Sufficient maternal dietary intake of n-3 fatty acids (FA) supports offspring development. We aimed to construct simple criteria for dietary counselling to improve intake of n-3 FA.

Serum phospholipid FA from mothers and infants were analysed by GC one month after delivery. Dietary intake of foods during pregnancy and one month after delivery were recorded using 3 d food diaries and an index for healthy eating was calculated. Fish consumption was established by questionnaires. Dietary consumption of foods resulting in an increase in serum n-3 FA was defined.

A mother–child follow-up study in Southwest Finland.

Mothers (n 90) and 1-month-old infants (n 63).

After delivery, the mother’s consumption of fish at least three times per week resulted in an increase in total serum n-3 FA (mean difference (95 % CI): 1·7 (0·7, 2·8) % of total FA, P<0·001) and DHA (1·1 (0·5, 1·8) % of total FA, P<0·001) compared with non-consumers. Persistent fish intake once weekly throughout pregnancy increased total serum n-3 FA (P=0·001) and DHA (P<0·001). Overall, a healthy diet (middle and highest tertiles of healthy eating index score v. the lowest tertile) resulted in higher total serum n-3 FA (P=0·004) and DHA (P=0·008). Mother’s diet along with higher serum levels of n-3 FA were related to serum FA levels in 1-month-old infants.

An overall healthy diet and persistent consumption of fish at least once weekly throughout pregnancy or more frequent fish intake three times per week increases n-3 FA in serum phospholipids of both mothers and their infants.