Pregnancy is the term used to describe the period in which a fetus develops inside a woman’s womb or uterus. Pregnancy usually lasts about 40 weeks, or just over 9 months, as measured from the last menstrual period to delivery. Health care providers refer to three segments of pregnancy, called trimesters. The major events in each trimester are described below.
First Trimester (Week 1 to Week 12)
The events that lead to pregnancy begin with conception, in which a sperm penetrates an egg. The fertilized egg (called a zygote) then travels through the woman’s fallopian tube to the uterus, where it implants itself in the uterine wall. The zygote is made up of a cluster of cells that later form the fetus and the placenta. The placenta connects the mother to the fetus and provides nutrients and oxygen to the fetus.
Second Trimester (Week 13 to Week 28)
Third Trimester (Week 29 to Week 40)
The most common early signs and symptoms of pregnancy might include:
Other less obvious signs and symptoms of pregnancy that you might experience during the first trimester include: