Tobacco smoking and twinning.
In a case-control study an association was found between mothers' smoking habits and the frequency of dizygotic twinning. As cases were included all twins born in Denmark in 1984 and 1985. A random sample of 1.5% of mothers to singletons, born in the same period were selected as controls. Only live-borns, conceived after no hormonal treatment, were included in the study. The finding may be due to the well-known anti-estrogen effect of smoking.
Olsen
J
J
Institute of Social Medicine, University of Aarhus, Denmark.
Bønnelykke
B
B
Nielsen
J
J
D003430:Cross-Sectional Studies; D003718:Denmark; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D011247:Pregnancy; D011272:Pregnancy, Multiple; D012907:Smoking; D014427:Twins; D014429:Twins, Dizygotic