Baena de Moraes M H, Beiguelman B, Krieger H
Department of Medical Genetics, School of Medicine, UNICAMP, Campinas.
Acta Genet Med Gemellol (Roma). 1989;38(1-2):57-63. doi: 10.1017/s000156600000283x.
The twinning rate during a twenty-year period (1965-1985) was investigated at five-year intervals in four Brazilian hospitals. During this period the twinning rate has decreased significantly (from 10.68% to 8.11%), being highly negatively correlated with the five-year intervals (r = -0.97). This change was due mainly to the decline in dizygotic twinning, since the incidence of DZ twins has fallen from around 7% in 1965 to around 3.6% in 1985. The detected decline in DZ twinning seems to be due to the remotion of the fertility advantage of the more fecundable DZ twin-prone women by the introduction of effective birth control at the present, while some other mechanisms are causing the decline irrespective of the type of twinning.
在巴西的四家医院，每隔五年对二十年期间（1965 - 1985年）的双胎率进行调查。在此期间，双胎率显著下降（从10.68%降至8.11%），与五年间隔呈高度负相关（r = -0.97）。这种变化主要是由于双卵双胎率的下降，因为双卵双胎的发生率已从1965年的约7%降至1985年的约3.6%。检测到的双卵双胎率下降似乎是由于目前引入有效的节育措施消除了更易受孕的双卵双胎倾向女性的生育优势，而其他一些机制也在导致双胎率下降，与双胎类型无关。
