Ectopic Pregnancy Part 3

The group that we are interested in in terms of ultrasound imaging are women who are suspected of harboring an ectopic pregnancy and who have a positive pregnancy test. That constitutes the entire group of women in whom we are interested.

Within a group of women like that, depending on the socioeconomic strata that they are selected from, the ectopic pregnancy rate is going to range from 10% to 20%. So think of it as around 15%.

All women who are pregnant in the United States have about a 1 1/2% chance of having an ectopic pregnancy if they get pregnant which means that clinical symptomatology and physical findings increase your risk about 10 fold from 1 1/2% to 15%.

In this group of women, sonography is the pivotal examination because as we’ve already said, if you detect an intrauterine pregnancy in that group, you have effectively excluded ectopic pregnancy.

You haven’t absolutely excluded it because of the entity heterotopic pregnancy, but you have effectively excluded it.

So, in that group of women, if we look and find this gestation sac surrounded by myometrium and 360° and we identify that yolk sac, we know that this patient has essentially no significant risk for ectopic pregnancy, so essentially 0.

Now, importantly the flip side of that is, if you do not detect an intrauterine pregnancy and indeed you detect most intrauterine pregnancies with modern endovaginal sonography, the patient’s risk jumps to 55%.

So if the patient is an at risk patient and there is no visible intrauterine pregnancy, this patient has better than a 50/50 chance of having an ectopic pregnancy.

So, we have this woman who has no visible intrauterine pregnancy, and she has a positive pregnancy test and a clinical suspicion of ectopic pregnancy, she has better than a 50/50 chance of having an ectopic pregnancy.

What is that most women have if indeed only 15% of those that are suspected have an ectopic pregnancy? Well, obviously most of them have intrauterine pregnancies, and among those most are normal.

But a significant number are abnormal. We will discuss this topic in later articles. In Part IV, we will discuss further considerations in obstetric ultrasound for suspected ectopic pregnancies.

Author: Roy A. Filly, MD
Excerpted from:
Diagnostic Imaging Review: For Residents, Fellows and Radiologists
Female Pelvis Section