Social class and human twinning

Abstract

In a comparative study to examine the effect of social factors on human twinning, data on sociodemographic and other factors were collected from parents of all twins born alive in Denmark in 1984 or 1985 and from a random sample of parents of singleton infants born in the same years. A postal questionnaire was used. The twins were classified as monozygotic (MZ) or dizygotic (DZ) twins by the similarity method. A trend was found in DZ-twinning, with significantly fewer DZ-twins born in the lower social classes, but not in MZ-twinning. All results were controlled for maternal age and parity.

Body composition, smoking, and spontaneous dizygotic twinning

“…Educational attainment did not alter the association of body composition and smoking before the twin pregnancy with DZ twinning. In fact, while both positive (28) and negative (1) associations have been reported for socioeconomic status and twinning, our study did not show any association between educational attainment and DZ twinning.…”

“…Smoking behavior and body composition are associated with socioeconomic status (22)(23)(24)(25)(26)(27), and socioeconomic status has been suggested to be associated with DZ twining (1,10,28), although the direction of the association is as yet unclear. We thus compared DZ twin mothers to MZ twin mothers for body composition and smoking before the twin pregnancy, after controlling for the effects of maternal age, gravidity, and educational attainment.…”

Secular Trend and Associated Factors of Twinning in Taiwan

“…The increase in DZ rates with maternal age has been consistently observed in many studies [1,3,5,12,14,22,24]. Our previous study also reported a slight increase of DZ rates with maternal age during the period 1975 to 1984 in Taiwan [7].…”

“…Many studies have reported on increased twinning rates associated with maternal age [1,3,5,12,14,22,24]. In Taiwan, both MZ and DZ rates increased with maternal age and parity in 1975-1984 [7].…”