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Hellin's law, also called Hellin-Zeleny's law, is an empirical observation in demography that the approximate rate of multiple births is one n-tuple birth per 89 n-1 singleton births: twin births occur about once per 89 singleton births, triplets about once per 89 2, quadruplets about once per 89 3, and so on.
The power of twin designs arises from the fact that twins may be either identical (monozygotic (MZ), i.e. developing from a single fertilized egg and therefore sharing all of their polymorphic alleles) or fraternal (dizygotic (DZ), i.e. developing from two fertilized eggs and therefore sharing on average 50% of their alleles, the same level of genetic similarity found in non-twin siblings).
The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. [5] The Yoruba people have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, [6] [7] [8] possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may ...
In 2004, of the people younger than 35 who gave birth with the help of IVF, 32.7% delivered twins, and 4.9% delivered triplets, according to doctors at the Washington University School of Medicine ...
Twins are concordant when both have or both lack a given trait. [ 1 ] The ideal example of concordance is that of identical twins , because the genome is the same, an equivalence that helps in discovering causation via deconfounding , regarding genetic effects versus epigenetic and environmental effects ( nature versus nurture ).
Dizygotic (fraternal) twins can be caused by a hyperovulation gene in the mother. [8] Although the father's genes do not influence the woman's chances of having twins, he could influence his children's chances of having twins by passing on a copy of the hyperovulation gene to them. Monozygotic (identical) twins do not run in families.
After all, shortly after the fateful ultrasound, I discover that the odds of us having gotten spontaneously pregnant with twins, meaning without fertility assistance or genetic influence, were ...
And despite the world not even fully recovering from the exciting life update about baby Bieber no. 1, Justin's mom, Pattie Mallette, unknowingly started a rumor that the couple was having two!