Pregnancy is the time when one or more  offspring occur in a woman's womb (pregnancy). Multiple pregnancies involve multiple children, including twins. Pregnancy is usually caused by  sexual intercourse, but it can  also be caused by assisted  reproductive technology. Pregnancy can end with childbirth, spontaneous abortion, miscarriage, or stillbirth. Birth usually occurs about 40 weeks after the start of the last menstrual period. This is a little over 9 months (gestational age). Using the age of fertilization, the duration  is about 38 weeks. Embryo is the term used for offspring that develop in the first 8 weeks after fertilization (ie (gestational age 10 weeks), after which term fetus is used until birth.

 Pregnancy is divided into three semesters, each about three months. The semesters involves conception when the sperm fertilize the egg. The fertilized egg then travel to the fallopian tubes and attaches to the inside of the uterus, where it begins to form embryo and placenta. During the first semesters the chance of miscarriage (natural death of an embryo or fetus) is highest. Fetal movement maybe felt in the middle of the second trimester. By 28 weeks, with quality medical care, more than 90% of babies can survive from the womb, but babies born at this point have heart and respiratory problems, long-term mental illness. You may have serious health problems such as disability.

Prenatal care improves pregnancy outcomes. Prenatal care may include folic acid suppliments, avoidance of drugs, smoking and alcohol, regular exercise, regular blood tests, and physical exams. Pregnancy complications can include high blood pressure disorders, gestational diabetes, iron deficiency anemia, and severe nausea and vomiting. In the ideal birth labour begins on its own when the woman is “full term". Babies born before 37 weeks are “premature” and are at increased risk for health problems such as cerebral palsy. Babies born between 37 and 39 weeks are considered “early”, while babies born between 41 and 42 weeks are considered “late birth” while after 42 weeks are considered “premature”. Delivery before 39 weeks by induction of labor or by cesarean section should not be given, unless necessary for other medical reasons.

In 2012, there were approximately 213 million pregnancies, 190 million (89%) in developing countries and 23 million (11%) in developed countries. The number of pregnancies for woman between the ages of 15 and 44 is 133 per 1,000 women. About 10% to 15% of approved pregnancies end with a miscarriage. In 2016, pregnancy complications resulted in 230,600 maternal mortality ratios from 377,000 deaths in 1990. Common causes include bleeding, infections, pregnancy hypertension, delivery disorders, miscarriage or ectopic pregnancy. Globally, 44% pregnancies are unplanned. More than half (56%) of unplanned pregnancies are completed. Among unintended pregnancies in the United State 60% of women used birth control to some extent during the month pregnancy began.