First-Trimester Diagnosis of Cesarean Scar Ectopic Pregnancy

Once considered extremely rare, implantation of a pregnancy within the scar of a previous cesarean section is becoming more common. In fact, its incidence is now higher than that of cervical ectopic pregnancies. We identified 5 cases of ectopic pregnancy implanted in a prior cesarean section scar at our institution since 2004. We outline the criteria for the first-trimester sonographic diagnosis of cesarean scar ectopic pregnancy, including a new sign of lower uterine segment ballooning, which has previously not been reported. Clinicians must have a heightened awareness of this serious and potentially fatal pregnancy complication. (C) 2008 Wiley Periodicals, Inc. J Clin Ultrasound 36:504-511, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jcu.20471