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

Sep 29, 2026

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A woman in her early 20s presented with abdominal pain and heavy bleeding, unaware she was 18 weeks pregnant. Despite repeatedly negative urine pregnancy tests, imaging identified intrauterine fetal demise with ultrasound findings consistent with approximately 18 weeks’ gestation and no cardiac activity. Serum β-hCG measured only 80 IU/L, highlighting that miscarriage and fetal demise can produce false-negative qualitative tests due to lower or declining hCG levels. The report emphasizes maintaining diagnostic suspicion and using early imaging in atypical presentations.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages3

Reading Time8 min

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Abstract

Introduction

Case Presentation

Discussion

Diagnostic challenges

Hormone testing limitations

Review began 11/30/2025 Review ended 12/04/2025 Published 12/05/2025 © Copyright 2025 Desouky. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 4.0. , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited. DOI: 10.7759/cureus.98517 Open Access Case Report Unrecognised Second-Trimester Pregnancy With Fetal Demise Presenting as Acute Abdomen and a Negative Pregnancy Test Marwa E. Desouky 1 1. Obstetrics and Gynaecology, Northampton General Hospital, Northampton, GBR Corresponding author: Marwa E. Desouky, [marwa.desouky@nhs.net](marwa.desouky@nhs.net) Abstract 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. Categories: Obstetrics/Gynecology Keywords: abdominal pain, fetal demise, intrauterine fetal demise, negative pregnancy test, unrecognised pregnancy, urine β-hcg Introduction Second-trimester fetal demise is typically associated with well-recognised clinical features such as cessation of fetal movements, abdominal distension, amenorrhoea, and persistently positive pregnancy tests. Pregnancy detection usually relies on the presence of β-human chorionic gonadotropin (β-hCG), which remains elevated throughout gestation. However, unrecognised or “cryptic” pregnancies pose a diagnostic challenge, particularly when patients continue to experience bleeding resembling menstruation or present with nonspecific symptoms, such as abdominal pain, leading clinicians to initially consider more common gynaecological conditions [1] . Although uncommon, false-negative urine or serum β-hCG tests have been reported in the literature, even in cases of advanced pregnancy or trophoblastic disease. One well-documented cause is the “hook effect,” in which extremely high β-hCG concentrations saturate the antibodies in the immunoassay, preventing proper complex formation and resulting in a falsely negative result [2,3] . Case reports describe patients with complete molar pregnancies who had repeatedly negative urine pregnancy tests, with diagnosis only confirmed after quantitative serum β-hCG testing with dilution [3] . Another case involved an adolescent presenting with abdominal pain and bleeding with a negative urine test; subsequent evaluation revealed a molar pregnancy following serum β-hCG measurement and imaging [3] . In this report, we describe a 24-year-old woman who presented with abdominal pain and what she believed to be a heavy menstrual period, later found to have a second-trimester fetal demise despite repeatedly negative urine β-hCG testing. This case emphasises the need to maintain a broad differential diagnosis in reproductive-aged women presenting with abdominal pain or abnormal bleeding, even when qualitative pregnancy tests are negative, and highlights the limitations of urine β-hCG assays in atypical presentations [1,2] . Case Presentation A woman in her early 20s, P2, presented to the emergency department with heavy per vaginal bleeding and lower abdominal pain. Her obstetric history included two previous lower-segment caesarean sections, with no other significant medical or surgical history. She reported regular menstrual cycles and stated that she was on day 6 of what she believed to be her current menstrual period. Initial investigations in the emergency departmen

FAQs

Why can urine pregnancy tests be negative in second-trimester fetal demise?

In miscarriage or fetal demise, human chorionic gonadotropin may be lower than expected or decline, so qualitative urine tests can be falsely negative despite advanced gestation.

What imaging findings confirmed the diagnosis in this case?

CT revealed fetal bones within the uterus, and bedside transabdominal ultrasound showed an intrauterine fetus without detectable cardiac activity, with femur length corresponding to about 18 weeks.

How was the patient managed after admission?

The patient remained haemodynamically stable and experienced a spontaneous complete miscarriage the next morning without needing surgical intervention.

Sep 29, 2026

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