Synonyms: An interstitial pregnancy develops in the uterine portion of the falopian tube, a cornual pregnancy develops in the cornu of the uterus, angular pregnancy originates in the interstitial portion of the fallopian tube and grows into the adjacent uterine cavity.
Definition: Pregnancy located in the interstitial portion of the fallopian tube.
Prevalence: 1.4% of all pregnancies are ectopic; 2-4% of ectopic pregnancies are interstitial.
Etiology: Abnormal implantation of a fertilized ovum, in the interstitial portion of the fallopian tube.
Pathogenesis: Related to abnormal transport of the fertilized ovum within the fallopian tube. This can occur secondary to damage to the fallopian tube following pelvic inflammatory disease or prior conservative surgery for ectopic pregnancy. Hormonal imbalances caused by ovulation induction or exogenous estrogen and progesterone administration can also alter transport mechanisms within the fallopian tube. Cornual pregnancy is associated with bicornuate uterus.
Differential diagnosis: Abdominal pregnancy, other forms of tubal ectopic pregnancy.
Prognosis: The prognosis for the fetus is poor. The maternal mortality rate is 1 per 1000 interstitial pregnancies. This is twice the mortality rate of tubal ectopic pregnancies.
Recurrence risk: Among women who have had an ectopic, the subsequent overall conception rate is approximately 60%. Of these, 10% are repeat ectopic gestations.
Management: Surgical removal of the pregnancy via salpingectomy or salpingostomy. Medical management with methotrexate is used in abdominal pregnancies, but is not employed in ectopic gestations confined to the fallopian tube or uterus.
MESH Pregnancy, -tubal, -ectopic ICD9 633.4 CDC 633.400
Address correspondence to: Robert S. Shapiro, MD, Mount Sinai School of Medicine, Dept. of Radiology, Box 1234, One Gustave L. Levy Place, New York, NY 10029-6574. Ph: 212-241-7401; Fax: 212-427-8137
Interstitial pregnancy is an uncommon form of ectopic pregnancy with a disproportionately high incidence of complications. To the best of our knowledge, the case presented in this report is the first description of color Doppler sonography of this entity.
A 22-year-old G2P1 woman presented to her physician for an elective termination of pregnancy. The patient was 12 weeks pregnant by dates and had no prior history of ectopic pregnancy or pelvic inflammatory disease. An ultrasound performed at an outside institution was interpreted as abnormal. A gestational sac was identified outside the normal location in the uterus, but the exact location of the gestation was unclear. The patient was referred to our institution for further diagnostic evaluation and treatment.
An ultrasound exam performed at our institution revealed a gestational sac directly abutting the right side of the uterus..
Color Doppler sonography revealed blood flow associated with the sac, and a spectral tracing revealed a high velocity - low resistance pattern consistent with trophoblastic flow. The crown-rump length was 52 mm, consistent with a gestational age of 12 weeks. Because the gestational sac directly abutted the lateral aspect of the uterus and the pregnancy had progressed to a relatively advanced stage, it was felt that the ectopic gestation was most likely interstitial in location. Because of the advanced stage of the gestation, and since an abdominal pregnancy could not be excluded with certainty, a preoperative angiogram and embolization procedure were performed. The angiogram revealed a vascular extrauterine mass consistent with an ectopic gestation (fig. 1). The embolization procedure was performed to minimize blood loss during the ensuing surgery.