The main reason for this process is the spread of IVF methods, but other factors play a role as well.
On the increase in the number of births and the background of the phenomenon In the scientific journal NewScientist mentioned. Researchers at the University of Oxford examined birth data from 165 countries. Based on their findings, between 1980 and 2015, the birth rate with twins increased by a third worldwide. Previously, there were 9 out of every thousand births, and now there are 12.
Much of the growth is given by the bivalve twins, which develop from different eggs and sperm. The proportion of identical twins did not change during the observed period.
According to the researchers, the prevalence of IVF methods in high and middle income countries is the cause of this process. Treatments stimulate ovulation in women with hormones, which often causes two eggs to mature at the same time, giving them a better chance of giving birth to twins.
The proliferation of in vitro methods also increases the rate of twins. This occurs when fertilization takes place outside the body, and this is often called simply the baby’s vial procedure. In a single transplant, two to three or even more embryos can be implanted into the mothers’ uterus at the same time to increase the chances of at least one embryo surviving the operation. Often this process leads to the development of a twin pregnancy.
Since these pregnancies are likely to cause different complications, either premature labor or low birth weight, the new countries actually require only one embryo to be implanted in the mother during the operation. As a result of the new regulations, the number of twin pregnancies may start to decrease in the future.
However, it is not only IVF that is the reason behind the increase in the number of twins. It also plays a role in the fact that women in developed countries have children at a later time – and it is clear that older women are more likely to have two eggs at the same time.
Interestingly, Africa has traditionally had a higher incidence of bivalve twins at birth. Scientists believe that there may be unknown genetic reasons for this.
If we look at the Hungarian data, we also see that the proportion of twin births has increased dramatically, especially since the mid-1990s. The Central Statistical Office published its latest issue of births in 2014, which shows that by the 1990s, the proportion of births in Hungary was about 12 per thousand. Since then, however, it has grown rapidly, reaching 20 per thousand by 2010.
Consequently, the birth rate in Hungary is almost twice the global rate.
This also confirms that the global phenomenon is mostly due to the spread of IVF methods in the most developed countries.
Finally, there is an interesting fact, that births of triplets and twins are statistically described by Helen’s rule discovered in the nineteenth century. According to reviews, if N The number of single births is one twin births, then all N2 Aries is triple and everything N3 A twin birth of four. In practical terms, this means that if there are currently about twenty births in Hungary, every 60 births2That is, 3600 triple births, and every 60 births3That is, 216 thousand births for four successful births. The rule is confirmed by practice,
An average of 50 triplets are born in Hungary every year, and a total of 10 twins were born in Hungary between 2000 and 2019.
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