From the moment of fertilisation until the 8th week of pregnancy, the developing human is called an embryo. First it divides into two cells; then they each divide again to give four cells, as on the diagram below:

Embryonic development and implantation

Implantation is the process by which a fertilised ovum implants in the thickened endometrium or uterine lining. It occurs 5-7 days after fertilisation.

If the embryo survives it is the beginning of pregnancy.

Implantation might occasionally occur in the fallopian tube, which is called ectopic pregnancy. This is dangerous for the woman. The tube may rupture as the embryo grows and cause severe pain and loss of blood.

If you suspect an ectopic pregnancy, refer the woman immediately to the nearest doctor or clinic