When to start preconception nutrition

A large RCT (n=7,387) found that supplementation started 3+ months before conception improved birth outcomes more than starting in the first trimester. A separate trial (NiPPeR, n=1,729) showed enhanced preconception supplementation raised nutrient status within 1 month and cut late-pregnancy vitamin D insufficiency from 35% to 8.5%.

The practical takeaway: start a quality prenatal supplement as soon as you’re thinking about conceiving. The 3-month window aligns with the ~90 days of egg maturation, giving nutrients time to influence the eggs that will actually be ovulated.