There is some connection between human chorionic gonadotropin, or HCG levels and ectopic pregnancy. One of the ways a doctor may detect an ectopic pregnancy is by analyzing the levels of HCG, a hormone produced during pregnancy, in a woman's blood. When blood tests are done and HCG levels seem 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 via an ultrasound; if 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 an early, normal, healthy pregnancy, HCG levels usually rise steadily; in most cases, they double every two to three days. To determine if a pregnancy is healthy and viable, doctors typically take blood tests to assess HCG levels. If HCG levels are not as high as expected for the stage of pregnancy, doctors may order repeat blood tests. These blood tests are then used to check whether or not a woman’s HCG levels are continuing to rise and double as expected. Since there is a connection between HCG levels and ectopic pregnancy, low or declining levels on these repeat HCG tests usually mean further evaluation is necessary.
Doctors do not usually rely on the connection between HCG levels and ectopic pregnancy alone when determining whether or not a woman has a pregnancy developing in a fallopian tube. Instead, doctors may perform an ultrasound once levels have reached 2,000 milli-international units per milliliter to check for a developing pregnancy in the uterus. Its absence sometimes, but not always, means an ectopic pregnancy. Pelvic exams and other tests may be performed to confirm a diagnosis.
Though there is a connection between HCG levels and ectopic pregnancy, low, slow-to-rise, and declining HCG levels do not always indicate an ectopic pregnancy. Sometimes low HCG levels may simply mean a pregnancy is not as far along as originally thought. Slow-to-rise levels may even indicate that a pregnancy is further along than expected, as HCG levels typically rise more slowly in the second trimester. In some cases, however, low or declining HCG levels indicate an impending miscarriage or another type of problem with the pregnancy. Surprisingly, there are even some cases in which a woman’s HCG levels are lower than expected and the pregnancy dates are correct, but there is absolutely nothing wrong with the pregnancy.