Image 1: POCUS transabdominal sagital view of a first trimester pregnancy.
Image 2: An endomyometrial mantle measurement of 1.27 cm. The measurement is taken at the thinnest portion of the uterine wall from outer border of gestational sac to outer border of the uterus.
Image 3: An endomyometrial mantle measurement of 1.39 cm. The measurement is taken at the thinnest portion of the uterine wall from outer border of gestational sac to outer border of the uterus.
In order to diagnose an intrauterine pregnancy (IUP) on point of care ultrasound (POCUS) in the emergency department, you need to see at minimum 3 things.
1) Both bladder and uterus.
2) Gestational sac with a yolk sac within.
3) An myometrial mantle measurement of at least 8 mm. This measurement is taken at the thinnest portion of the uterine wall. The real goal of this measurement is to safely ensure not a cornual / interstitial ectopic, which if not caught will lead to maternal hemorrhage.
Take home point: The myometrial mantle measurement is necessary to ensure the health of mom. If a gestation is growing too far in the periphery of the uterus, there is risk of uterine rupture and subsequent hemorrhage. We are encouraging you to take that measurement every time you are attempting to diagnose a first trimester IUP.
Thought experiment: A fetal heartbeat can be seen in every type of ectopic pregnancy, so if you’re depending on that aspect of a first trimester pregnancy evaluation to diagnose an IUP, please only do so after you’ve measured the myometrial mantle.