Low lying gestation sac in early pregnancy-an algorithmic approach with ultrasound markers

Abstract

The differential diagnosis of low lying gestational sac in ultrasound at early pregnancy scan varies from benign entities like cervical stage of miscarriage to morbid conditions like caesarean scar pregnancy and cervical pregnancy. Abnormal placental invasive pregnancies also manifest as low lying gestational sac at cervico-isthmic junction. Early diagnosis using simple ultrasound criteria can prevent severe life-threatening complications. Various clues on ultrasonography can easily differentiate between a caesarean scar pregnancy, cervical pregnancy, cervical stage of miscarriage or a low implanted sac which may be a precursor for morbidly adherent placenta. In this article we have reviewed the ultrasound markers in a case of inevitable abortion, a case of cervical pregnancy, 3 cases of caesarean scar pregnancy and 2 cases of morbidly adherent placenta. Comparison of anterior myometrial thickness in a low implantation of sac and caesarean scar pregnancy has been demonstrated. Sometimes a small cervical polyp can mimic a low lying gestation sac and the differential diagnosis with ultrasound has been discussed. Three dimensional ultrasound examinations for spatial location of the sac provide additional information for further management and aids in precise diagnosis. Though other investigations like MRI may also be beneficial in arriving at a diagnosis, its routine usage may be limited due to the cost and availability. Hence defining ultrasound markers in a low lying gestational sac helps in early diagnosis which can prevent fertility losses incurred due to inadvertent management