The impact of large Y chromosome on pregnancy, foetus and birth.

In a current investigation of children born in the Arhus area (Denmark) chromosome examinations were made in 6,691 newborns. Of these children, 170 boys had a large Y chromosome (2.6%). The present material was examined using a bi-variate stratified analysis to eliminate social and simple biological factors that could act as confounders. No increased frequency of malformations was found, and birth weight and length was nearly equal in the probands and the controls. A significantly increased frequency of prostaglandin stimulation of labour was found for the mothers of the Yq+ boys. Differences in the frequency of mechanical disproportion or abnormal presentation could not explain this. The Yq+ boys suffered more frequently from intrauterine asphyxia leading to acute Caesarean section. This finding cannot be explained by long-standing placenta problems alone. A possible mechanism which could link these findings together is suggested, and it is concluded that the boys with Yq+ most probably should be regarded as being at a certain risk at the time of birth.