Pregnancy Symptoms: Pregnancy Overview

Pregnancy occurs when an egg is fertilized by a sperm, grows inside a woman's uterus (womb), and develops into a baby. In humans, this process takes about 264 days, but the obstetrician will date from the last menstrual period or 280 days (40 weeks).

The doctor will use certain terms in discussing a woman’s pregnancy. Some of the following definitions are useful:

Intra–uterine pregnancy: A normal pregnancy occurs when a fertilized egg is implanted in the uterus (womb) and an embryo grows.

Embryo: The term used for the developing fertilized egg during the first 12 weeks of pregnancy.

Fetus: The term used for the developing embryo after 12 weeks of gestation.

Beta human chorionic gonadotropin (also called beta–hCG): This hormone is secreted by the placenta and can be measured to determine the presence and progression of the pregnancy. Urine or blood can be tested for its presence, and it is the hormone measured by a home pregnancy test. A positive result means a woman is pregnant; however, this test result can stay positive for several weeks after delivering a baby or after a miscarriage.

Trimester: The length of time of a pregnancy is divided into three sections called trimesters (about three months each). Each trimester has particular events and developmental markers. For instance, the first trimester builds the foundation of the different organ systems.

Estimated date of delivery (EDD): The delivery date is estimated by counting forward 280 days from the first day of the woman’s last period. It is also called the estimated date of confinement (EDC).

The woman who is pregnant and her doctor will monitor the pregnancy either to prevent certain conditions from developing or to treat those conditions early. These conditions include the following:

High–risk pregnancy: If a woman is considered to be likely to have complications during pregnancy, the pregnancy may be termed high risk. Examples include pregnancies in women with diabetes and those with high blood pressure. Age–related complications can occur in women such as teenagers, women who are over the age of 35, or women who have been treated for infertility or with pregnancies from the use of assisted reproductive technologies.

Ectopic pregnancy: This is a pregnancy in which the egg implants somewhere other than the uterus. This can be life threatening. Ectopic pregnancy must be diagnosed early to avoid damage to the Fallopian tubes and to prevent serious illness or death. It is also called tubal pregnancy (if the egg implants in the Fallopian tubes) or extra–uterine pregnancy.

Cervical Incompetence or Preterm Labor: This is a condition in which the cervix begins to dilate (widen) and efface (thin) before the pregnancy has reached term. Cervical incompetence can be a cause of miscarriage and preterm birth in the second and third trimesters.

Preeclampsia/eclampsia: Preeclampsia is a systemic disease that can affect various organ systems. Vascular effects cause the blood pressure to rise in the woman who is pregnant, changes in kidney function, swelling throughout the body, and alterations in blood chemistry and nerve reflexes. If left untreated, preeclampsia can lead to eclampsia, a serious illness that causes seizures, coma, and even death.


Multiple Gestation (for example twins, triplets): Preterm birth is twice as likely in twin pregnancies as in singleton pregnancies. The percentage of preterm birth is even greater for triplet pregnancies and quadruplet pregnancies. Preeclampsia also occurs three to five times more frequently with multiple gestation.