CBSE Class 12-science Answered

Pregnancy occurs when a woman's egg joins with a man's sperm, a process called fertilisation. This usually happens inside the fallopian tube, which connects the ovary to the uterus. An embryo grows if the fertilised egg travels down the fallopian tube and implants in the uterus. 

Here are some steps that must occur for pregnancy to happen:

1. Sperm transport: The sperm must be deposited and transported to the site of fertilisation.
2. Egg transport: Ovulation must occur, and the egg must be "picked up" by the fallopian tube.
3. Fertilisation and embryo development: The sperm and egg must unite.
4. Implantation: The embryo must implant and begin to grow in the uterus.