We did a follow-up study based upon a regional prescription register in Denmark. We identified all 435 women who in the period 1991-1996 had redeemed a prescription for CNS drugs during pregnancy. Among the rest of the pregnant women we randomly selected 1304 women who also had given birth to a child in the same region and period. We looked up the local health nurses Boel test results which were available for about 80%. Any abnormal test result was seen much more frequently among exposed (16%) than for not exposed (4%). The study has several limitations but raises concern that should be addressed in other and better designed studies.