Cervical Ectopic Pregnancy


Cervical Ectopic Pregnancy, Placenta (arrows)
Cervical Ectopic Pregnancy Trophoblastic Flow (arrows)
Twins with one non-viable aborting twin in the cervix (arrow)

Findings:

A cervical ectopic pregnancy is identified extending into the lower and mid-uterine segments. The placenta is identified in the cervical area and lower uterine segment (arrows). Trophoblastic flow (arrows) characterized by a high diastolic component (arrows) is clearly seen. This in addition to embryonic cardiac activity differentiates this from a spontaneous inevitable abortion.The second case is that of a twin gestation with one twin in the body of the uterus (arrowhead) and the other, a non-viable aborting twin in the cervix (arrow).

Discussion:

Cervical pregnancy is a rare form of ectopic pregnancy reported to occur between one in 1,000 and 1 in 50,000 pregnancies and in 0.15% of all ectopic pregnancies. It occurs when the fertilized ovum implants in the cervical mucosa distal to the internal cervical os. Several predisposing factors reported are: multiparity, prior abortion or instrumentation of the cervix or endometrial cavity. Most patients terminate spontaneously in the first trimester due to the unfavorable site of implantation. Patients often present with painless vaginal bleeding. If ultrasound is not fortuitously done the correct diagnosis may not be made until the time of a procedure. Patients may bleed profusely from the site of uterine implantation. This may occur even after removal of the products of conception because cervical tissue is predominantly fibrous connective tissue with only 15% of the cervix being smooth muscle. Relatively conservative measures such as KCl injection into the cervical pregnancy, maternal systemic methotrexate therapy and iliac vessel ligation have all been shown to be relatively sucessful at preventing life-threatening hemorrhage. However, the use of hysterectomy still remains high.

The first ultrasound description of a cervical pregnancy was in 1978. The abnormally low postion of the gestational sac is relatively easy to recognize sonographically. The difficult task is differentiating cervical pregnancy from a cervical stage of a spontaneous abortion. Several features of a cervical pregnancy will help make this distinction possible. In a cervical pregnancy, the uterine cavity above the cervix is often relatively small and the enlarged empty uterus may have an hourglass configuration with the lower uterine segment. In addition, the sac of a cervical pregnancy will be smooth and round or oval, with a yolk-sac or embryo inside. One can often identify the trophoblastic (placental) tissue with its characteristic doppler spectral pattern or of a high end-diastolic flow.

References:

Yankowitz J, Leake J, Huggins G, Gazaway P, Gates E. Cervical ectopic pregnancy: review of the literature and report of a case treated by single-dose methotrexate therapy. Obstet Gynecol Survey 45:405-414, 1990

Rosenberg RD, Williamson MR. Cervical ectopic pregnancy: avoiding pitfalls in the ultrasonographic diagnosis. J Ultrasound Med 11:365-367, 1992

Frates MC, Benson CB, Doubilet PM, DiSalvo DN, Brown DL, Laing FC et al. Cervical ectopic pregnancy:results of conservative treatement. Radiology 191:773-775, 1994

Zarabi M, Butkiewicz BL, Mazer J. Diagnosis of cervical pregnancy by ultrasonography. J Ultrasound Med 2:333-335, 1983

Sheldon RS, Aaro LA, Welch JS. Conservative management of cervical pregnancy. Am J Obstet Gynecol 87:504, 1963

Werber J, Prasadarao PR, Harris VJ. Cervical pregnancy diagnosed by ultrasound. Radiology 149:279-280, 1983

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