Human Chorionic Gonadotropin (HCG) is a hormone the placenta produces during pregnancy. This hormone plays a role in supporting the early stages of pregnancy by signaling the body to stop menstruation and stimulating the production of other hormones like progesterone and estrogen. Progesterone helps thicken the uterine lining and keeps the uterus relaxed, while estrogen assists with fetal organ development and increases blood flow to the placenta.
HCG Levels in a Healthy Pregnancy
HCG levels can be measured through urine or blood tests; blood tests provide quantitative results. In a healthy, early pregnancy, HCG levels typically rise rapidly, often doubling approximately every 48 to 72 hours. This doubling time is an important indicator of pregnancy progression. After 6 weeks, the doubling time can slow to 96 hours.
The concentration of HCG is measured in milli-international units per milliliter (mIU/mL). Non-pregnant women generally have HCG levels below 5 mIU/mL. Normal HCG levels vary widely by gestational age. For instance, at 3 weeks from the last menstrual period, levels might be 5–50 mIU/mL, increasing to 1,080–56,500 mIU/mL by 6 weeks.
HCG Levels Indicating Miscarriage Risk
Specific patterns of HCG levels can suggest a higher risk of miscarriage, though a single reading is rarely conclusive. A slow or absent rise in HCG, plateauing levels, or declining levels can indicate a nonviable pregnancy. For example, a slow rise occurs if HCG levels do not increase sufficiently over 48 hours in early pregnancy. Even a modest increase can sometimes be consistent with a viable pregnancy in very early stages.
Significantly low HCG levels for a given gestational age can indicate an issue. For instance, if HCG levels are below 1,200 mIU/ml but do not double within 48-72 hours, it raises concern. A decrease in levels, such as a drop from 120 mIU/mL to 80 mIU/mL over two days, can indicate the embryo is no longer developing. HCG levels can vary widely, so the trend observed over serial measurements is more informative than any isolated value.
Other Factors in Miscarriage Diagnosis
HCG levels are only one component in diagnosing a miscarriage. Transvaginal ultrasound is a primary tool for confirming pregnancy viability. An ultrasound can visualize structures like a gestational sac, yolk sac, fetal pole, and detect a fetal heartbeat at appropriate gestational ages. For instance, a gestational sac should be seen when HCG levels reach 1,000–2,000 mIU/mL, and an embryo with a heartbeat is visible when HCG levels are above 10,800 mIU/mL.
Miscarriage can also be diagnosed if a transvaginal ultrasound shows a crown-rump length (CRL) of 7 mm or more without a heartbeat, or a mean sac diameter (MSD) of 25 mm or more with no embryo. Common clinical symptoms associated with miscarriage include vaginal bleeding, which can range from light spotting to heavy flow, and abdominal cramping that may be more severe than menstrual pain. A sudden loss of pregnancy symptoms, such as nausea or breast tenderness, can also be a sign. A comprehensive diagnosis requires evaluating all these factors together, as bleeding and cramping can also occur in healthy pregnancies.
When to Consult a Healthcare Provider
It is important to seek medical attention if you experience concerning symptoms during pregnancy. These symptoms include heavy vaginal bleeding, severe abdominal cramping, or the passage of tissue or clots. Even light spotting or mild discomfort warrants a discussion with a healthcare provider to assess the situation.
If you have had HCG levels monitored and are concerned about the trend of your results, it is advisable to consult your doctor. Self-diagnosis based solely on HCG numbers is not recommended due to the wide range of normal variations and the need for a comprehensive medical evaluation. Your healthcare provider can determine the appropriate next steps, which may include additional blood tests or an ultrasound to clarify the pregnancy’s status.