Defining an Ectopic Pregnancy
The initial goal of every normal pregnancy is for an embryo to implant inside a woman’s uterus. An ectopic pregnancy is defined as a pregnancy located in any other location than the upper portion of the uterus. Currently, the incidence of ectopic pregnancies is 2% of spontaneous conceptions, increasing to 5% from pregnancies established through assisted reproductive technology (ART) and 6-8% with a history of a tubal surgery or a prior ectopic.
Over 80% of ectopic pregnancies occur in the fallopian tube, with the remainder found in the cornu (opening to the fallopian tubes) of the uterus, the cervix, the ovary, and even the abdominal cavity (1% of ectopic pregnancies). A much more rare event is a heterotopic pregnancy defined as two embryo implantations simultaneously occurring in the uterus and an ectopic location. The incidence of a heterotopic pregnancy is 1 in 10,000 spontaneous conceptions but dramatically increases to 1% of pregnancies occurring through ART.
Produced from placenta tissue of the early embryo, hCG (human chorionic gonadotropin) can provide clues to the healthy development and even location of a pregnancy. Blood levels for this pregnancy hormone, hCG, normally rise at a minimum slightly greater than 50% in 48 hours. While 15% of normal pregnancies may demonstrate an abnormal rate of hCG rise, 15% of abnormal or ectopic pregnancies may show a normal rate of rise. Transvaginal ultrasound (TVUS) should visualize a pregnancy inside a woman’s uterus when the hCG level is above 2000 mIU/mL, otherwise an ectopic pregnancy should be strongly suspected, but exceptions occur. Further, a woman with an ectopic pregnancy may also present with vaginal bleeding, abdominal pain, and TVUS revealing a mass outside the uterus, with or without cardiac activity, and fluid inside her abdomen internal hemorrhage.
For centuries, the diagnosis of ectopic pregnancy carried a very high mortality rate that unfortunately remains in third world countries today. Over the course of the 20th century, advances in the detection of hCG and improvements in ultrasound visualization, particularly TVUS, allowed the treatment of ectopic pregnancy to transition from life-saving to fertility-saving.
Traditional treatment has been surgical for removal of the affected tube via opening the woman’s abdomen. Advances in laparoscopy have reduced the invasiveness of tubal surgery to a same day procedure. Depending on the degree of damage to the affected tube, the surgeon may be able to spare the tube, however, there is a risk of a persistent presence of ectopic pregnancy tissue in up to 20% of cases that may require methotrexate therapy (see below).
Outcome for future fertility depends on the condition of the other fallopian tube. When the unaffected tube is normal, subsequent ongoing pregnancy rates are the same, approximately 60%, whether the treatment is “tubal-sparing” (salpingostomy) or “tubal removing” (salpingectomy).
Since the early 1990s, a cancer chemotherapy drug injection, methotrexate, has been used to treat a woman with ectopic pregnancy diagnosed in the early stages with effectiveness approximately 90%, particularly with lower levels of hCG.
To conclude, an ectopic pregnancy remains a life threatening condition with improved survival and fertility rates due to early detection.
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