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Spearman correlations between the three periods of supplements use: week 13 to 17; week 9 to 12; week -4 to 8 (supplement use in four categories: no supplements; other supplements; folic acid only; folic acid plus), N=2911.
| Week 13 to 17 | Week 9 to 12 | Week -4 to 8 | |
|---|---|---|---|
| Week 13 to 17 | 1 | ||
| Week 9 to 12 | .459** | 1 | |
| Week -4 to 8 | .395** | .660** | 1 |
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