Researchers from the University of Oxford announced that we are just breaking the record for the number of twins births, in most countries the largest number of twins are born since the start of registration. They base their claims on the analysis of data from 1980–85 and 2010–15 obtained from all over the world. It turns out that in the 80s, nine women out of a thousand gave birth to twins, now 12. The researchers see the reasons for this phenomenon primarily in the spread of medical assisted reproductive techniques (MAR), but this is not the only reason. So where did the flood of twins come from?
- The age at which women decide to become pregnant and the methods of medically assisted reproduction are responsible for the large number of twins
- Prof. Christiaan Monden: “Twin births are associated with higher infant and child mortality and more complications in mothers and children.”
- Most fraternal twins are born in Africa
- High Income Countries North America and Europe are currently at the peak of twin birth
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Every 42nd child is a twin
Scientists collected information from 165 countries, covering 99 percent. world population. For 112 countries, they obtained additional information from the 80s.
The numbers say that from the 80s to today, the percentage of twins has increased by a third, which means that about 1,6 million twins are born each year, i.e. every 42 babies are twins.
Medically assisted reproductive methods, which include in vitro fertilization (IVF), ovarian stimulation and artificial insemination, are the main reasons behind the increasing number of twins being born.
Besides, modern women delay the moment of getting pregnant. We know that the likelihood of having twins increases with age. The closer you are to menopause, the higher the chances that more than one egg will be released during ovulation.
Most twins in Asia and Africa
“The relative and absolute number of twins in the world has been growing since the mid-twentieth century,” says one of the authors of the study, Prof. Christiaan Monden. – This is important because twin births are associated with higher infant and child mortality and more complications in mothers and babies during pregnancy, and during and after birth.
About 80 percent. all twin births now take place in Asia and Africa. On the other hand, for example, in Great Britain, from 15 to 17 such births per thousand are registered – this is the global average.
In 74 percent. countries that shared data for both periods, the percentage of twin births increased by more than 10%. In Asia, there was an increase of 32%. and in North America by 71 percent. A decrease of over 10% recorded in only seven countries – Colombia, Ecuador, Venezuela, Angola, Congo, Gambia and Zambia.
– For Venezuela, the actual decline is likely to be less than 10%. – claims prof. Monden. – On the other hand, in African countries the indicators are rising again after a slight decrease.
Africa had the most twin births in both periods studied, but this is due to population growth. The twin birth rates are so high there thanks to the large number of fraternal twins. According to prof. Monden, this is due to genetic differences between the African population and other populations.
Scientists believe that high-income countries such as Europe and North America have already reached the peak of twin birth.
In vitro fertilization, known as IVF, is a medical procedure in which a fertilized egg is placed in the uterus. It is used when conception cannot occur naturally. The reproductive cells (sperm and egg) are taken from the pair and are combined in the laboratory. Once the embryo is established in the uterus, a pregnancy occurs and should proceed as normal.
The guidelines recommend IVF for women under the age of 43 who have been unsuccessfully two years trying to get pregnant through regular unprotected sex.
Professor Monden emphasizes that the transfer of two embryos into the uterus increases the likelihood of pregnancy and at the same time increases the chance of twins. Today, however, most parents and doctors emphasize conception of only one child through IVF. In many countries, fewer embryos are transferred than in the 90s and early XNUMXs.
If twins, then fraternal
Over the years, more fraternal twins have been born. The number of identical twins does not change and remains around the world at about four per thousand births.
The authors of the study suggest that the main cause of the increase in the birth of fraternal twins is the increasing availability and use of MAR. Medically assisted reproductive techniques began in the 70s. From wealthy western countries in the 80s and 90s, they spread to Asia and Latin America, and after 2000 to more prosperous parts of South Asia and Africa.
They depend on the age of the woman being treated and the cause of infertility (if known). Younger women are more likely to have a successful pregnancy. In vitro fertilization is usually not recommended for women over 42 as the chances of a successful pregnancy are too low.
In the years 2014 – 2016, the percentage of IVF procedures that ended in live birth was:
- 29 percent for women under 35 years of age
- 23 percent for women aged 35 – 37
- 15 percent for women aged 38 – 39
- 9 percent for women aged 40 – 42
- 3 percent for women aged 43 – 44
- 2 percent for women over 44 years of age
According to study co-author Professor Jeroen Smits of Radboud University in the Netherlands, although twin birth rates in many rich Western countries are now similar to those of Sub-Saharan Africa, their chances of survival vary greatly.
“As infant mortality decreases, the likelihood of twins growing up with a brother or sister increases,” says Prof. Smits. – Currently, the most attention should be paid to their fate in low and middle income countries. Especially in sub-Saharan Africa, many will lose their twin in the very first year of life. We estimate that around 200 to 300 annually.
See also:
- Why is “geriatric pregnancy” not a very happy term? Gynecologist: late motherhood is no longer a cause for shame
- How does female fertility change over the years? Doctor: There is a point where he is clearly falling
- From the “little stranger” to the fetus. How did doctors manage to “see” under the skin of mothers?
- To be a mom thanks to IVF
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