Unrecognised Second-Trimester Pregnancy With Fetal Demise Presenting as Acute Abdomen and a Negative Pregnancy Test.

A woman in her early 20s presented with abdominal pain and a heavy period, unaware that she was 18 weeks pregnant. Despite a negative urine pregnancy test, imaging revealed intrauterine fetal demise. This rare case highlights the importance of maintaining clinical suspicion and performing early imaging, as pregnancy tests may yield false-negative results in cases of miscarriage and fetal demise. Human chorionic gonadotropin (hCG) is produced by the placenta, but when a pregnancy fails to develop normally, such as in miscarriage, hCG levels may be lower than expected or decline, leading to negative test results despite advanced gestation.