Twins occur in about one out of 90 human pregnancies in the US. As a rule, at conception, one sperm fertilizes a single egg to produce a zygote. Two thirds of twins are fraternal, with fertilization ...

Starting from some 60 years ago, bio-medical research into human conception has been extensive. The highly regarded British medical journal Lancet has, over the years, carried several articles on the ...

Until the 1930s physicians blithely told women that they conceived during menstruation and could avoid pregnancy by restricting coitus to other days. This, of course, conflicts directly with ...

From reproductive rights to climate change to Big Tech, The Independent is on the ground when the story is developing. Whether it's investigating the financials of Elon Musk's pro-Trump PAC or ...

New Haven, Conn. — In a common metaphor used to describe human fertilization, sperm cells are competitors racing to penetrate a passive egg. But as critics have noted, the description is also a “fairy ...

A study published this year in the Journal of Population Economics suggests climate change may result in lower rates of human conception. However, it’s not due to less sex, and it doesn’t necessarily ...

"Chimeras are the result of fusion of two zygotes to form a single embryo, producing an individual with genetically different kinds of tissue. If the fused zygotes are of different sex, the individual ...