title: Twinning frequencies in Baden-Wurttemberg according to maternal age and parity from 1955 to 1972.
abstract: The decline of the twinning rate in Germany since 1900 is exclusively due to a fall of the DZ rate. The analysis of the birth data in Baden-Württemberg from 1955 to 1972 shows that the decline of the DZ twinning rate can be explained only to a small extent by the shift of the maternal age-parity distribution towards younger mothers and lower parities. It appears reasonable that the greater part of this decline is caused by the lessening prevalence of the more fecundable, DZ twin-prone women due to the growing influence of family planning. Furthermore, it is imaginable that the probability for multiple ovulation is decreased after cessation of hormonal contraception.
mesh_terms: D003276:Contraceptives, Oral / Q000494:pharmacology; D005260:Female; D005298:Fertility / Q000187:drug effects; D005858:Germany; D006801:Humans; D008423:Maternal Age; D010298:Parity; D011247:Pregnancy; D014427:Twins; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic
chemical_list: D003276:Contraceptives, Oral