Human Chorionic Gonadotropin (HCG) is a hormone produced by cells that form the placenta, which nourishes a developing embryo. It signals pregnancy and helps maintain early gestation. An ectopic pregnancy occurs when a fertilized egg implants outside the uterus, usually in a fallopian tube. Understanding HCG levels helps evaluate pregnancy health and location.
HCG in a Healthy Pregnancy
In a healthy, intrauterine pregnancy, HCG levels rise rapidly during the early weeks. After implantation, the placenta secretes HCG, and levels double approximately every 48 to 72 hours for the first 6 to 7 weeks. This doubling rate indicates expected progression.
HCG levels reach their peak between 8 and 11 weeks of gestation. After peaking, levels decline and stabilize for the remainder of the pregnancy. HCG’s primary function in early pregnancy is to support the corpus luteum, a temporary ovarian structure that produces progesterone. Progesterone enriches the uterine lining and sustains the fetus until the placenta takes over hormone production.
HCG in Ectopic Pregnancy
In ectopic pregnancy, HCG levels exhibit an atypical rise compared to a healthy pregnancy. While HCG levels increase, the rate of increase is slower than expected. For instance, the HCG level may increase less than 66% over a 48-hour period, a deviation from the typical doubling time in viable intrauterine pregnancies.
Beyond a slow rise, HCG levels in an ectopic pregnancy might plateau or even fall. These abnormal trends occur because the fertilized egg implants in a location that cannot support its growth. The compromised environment leads to inefficient hormone production by the improperly located tissue. Although detectable, its irregular behavior indicates the pregnancy may not be viable or is located outside the uterus.
How Ectopic Pregnancy is Diagnosed
Diagnosing an ectopic pregnancy relies on combined assessments, as HCG levels alone are not sufficient for a definitive diagnosis. Healthcare providers use serial HCG measurements, tracking hormone levels over several days to observe their trend. An HCG level that rises slowly, plateaus, or declines raises suspicion for an ectopic pregnancy.
Serial HCG testing is used with transvaginal ultrasound. This imaging provides a detailed view of reproductive organs, determining gestational sac location. If HCG levels are above a threshold (e.g., 1,000-2,000 mIU/mL) but no gestational sac is visible in the uterus via ultrasound, it suggests an ectopic pregnancy or a very early intrauterine pregnancy. Clinical symptoms like pelvic pain, vaginal bleeding, or dizziness also guide diagnosis and prompt further investigation.
Importance of Early Detection
Prompt, accurate diagnosis of an ectopic pregnancy is important due to potential serious complications. If not identified and treated early, the growing tissue can rupture the fallopian tube, the most common site. A ruptured ectopic pregnancy can cause severe internal bleeding, leading to hemorrhagic shock and posing a life-threatening risk.
Ectopic pregnancies rarely result in a viable birth, making early intervention necessary to safeguard health. Seeking immediate medical attention for symptoms like persistent abdominal pain, unusual vaginal bleeding, or signs of shock (dizziness or fainting) is important. Early detection allows for timely medical management, preventing severe complications and preserving future fertility.