A miscarriage is a challenging experience, both physically and emotionally. Many individuals navigate physical changes after a miscarriage, including understanding why a pregnancy test might still show a positive result. This article explains why pregnancy tests can remain positive after a miscarriage and the typical timeline for them to become negative.
Understanding hCG and Pregnancy Tests
Human chorionic gonadotropin (hCG) is a hormone produced by cells that form the placenta, nourishing a developing embryo after implantation. hCG signals the body to stop menstruation and supports other hormones, like progesterone and estrogen, necessary for maintaining the uterine lining during pregnancy. In pregnancy, hCG levels rise rapidly, often doubling every 72 hours, and usually peak between 8 and 11 weeks.
Home pregnancy tests detect hCG in urine using antibodies. A positive result indicates hCG levels above a threshold, generally 25 milli-international units per milliliter (mIU/mL). After a miscarriage, the body no longer produces hCG at the same rate, and levels decline. This decline is not instantaneous, so residual hCG can still be detected for some time.
Factors Affecting hCG Decline
The rate of hCG decrease after a miscarriage varies significantly, influenced by several factors. One factor is gestational age at the time of miscarriage. Later miscarriages mean higher initial hCG, requiring longer for the hormone to clear. Conversely, early losses, where hCG levels haven’t risen substantially, often result in a quicker return to baseline.
The completeness of the miscarriage also affects hCG decline. If all pregnancy tissue has been expelled, hCG levels generally drop more efficiently. However, if retained products of conception remain, they can continue to produce hCG, keeping levels elevated or declining slowly. The body’s metabolic rate also affects how quickly hormones are processed and cleared. Age can also influence this, with women over 35 sometimes experiencing a slower decline.
Typical Timeline for a Negative Test
A home pregnancy test is expected to show a negative result within a few days to several weeks following a miscarriage. While no universal timeline exists, hCG levels typically decrease by about 50% every 48 hours in the initial days. For most women, hCG levels generally return to a non-pregnant range (less than 5 mIU/mL) within 4 to 6 weeks after a complete miscarriage. However, later miscarriages can take longer, potentially up to two months or more, for hCG to become undetectable.
Home urine tests detect a certain hCG threshold, and may remain positive even with declining but detectable levels. To track decline more precisely, a healthcare provider might use a quantitative blood (beta-hCG) test. This test measures the exact amount of hCG in the blood, offering a more sensitive and accurate picture of decreasing levels compared to home urine tests.
When to Consult a Healthcare Provider
Consult a healthcare provider if a pregnancy test remains positive for an unexpectedly long time after a miscarriage, such as several weeks past the typical timeframe or three weeks after it began. Persistent positive results could indicate retained pregnancy tissue, or in rare cases, an ectopic or molar pregnancy, requiring medical evaluation.
Seek medical attention if new or worsening symptoms develop. These include signs of infection: fever above 38 degrees Celsius, chills, or green, yellow, or foul-smelling vaginal discharge. Heavy bleeding (soaking through more than two sanitary pads in an hour for over two hours) or severe abdominal pain and cramping warrant immediate medical consultation. A healthcare provider can offer guidance on physical recovery, emotional support, and future pregnancy planning.