Approach to third trimester bleeding: Clinical sciences

Third trimester bleeding is defined as bleeding from 28 weeks of gestation through delivery, and is considered an obstetric emergency if severe or accompanied by maternal or fetal instability. Bleeding at this stage of pregnancy can be classified based on the presence or absence of abdominal pain. Painless causes include cervical or vaginal lesions, placenta previa, and ruptured vasa previa; while painful causes include placental abruption, uterine rupture, or normal labor. Severe third trimester bleeding requires rapid assessment and stabilization, along with timely management in order to prevent maternal and fetal morbidity and mortality.

Your first step in evaluating a patient presenting with third trimester bleeding is to perform a CABCDE assessment along with a primary obstetric survey to determine if they are stable or unstable. If the patient is unstable, control any life-threatening hemorrhage. Then stabilize the airway, breathing, and circulation. Obtain IV access if not already present, and monitor maternal vital signs closely. Once the patient is stabilized, be certain to assess the fetal status by monitoring the fetal heart rate. A labor evaluation may then be performed by testing for rupture of membranes and checking cervical dilation.

Here’s a clinical pearl! A digital cervical exam should never be performed prior to confirming placental location, either through a review of the patient’s prenatal records or on a bedside ultrasound if not previously documented. Palpation of a placenta previa through a partially dilated cervix can result in life-threatening hemorrhage and should be avoided.

Alright, now let’s talk about stable patients. First, obtain a focused history and physical examination. During history, characterize the bleeding and take notes of the quantity, the presence or absence of abdominal pain, and any associated precipitating events. Specifically, question the patient regarding any recent history of trauma, and if reported, whether direct abdominal contact occurred. Also assess if the patient has any prior uterine surgery that disrupted the myometrial layer of the uterus, such as a c-section or myomectomy. Lastly, the presence or absence of abdominal pain will help narrow down your differentials, so be sure to assess for abdominal pain.

First, let’s talk about patients who present with third trimester bleeding in the absence of any abdominal pain or contractions. In these patients, the primary diagnoses to consider are a cervical or vaginal lesion, placenta previa, or ruptured vasa previa.

Once you have classified the bleeding as painless, your next step is to perform an obstetric ultrasound to assess the placenta for any abnormality. Additionally, perform a speculum exam to evaluate for active bleeding versus old blood and to assess the amount of bleeding present.

Let’s start with cervical or vaginal lesions. Patients will report a history of light vaginal bleeding, sometimes occurring after recent intercourse. In these patients, your physical examination will play a key role in confirming your diagnosis. On visual inspection of the cervix and vagina, you will see a lesion responsible for the painless bleeding, such as a friable cervix, cervical polyp, or other abnormality. Ultrasound will show a normal placenta, supporting the diagnosis of a cervical or vaginal lesion.

Here’s a clinical pearl! Cervical friability refers to cervical tissue that’s easily irritated, making it more prone to inflammation, bleeding, or tearing. This can be normal in pregnancy, but may also be related to cervicitis from infection, most commonly chlamydia, gonorrhea, or bacterial vaginosis.

Let’s move on to placenta previa, which occurs when the placenta partially or completely covers the internal cervical os. It’s most commonly detected on routine anatomy ultrasound around 18 to 20 weeks of gestation. If the patient reports abrupt onset vaginal bleeding in the context of a known placenta previa or history of a previa, your diagnosis is most likely bleeding from the placenta previa. History might be significant for a previous cesarean delivery, which is one of the strongest risk factors. This finding may assist in diagnosis in cases where placental location is unknown.

On physical exam, you may observe either substantial or light bleeding. Typically, the uterus will not be tender nor have increased tone. The fetal heart rate tracing may show a nonreassuring pattern depending on the quantity of bleeding and maternal vital signs.

Finally, the ultrasound will show homogeneous placental tissue extending over the internal cervical os. If this is present, you have your diagnosis of placenta previa.

Okay, let’s go ahead and discuss the last cause of painless bleeding called ruptured vasa previa. This one is the least common cause, but requires the most rapid action to prevent fetal compromise. Vasa previa occurs when unprotected umbilical vessels run through the amniotic membranes and pass over the cervix. If a patient reports an abrupt onset of vaginal bleeding, which occurred at the time of membrane rupture, think about ruptured vasa previa as the cause.

Additionally, a patient may have a known vasa previa or abnormal placentation, such as a velamentous cord insertion, bilobed placenta, or a placenta with a succenturiate lobe.