Human Chorionic Gonadotropin, or HCG, is a hormone produced during pregnancy and is often referred to simply as the “pregnancy hormone.” Its presence is what at-home and medical pregnancy tests detect to confirm conception. When a pregnancy loss occurs, monitoring the quantitative HCG level in the blood becomes a primary focus for medical providers to understand the status of the pregnancy and ensure the patient’s physical recovery. The decline of this hormone is a direct reflection of the body recognizing the end of the pregnancy. Tracking these HCG numbers serves as a laboratory marker for the body’s return to a non-pregnant state.
The Function of HCG in Healthy Early Pregnancy
The biological purpose of HCG is to establish and maintain the initial stages of a healthy pregnancy. This hormone is first secreted by the trophoblast cells, which eventually form the placenta, shortly after a fertilized egg implants in the uterine wall. Its job is to signal the corpus luteum to continue producing progesterone, which supports the uterine lining. In a viable pregnancy, HCG levels are expected to rise rapidly during the first trimester, typically doubling approximately every 48 to 72 hours. Medical providers often use this doubling rate, along with ultrasound findings, to assess the health and progression of the gestation.
Interpreting HCG Patterns During Pregnancy Loss
When a pregnancy is non-viable, the normal pattern of HCG doubling ceases. Instead of the expected rapid rise, the HCG levels may show a plateau, where the numbers remain relatively unchanged over several days of testing. Another common pattern is a slow or sluggish rise, where the level increases but falls significantly short of the required doubling rate. This delayed or insufficient increase signals that the trophoblast tissue is not developing properly. The definitive indicator of a miscarriage is a measurable and consistent drop in HCG concentration over multiple blood draws.
Medical Monitoring and Achieving HCG Resolution
Following a miscarriage, medical monitoring focuses on achieving HCG resolution. This process involves serial quantitative HCG blood draws (beta HCG tests) to track the hormone’s decline. The goal is to confirm the level has returned to the non-pregnant baseline, typically defined as below 5 milli-international units per milliliter (mIU/mL). Reaching this threshold indicates that all the pregnancy-related tissue has been cleared from the body. The rate at which HCG falls varies widely depending on how high the levels were at the time of the loss. If HCG levels were high, it can take four to six weeks or longer for the level to reach zero.
Addressing Persistent or Rising HCG Levels
While a declining HCG level is the expected outcome after a miscarriage, a failure to drop requires medical attention. If the HCG level plateaus or falls slower than expected, it may suggest retained products of conception (RPOC). This means placental tissue remains in the uterus, continuing to produce the hormone, and may require a medical procedure. A slow rise or a level that fails to drop significantly can also indicate an ectopic pregnancy, where the gestation implanted outside the uterus. A rare complication is gestational trophoblastic disease, such as a molar pregnancy, where abnormal tissue growth causes HCG levels to remain extremely high or rise rapidly.