Model of a nude pregnant woman, computer artwork. Human pregnancy lasts for around 40 weeks. An egg cell (female reproductive cell) is fertilised by a sperm cell (male reproductive cell) and implants in the mother's uterus. The fertilised egg, or zygote, develops through stages called an embryo and a foetus, before it is born as a human baby. This woman is at an advanced stage of preganancy. Her abdomen has swollen to contain the developing child, and her breasts are swollen with the milk with which she will feed her baby.