In The Field

ASRM: Global boy shortage

IVF has many flaws, but a new one to me is that it skews the sex ratio. A lot. Normally in the US, just over 51% of babies born are boys and 49% are girls – and apparently there has been a worldwide trend in recent years towards fewer boys. (Is a global boy shortage approaching? Panic.)


Could IVF be contributing? The team at Montefiore Medical Center in Hartsdale, New York, found that only 41% of babies born after IVF were boys and 59% were girls, in their clinic at least.

The team suggests that stress during the procedure of IVF (which is intrinsically stressful) could prevent male embryos from implanting or surviving.

There have been various studies before showing that stressful situations tend to favour the birth of girls, such as war, earthquake, starvation. For some reason, male embryos are less likely to survive stress in the mother’s body. No doubt there is some evolutionary advantage to this that I am too ignorant to know about.

An aside. I’ve just realized that virtually everything I’ve written about has been from clinics in New York. Clearly it is some kind of reproductive biology research mecca.

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