Correlation Between Plasma Neurotransmitters and Memory Loss in Pregnancy

More than half of pregnant women believe that their memory becomes impaired, and, indeed, there is evidence from reported studies of objectively impaired memory function. One suggestion is that this is a result of abnormal tryptophan metabolism in pregnancy. The question of whether altered plasma levels of neurotransmitters might be responsible for pregnancy-related memory loss was addressed in 50 healthy pregnant women with an average age of 23, followed from the first trimester of pregnancy. Fifty nonpregnant women with an average age of 23 served as a control group. In addition to memory testing with the Wechsler memory scale, the participants were asked for personal information, tested for orientation, and completed tests requiring backward counting, reading and recalling a paragraph, writing digits forward and backward, and remembering photographs. The pregnant women had significant declines in plasma levels of epinephrine, serotonin, and dopamine in each trimester compared with control women. Plasma norepinephrine, in contrast, increased in the pregnant women. Memory declined significantly in each trimester, the deficit peaking in mid pregnancy. Functional memory correlated positively with levels of epinephrine, serotonin, and dopamine in the second trimester and negatively with plasma serotonin and dopamine levels in the third trimester. Norepinephrine and functional memory correlated negatively in all stages of pregnancy. Functional memory loss was most marked in the second trimester of pregnancy in these healthy women; the loss was minimal in late pregnancy. A decline in plasma neurotransmitter levels may be responsible. Studies of how well women remember parturition and of memory status in the postpartum period would be of interest.