Increasing evidence suggests a positive association between docosahexaenoic acid (DHA, 22:6n-3) and cognitive performance. In addition, pregnancy is associated with a reduction of the DHA status and cognitive deficits. In the current study, cognition was assessed in pregnant women receiving a margarine enriched with alpha-linolenic acid (ALA, 18:3n-3, the ultimate dietary precursor of DHA) and some linoleic acid (LA, 18:2n-6, to prevent a possible reduction in n-6 fatty acids). A control group received a margarine enriched with LA only. ALA supplementation hardly affected the maternal DHA status and no significant differences were found in cognitive performance between the two groups. This indicates that ALA supplementation during pregnancy does not affect cognitive performance during and 32 weeks after gestation. At week 14 of pregnancy and 32 weeks after delivery, higher plasma DHA levels were associated with lower cognitive performance as indicated by longer reaction times on the finger precuing task (partial correlation coefficients 0.3705 and 0.4633, respectively, P<0.01). Since this could imply an unexpected adverse association between DHA and certain aspects of cognitive functioning this certainly needs further investigation.