Male and female reproductive systems allow human reproduction. Fertilisation occurs when a sperm and egg join to form an embryo. An embryo develops into an unborn baby in the uterus during pregnancy.

Each of those seven baby mice had two biological dads.

As more women have kids in their 40s ... It’s a grand experiment in human reproduction, and scientists don’t yet know what the result might be. So far, scientists have only scant evidence ...