The relation between gestational age at first antenatal visit and infa
nt's birth weight was investigated in a cohort study of 846 primiparas
living in the City of Dundee, Scotland, whose first antenatal visit w
as between 1 May 1985 and 30 April 1986. The earlier in pregnancy the
first antenatal visit the greater the infants' birth weights tended to
be (p < 0.01). The relation was independent of gestational age at bir
th, mother's age and height, social class, tobacco and alcohol consump
tion and the child's sex. The result supports similar findings elsewhe
re, but is more robust in that, in contrast to other studies, all birt
h weights were measured on a single electronic scale and the effects o
f maternal tobacco and alcohol consumption on birth weight were taken
into account in the analysis. The mechanism of the effect remains to b
e determined but needs to be identified as it may indicate possible pr
eventive measures for the benefit of future children.