Claim: Pregnancy symptoms include missed periods.

Pregnancy , also known as gestation , is the time during which one or more offspring develops inside a woman . A multiple pregnancy involves more than one offspring , such as with twins . Pregnancy can occur by sexual intercourse or assisted reproductive technology . Childbirth typically occurs around 40 weeks from the last menstrual period -LRB- LMP -RRB- . This is just over nine lunar months , where each month is about 29 1/2 days . When measured from conception it is about 38 weeks . An embryo is the developing offspring during the first eight weeks following conception , after which , the term fetus is used until birth . Symptoms of early pregnancy may include missed periods , tender breasts , nausea and vomiting , hunger , and frequent urination . Pregnancy may be confirmed with a pregnancy test .   Pregnancy is typically divided into three trimesters . The first trimester is from week one through 12 and includes conception . Conception is when the sperm fertilizes the egg . The fertilized egg then travels down the fallopian tube and attaches to the inside of the uterus , where it begins to form the embryo and placenta . The first trimester carries the highest risk of miscarriage -LRB- natural death of embryo or fetus -RRB- . The second trimester is from week 13 through 28 . Around the middle of the second trimester , movement of the fetus may be felt . At 28 weeks , more than 90 % of babies can survive outside of the uterus if provided with high-quality medical care . The third trimester is from 29 weeks through 40 weeks .   Prenatal care improves pregnancy outcomes . Prenatal care may include taking extra folic acid , avoiding drugs and alcohol , regular exercise , blood tests , and regular physical examinations . Complications of pregnancy may include high blood pressure of pregnancy , gestational diabetes , iron-deficiency anemia , and severe nausea and vomiting among others . Term pregnancy is 37 to 41 weeks , with early term being 37 and 38 weeks , full term 39 and 40 weeks , and late term 41 weeks . After 41 weeks , it is known as post term . Babies born before 37 weeks are preterm and are at higher risk of health problems such as cerebral palsy . Delivery before 39 weeks by labor induction or caesarean section is not recommended unless required for other medical reasons .   About 213 million pregnancies occurred in 2012 , of which , 190 million were in the developing world and 23 million were in the developed world . The number of pregnancies in women ages 15 to 44 is 133 per 1,000 women . About 10 % to 15 % of recognized pregnancies end in miscarriage . In 2013 , complications of pregnancy resulted in 293,000 deaths , down from 377,000 deaths in 1990 . Common causes include maternal bleeding , complications of abortion , high blood pressure of pregnancy , maternal sepsis , and obstructed labor . Globally , 40 % of pregnancies are unplanned . Half of unplanned pregnancies are aborted . Among unintended pregnancies in the United States , 60 % of the women used birth control to some extent during the month pregnancy occurred .