TABLE 4.
Combined effect of total vitamin A and vitamin D intake in pregnancy and RR estimates (95% CIs) for current asthma at age 7 y1
| Total vitamin A (RAEs/d) | Total vitamin D (µg/d) | Cases/total n | Prevalence, % | Crude RR | Adjusted RR2 |
|---|---|---|---|---|---|
| Low (≤2030) | Low (≤13.5) | 1687/41,903 | 4.0 | 1 (ref) | 1 (ref) |
| High (≥2031) | Low (≤13.5) | 381/7395 | 5.2 | 1.28 (1.15, 1.43) | 1.21 (1.08, 1.36) |
| Low (≤2030) | High (≥13.6) | 259/7427 | 3.5 | 0.87 (0.76, 0.98) | 0.86 (0.73, 1.00) |
| High (≥2031) | High (≥13.6) | 219/4951 | 4.4 | 1.10 (0.96, 1.26) | 0.99 (0.83, 1.18) |
1 n = 61,676. RRs are from a log binomial regression model. A high intake corresponds to the highest quintile (Q5) and low intake to all lower quintiles (Q1–Q4) in Table 3. Q, quintile; RAE, retinol activity equivalent; ref, reference.
2Adjusted for maternal total intake of vitamins A or D (mutual adjustment), vitamin E, vitamin C, folate, and sum of n–3 fatty acids (all in quintiles) and total energy intake (continuous); the following maternal prenatal factors: age at delivery (continuous), parity (0, 1, or ≥2), education (less than high school, high school, ≤4 y of college/university, or >4 y of college/university), prepregnancy BMI (kg/m2; <18.5, 18.5–24.9, 25.0–29.9, or ≥30), history of asthma (no or yes), history of atopy (no or yes), and smoking in pregnancy (no, quit, or yes); and the following mediators: birth weight (<2500, 2500–4500, or ≥4500 g) and prematurity (no or yes). Missing values in covariates were handled by multiple imputation (m = 10) by using chained equations.