There is some connection between human chorionic gonadotropin (HCG) levels and ectopic pregnancy. One of the ways a doctor can detect an ectopic pregnancy is by testing the levels of HCG, a hormone produced during pregnancy, in a woman's blood. When blood tests are done and the HCG levels appear lower than normal or are declining, this can sometimes be a sign of an ectopic pregnancy. HCG levels can even be used to assess whether or not a pregnancy may be ectopic by ultrasound; If the HCG levels reach a certain minimum threshold and an ultrasound does not reveal the expected signs of a uterine pregnancy, this is a sign that the pregnancy may be ectopic.
In a normal, healthy, early pregnancy, HCG levels generally rise steadily; in most cases, they double every two to three days. To determine if a pregnancy is healthy and viable, doctors often perform blood tests to assess HCG levels. If the HCG levels are not as high as expected for the pregnancy stage, doctors may order repeat blood tests. These blood tests are used to check if a woman's HCG levels continue to rise and double as expected. Since there is a connection between HCG levels and ectopic pregnancy, low or decreasing levels in these repeat HCG tests generally mean that further evaluation is necessary.
Doctors generally do not rely on the connection between HCG levels and ectopic pregnancy alone to determine whether or not a woman has a pregnancy in a fallopian tube. Instead, doctors can perform an ultrasound once the levels have reached 2,000 milli-international units per milliliter to check for a developing pregnancy in utero. Its absence sometimes, but not always, signifies an ectopic pregnancy. Pelvic exams and other tests may be done to confirm a diagnosis.
While there is a connection between HCG levels and ectopic pregnancy, low, slow, and declining HCG levels do not always indicate an ectopic pregnancy. Sometimes low HCG levels can simply mean that a pregnancy is not as advanced as originally thought. Slow-to-rise levels may even indicate that a pregnancy is more advanced than expected, as HCG levels generally rise more slowly in the second trimester. However, in some cases, low or decreasing levels of HCG indicate an impending miscarriage or other type of problem with the pregnancy. Surprisingly, there are even some cases where a woman's HCG levels are lower than expected and the pregnancy dates are correct,