For every 100 girls 107 boys are born worldwide. At fertilization, the number of boys and girls alike, however. Until now, scientists thought that even just after fertilization were more male than female embryos. But that turns out to be wrong. Girls and boys start in equal numbers, but in the pregnancy of a girl is greater risk of miscarriage, according to a study by the Fresh Pond Research Institute in Cambridge, US .
Steven Hecht Orzack and his colleagues examined a large set of US data on fetuses at different times during pregnancy. Including embryos that originated from artificial insemination or in vitro fertilization, data on abortions, flakes tests and amniocentesis (which always is a risk of miscarriage), and dates of death and live births.
Analysis of all the data showed that there are many boys as girls ‘made’. But the male embryos appear to be for more genetic defects, so more male than female embryos are divested during the first week after conception. Those early miscarriages are actually quite normal: about half of the fertilized eggs spontaneously emitted before the woman in question knows that she is pregnant
then boys are the stronger sex.. Because during the next ten to fifteen weeks ending more pregnancies of girls than of boys in a miscarriage. By the end of pregnancy (between week 28 and week 35) are then more boys born dead.
We look at the entire pregnancy, than die more female than male embryos, concludes Orzack. Leaving some at birth slightly more boys. In the US are born for every 100 girls 105 boys – in Belgium and the Netherlands are the same figures. Worldwide is about 107 boys – to make that possible with higher numbers of abortions (unwanted) girl babies. In China, for example, be there for every hundred girls 112 to 119 boys born. (Bw)
The study is published in the journal PNAS .
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