The fusion of a haploid male gamete (spermatozoan) and a haploid female gamete (ovum) to form a diploid zygote is called fertilization. In human females, fertilization is internal and it takes place in the ampulla of the fallopian tube. Fertilization occurs within 6 hours after ovulation. The condition of carrying one or more embryos in the uterus is called Pregnancy or Gestation. Human pregnancy lasts for an average of 266 days from fertilization of the egg or 280 days from the start of the last menstrual cycle.