OBJECTIVE: There have been indications that high intake of n-3 long-chain polyunsaturated fatty acids (PUFAs) during pregnancy may increase birth weight and gestational length. In addition, n-3 long-chain PUFAs may be important for the neurobiological development of the infants. High levels of docosahexaenoic acid (DHA, 22:6 n-3) are found in the gray matter of the cerebral cortex and in the retina, and it seems as if the availability of long-chain PUFAs may be limiting cerebral development. The fetus and the newborn are dependent on a high supply from their mothers, either via the placenta or via breast milk. We supplemented pregnant and lactating women with n-3 or n-6 long-chain PUFAs to evaluate the effect on birth weight, gestational length, and infant development.

DESIGN: We performed a double-blind, randomized study recruiting 590 pregnant, healthy, nulli- or primiparous women (19-35 years old) in weeks 17 to 19 of pregnancy. The women were provided 10 mL of either cod liver oil or corn oil daily until 3 months after delivery.

MAIN OUTCOME MEASURES: Primary outcomes were gestational length and birth weight. Electroencephalography (EEG) was done on the second day of life and at 3 months of age. Novelty preference (Fagan test) was used as an indicator of cognitive function at 6 and 9 months of age. The fatty acid pattern in umbilical plasma phospholipids and in breast milk was measured, and dietary assessments were performed, both on the mothers during pregnancy and on the infants at 3 months of age. The growth of the infants was followed up to 1 year of age.

RESULTS: Three hundred forty-one mothers took part in the study until delivery. There were no significant differences in maternal body mass index before pregnancy and at birth, or parity between the 2 groups. Smoking habits and parental education were also similar in the 2 groups. The mean age of the mothers receiving cod liver oil was, by chance, 1 year higher than the age of the mothers receiving corn oil (28.6 [3.4] vs 27.6 [3.2] years). The maternal dietary intake in the 2 groups receiving cod liver oil or corn oil was similar, except for the supplementation. There were no differences in gestational length or birth weight between the cod liver oil group and the corn oil group (279.6 [9.2] vs 279.2 [9.3] days; 3609 [493] vs 3618 [527] g, respectively). Birth length, head circumference, and placental weight were also similar in the 2 groups. The concentrations of the n-3 fatty acids eicosapentaenoic acid (20:5 n-3), docosapentaenoic acid (22:5 n-3), and DHA in umbilical plasma phospholipids were higher in the cod liver oil group compared with the corn oil group (10.8 [7.6] vs 2.5 [1.8] microg/mL, 5.0 [2.6] vs 2.9 [1.3] microg/mL, 55.8 [20.6] vs 45.3 [12.8] microg/mL, respectively).

Neonates with high concentration of DHA in umbilical plasma phospholipids (upper quartile) had longer gestational length than neonates with low concentration (lower quartile; 282.5 [8.5] vs 275.4 [9.3] days). No differences in EEG scores or Fagan scores were found, but neonates with mature EEG (N = 70) had a higher concentration of DHA in umbilical plasma phospholipids than neonates with immature EEG (N = 51) on the second day of life. Dietary information from 251 infants at 3 months of age was collected and 85% of these infants were exclusively breastfed, in addition to 12% who were partly breastfed. The breast milk of mothers supplemented with cod liver oil contained more n-3 long-chain PUFAs and less n-6 long-chain PUFAs than breast milk of mothers supplemented with corn oil. There were no significant differences in infant growth during the first year of life between the 2 groups.

CONCLUSIONS: This study shows neither harmful nor beneficial effects of maternal supplementation of long-chain n-3 PUFAs regarding pregnancy outcome, cognitive development, or growth, as compared with supplementation with n-6 fatty acids. However, it confirms that DHA concentration may be related to gestational length and cerebral maturation of the newborn.