The latter will cause the development of a male, the former of a female embryo.

It seems there is a uterine implant on the market, which can be used to selectively abort female embryos.

Changes in appearance of male and female embryos begin roughly eight weeks after conception.

Dr. Fagliano said there was no known biological difference between male and female embryos to explain the complete absence of male babies with cancer.

The bacteria are playing a numbers game, and they need to have a significant group of female embryos each generation.

Aristotle thought that female embryos developed more slowly than male embryos, but made up for lost time by developing more quickly after birth.

So we allow as many as thirty per cent of the female embryos to develop normally.

During the first 10 weeks of pregnancy, the external anatomy of male and female embryos appears to be identical.

For a few weeks, these chromosomes are all that differentiates male embryos from female embryos.

Alternatively, hormonal exposure in the womb may affect the character of the female's uterus, making it more hospitable to either male or female embryos.