What Is an Intrauterine Pregnancy?

Overview
An intrauterine pregnancy is a “normal” pregnancy. That is, a fertilized egg implants itself in the wall of the uterus, where the placenta can develop and the fetus can grow. Fertilized eggs that implant themselves elsewhere, such as in the fallopian tubes, can cause a life-threatening emergency.

Significance
In the normal course of human fertilization, an egg is pushed out of the ovary into the fallopian tube, which leads to the uterus. During its transit in the fallopian tube, the egg encounters sperm cells, and fertilization may occur. The fertilized egg continues its journey down the tube to the uterus, where it eventually embeds in the wall of the uterus, or endometrium. The pregnancy then continues from that point: The placenta grows from the endometrium to nourish the embryo, which then develops into a fetus.

Effects
An intrauterine pregnancy is a “normal” human pregnancy. If all goes well, a baby will arrive in approximately 9 months.

Types
Occasionally, a fertilized egg implants itself somewhere other than the wall of the uterus. Implantation may occur on the wall of the fallopian tube itself. This is sometimes called a tubal pregnancy. Less often, the fertilized egg may lodge on the cervix, on the outer surface of the ovary or even somewhere in the abdomen. An implantation that occurs anywhere but the wall of the uterus is called an ectopic pregnancy, a pregnancy outside the uterus or an abnormal implantation.

Identification
A missed period is often the first signal to a woman that she is pregnant. A home pregnancy test can tell you if you’re pregnant about the time that you expect your next period. Pregnancy tests assess levels of a hormone called human chorionic gonadotropin (hCG), which increases extremely rapidly during early pregnancy. How rapidly? The amount of hCG doubles every few days.

Warning
About one in 50 pregnancies is an ectopic pregnancy. If the fertilized egg has implanted itself in the fallopian tube, which is the most common ectopic scenario, the tube will eventually rupture in response to the growth of the embryo. The outcome is always fatal for the embryo in this circumstance, and the bleeding that follows threatens the life of the woman. This is a medical emergency. You should seek help if you are in the early (first 8 weeks) of pregnancy and notice vaginal bleeding; fainting pain on one side of the abdomen; cramping, pain in the neck, back or rectum; or nausea. A trans-vaginal or abdominal ultrasound conducted at this time can precisely locate the site of the embryo. If your blood tests indicate that you’re pregnant but there’s no visual evidence of pregnancy during the ultrasound, ectopic pregnancy becomes more likely. Your doctor will perform a pelvic exam to check for unusual tenderness in the area of the uterus and fallopian tubes. If the uterus is smaller than expected for the stage of pregnancy, this may also suggest an ectopic pregnancy.

If you are having an ectopic pregnancy, surgery will be necessary to stop the bleeding and removed the damaged tissue. Any woman can have an ectopic pregnancy, but women who have had a previous one or who have had fertility treatments are at higher risk than other women.