Pregnancy, also known as gestation, is the period where a woman carries a baby in her body. A multiple pregnancy involves more than one baby, such as with twins. Pregnancy can occur by sexual intercourse or assisted reproductive technology called In Vitro Fertilization (IVF).

Pregnancy usually lasts about 40 weeks from the last menstrual period (LMP) and ends in childbirth. When measured from conception it is about 38 weeks.

Symptoms of early pregnancy may include missed periods, tender breasts, nausea and vomiting, back pain, hunger, and frequent urination. Pregnancy may be confirmed by visiting a doctor or testing with a pregnancy kit.

The developing baby in a pregnant woman is called different terms at different development stage. The baby is called an embryo during the first eight weeks following conception and subsequently the term fetus is used until birth.

Pregnancy is divided into three trimesters. The first trimester, which includes conception, is from the week 1 to 12 . Conception is when the sperm fertilizes the egg. The fertilized egg then travels down the fallopian tube and attaches itself to the inside of the uterus. It will begin to form the fetus and placenta. The first trimester has the highest risk of miscarriage where natural death of embryo or fetus may occur.

The second trimester is from week 13 through 28. The movement of the fetus may be felt at around the middle of the second trimester. More than 90% of babies can survive outside of the uterus at week 28 if provided high quality medical care.

The third trimester is from week 29 through week 40.