Molar pregnancies are associated with extremely high levels of BhCG, out of proportion to the stage of pregnancy. However, urine and serum BhCG assays can paradoxically be negative, despite the high BhCG levels, leading to misdiagnosis and delayed treatment. This is due to saturation of the assay by the BhCG molecules. We present such a case where the initial urine pregnancy test was negative in an advanced complete molar pregnancy. Primary care and emergency department physicians should be mindful of this possibility and go on to do serum BhCG with sample dilution in cases where pregnancy is strongly suspected. Molar pregnancy is an abnormal pregnancy event. There is abnormal proliferation of trophoblastic cells, with potential for malignancy and metastasis. The incidence appears to vary in different regions, with increased incidence in Asia. They present with exaggerated symptoms of pregnancy: severe nausea and vomiting, bleeding per vagina, abdominal pain or mass. They may also present with thyrotoxicosis or preeclampsia. These symptoms are thought to be due to grossly elevated levels of BhCG. BhCG is produced by trophoblastic tissue; the excessive proliferation of trophoblast in hydatidiform mole produces extremely high levels of BhCG. Very occasionally, a falsely low serum BhCG may occur in molar pregnancy. This phenomenon is known as the hook effect.  A 26 year old Vietnamese lady, gravida 4 para 2 (2 vaginal deliveries, 2 terminations) presented at 4 weeks and 2 days amenorrhoea to the primary health physician for main complaint of enlarging pelvi-abdominal mass. She also had pedal edema, fatigue and orthopnea of a few days’ duration. She had no significant past medical history and was well before the onset of her symptoms. She had a regular 30 day menstrual cycle; however the last menstrual period was different and consisted of spotting only. She had a normal sexual relationship with her husband and was not using any contraception. On examination, she was tachycardic at 128 beats per minute and had bibasal crepitations on auscultation of her lungs. Temperature, blood pressure and oxygen saturations were within normal limits. A non-tender mass was felt arising from the pelvis extending to the umbilicus. Cervix was posterior and not well visualized, possibly due to compression from the pelvic mass. Blood stains were seen in the vagina. Bilateral pitting edema was present up to the ankle. Urine pregnancy test was negative.

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With Regards,
Sara Giselle
Associate Managing Editor
Global  Journal of Digestive Diseases