Table 2.
Association between EPA+DHA concentrations and risk of early preterm birth. Shown are results for EPA+DHA measurements solely based on sample 1 (Panel A), solely based on sample 2 (Panel B), mean of sample 1 and 2 (Panel C), and mean of sample 1 and 2 after restricting the analysis to only comprise women in concordant quintiles across sample 1 and 2 (Panel D).
| Controls | Cases | Crude |
Adjusteda |
Controls | Cases | Further adjusted for 2nd//1st sample |
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|---|---|---|---|---|---|---|---|---|---|---|---|
| OR (95% CI) | P-Value | OR (95% CI) | P-Value | OR (95% CI) | P-Value | ||||||
| A: 1st trimester sample | |||||||||||
| Test for association in spline regression | – | <0.0001 | – | <0.0001 | – | <0.0001 | |||||
| Test for linear v. spline association | – | 0.0002 | – | 0.001 | – | 0.007 | |||||
| EPA+DHA categorized into quintiles | – | <0.0001 | – | <0.0001 | – | <0.0001 | |||||
| Q1: 0.37–1.48 | 67 | 192 | 5.54 (3.86; 8.02) | <0.0001 | 5.47 (3.72; 8.14) | <0.0001 | 66 | 186 | 3.62 (2.37; 5.58) | <0.0001 | |
| Q2: 1.48–1.81 | 67 | 71 | 2.05 (1.36; 3.09) | 0.0006 | 1.90 (1.23; 2.95) | 0.004 | 65 | 68 | 1.54 (0.95; 2.49) | 0.08 | |
| Q3-Q5: 1.81–4.74 | 199 | 103 | 1 | – | 1 | – | 196 | 102 | 1 | – | |
| B: 2nd trimester sample | |||||||||||
| Test for association in spline regression | – | <0.0001 | – | <0.0001 | – | <0.0001 | |||||
| Test for linear v. spline association | – | <0.0001 | – | <0.0001 | – | <0.0001 | |||||
| EPA+DHA categorized into quintiles | – | <0.0001 | – | <0.0001 | – | <0.0001 | |||||
| Q1: 0.47–1.42 | 68 | 226 | 9.33 (6.42; 13.74) | <0.0001 | 9.61 (6.46; 14.50) | <0.0001 | 66 | 220 | 7.41 (4.87; 11.42) | <0.0001 | |
| Q2: 1.43–1.74 | 69 | 67 | 2.73 (1.78; 4.20) | <0.0001 | 2.71 (1.72; 4.29) | <0.0001 | 66 | 65 | 2.51 (1.56; 4.07) | <0.0001 | |
| Q3-Q5: 1.74–4.95 | 205 | 73 | 1 | <0.0001 – |
1 | <0.0001 – |
195 | 71 | 1 | 0.0002 – |
|
| C: Mean of 1st and 2nd trimester samples | |||||||||||
| Test for association in spline regression | – | <0.0001 | – | <0.0001 | |||||||
| Test for linear v. spline association | – | <0.0001 | – | <0.0001 | |||||||
| EPA+DHA categorized into quintiles | – | <0.0001 | – | <0.0001 | |||||||
| Q1: 0.69–1.56 | 66 | 224 | 9.64 (6.58,14.31) | <0.0001 | 10.27 (6.80,15.79) | <0.0001 | |||||
| Q2: 1.56–1.82 | 65 | 63 | 2.75 (1.77,4.29) | <0.0001 | 2.86 (1.79,4.59) | <0.0001 | |||||
| Q3-Q5: 1.82–4.11 | 196 | 69 | 1 | – | 1 | – | |||||
| D: Mean of 1st and 2nd trimester samples: concordant quintiles only | |||||||||||
| Test for association in spline regression | – | <0.0001 | – | <0.0001 | |||||||
| Test for linear v. spline association | – | <0.0001 | – | <0.0001 | |||||||
| EPA+DHA categorized into concordant quintiles | – | <0.0001 | – | <0.0001 | |||||||
| Q1: | 1st: 0.37–1.48 2nd: 0.47–1.42 |
21 | 140 | 32.12 (15.03,74.33) | <0.0001 | 48.29 (20.18,128.99) | <0.0001 | ||||
| Q2: | 1st: 1.48–1.81 2nd: 1.43–1.74 |
18 | 18 | 4.82 (1.95,12.46) | <0.0001 | 6.42 (2.36,18.61) | <0.0001 | ||||
| Q3-Q5: | 1st: 1.81–4.74 2nd: 1.74–4.95 |
53 | 11 | 1 | – | 1 | – | ||||
| Q4: | 1st: 2.16–2.54 2nd: 2.05–2.45 |
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| Q5: | 1st: 2.55–4.74 2nd: 2.47–4.95 |
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In the covariate-adjusted analyses, maternal age at birth, maternal height, and maternal pre-pregnancy BMI were in all analyses modelled as restricted cubic splines with 3 knots at the 10th, 50th, and 90th percentiles, whereas parity, socioeconomic status (SES), cohabitation, residence, and smoking were categorized as in Table 1.
Adjusted for covariates: Maternal age at birth, maternal height, parity, maternal pre-pregnancy BMI, SES, cohabitation, residence and smoking.