Pregnancy occurs after the fertilization of the ova by the sperm. In a normal pregnancy, the baby develops naturally in the womb over a forty-week period. Some pregnancies result in multiple offspring (i.e., twins, triplets, etc.). One possible complication is an ectopic pregnancy. An ectopic pregnancy occurs when the fertilized egg implants in the fallopian tube instead of the uterus, which causes excruciating pain and may be life-threatening for the mother. Ectopic pregnancies usually have to be terminated to save the life of the mother. Pregnancy is divided into three trimesters, each with individual milestone developments for both the mother and the child. Over time, the fertilized egg develops into a zygote, then an embryo, and later a fetus. During pregnancy, a woman will receive prenatal care and attend pregnancy classes to help her understand the pregnancy, to prepare for motherhood, and to allow the doctor to monitor the development of the baby. Regular checkups also help identify potential complications and conditions both in the mother and the child so that they can be treated as soon as possible.