 0.4, 0.3) | 0.06 | 0.57 | 0.20 |
| Head circumference, cm | 36.4 (36.2, 36.6) | 36.5 (35.9, 37.0) | 36.5 (35.9, 37.0) | 36.3 (36.1, 36.6) | 36.7 (36.2, 37.2) | 0.95 | 0.40 | 0.43 |
| Head circumference z score | 0.1 (−0.02, 0.3) | 0.2 (− 0.3, 0.6) | 0.3 (− 0.1, 0.7) | −0.03 (− 0.2, 0.2) | 0.3 (0.01, 0.7) | 0.71 | 0.13 | 0.43 |
| Serum 25(OH)D, nmol/L | 54.7 (51.9, 57.5) | 45.1 (40.3, 49.9) | 42.3 (34.5, 50.1) | 61.9 (57.9, 65.9) | 54.5 (49.3, 59.7) | < 0.0001 | 0.08 | 0.42 |
| Skin tone4, n (%) | ||||||||
| F I-III | 110 (77.5) | 17 (70.8) | 14 (66.7) | 59 (85.5) | 20 (71.4) | < 0.0001 | < 0.0001 | 0.04 |
| F IV-VI | 32 (22.5) | 7 (29.2) | 7 (33.3) | 10 (14.5) | 8 (28.6) | 0.48 | 0.72 | 0.75 |
Abbreviations: 25(OH)D 25-hydroxyvitamin D, F Fitzpatrick, UVB Ultraviolet B
1Data are mean (lower and upper 95% confidence limits) or n (%)
2Data were compared using a linear fixed effect model for continuous variables followed by post hoc Tukey’s tests with Tukey-Kramer adjustment for multiple comparisons; and Chi-square or Fisher exact tests for categorical variables (using frequency procedure to create 3-way cross tabulation tables; categorical variables were used in the model to stratify the crosstabulation tables followed by the last two variables: maternal 25(OH)D*pre-pregnancy BMI, creating two 2-way tables of 25(OH)D and pre-pregnancy BMI, for each level of the categorical variables)
3Vitamin D synthesizing: April 1st-October 31st or vitamin D non-synthesizing: November 1st-March 31st
4Classified based on Fitzpatrick descriptions: F I-III (light) and F IV-VI (dark) [30, 31]