Interstitial Pregnancy

Definition - What does Interstitial Pregnancy mean?

Interstitial pregnancy occurs when implantation of the embryo occurs in the uterus but is still an ectopic pregnancy as it is embedded outside the normal location of the inner lining of the uterus. A pregnancy that implants outside of the uterine lining (ectopic) is considered non-viable and cannot be carried to term.

In the case of interstitial pregnancy, implantation occurs in the part of the fallopian tube that pierces the uterus to empty into the uterine space. It is a rare condition representing only 2-4% of all tubal ectopic pregnancies and poses a high risk of complications. Just like any other kind of ectopic pregnancy, interstitial pregnancy can also impact future fertility.

Interstitial pregnancy is also known as cornual pregnancy.

FertilitySmarts explains Interstitial Pregnancy

The conditions that can increase the risk of interstitial pregnancy are as for other types of ectopic pregnancy include:

  • uterine abnormalities
  • previous ectopic pregnancy
  • surgical removal of the other fallopian tube
  • pelvic inflammatory disease
  • IVF and ovulation induction

In a woman presenting with signs and symptoms of ectopic pregnancy, the doctor will perform an ultrasound scan through the vagina. While detection of interstitial pregnancy has historically been challenging, the 3D scans yield a better view of the cornual regions of the uterus. Seeing a gestational sac located at one side outside the endometrium (inner lining) of the uterus is a hallmark feature of interstitial pregnancy.

Early detection of interstitial pregnancy with transvaginal ultrasound allows for early conservative treatment with medications. However, a later diagnosis in pregnancy warrants surgical removal of the affected part of the uterus and fallopian tube, or even, surgical removal of the entire uterus.


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