Vital Signs: HR and BP

Traditionally in medical school we were taught that physiologic changes in pregnancy caused a drop in BP and an increase in HR but generally it was not well-defined if a new range of criteria was required to be considered normal. Emerging data shows that modest changes can be expected with pregnancy (i.e. slight increase in HR, possible small decreases in BP at 10 weeks gestation) but that in general these values should still be within the ranges of normal. With that, relative slight hypotension (i.e. systolics of 90’s) may be normal for your patient if they are a relatively young/healthy person without signs of compromise in end-organ perfusion; however each patient should be considered on an individual basis in this scenario. (Ref:

Hemodynamic Instability

If your pregnant patient is hemodynamically unstable, it is key to remember your primary patient is always the pregnant individual. Fetal viability/resuscitation is a secondary end-goal (though understandably a very important one if both can be achieved). We’ll go over some common conditions which can cause your patient to become unstable but will leave trauma and (pre)eclampsia (and HELLP as a complication) for another pearl another day.


  • Antibiotics: Check teratogenicity. This doesn’t take too long, can still get you in the 1-hour surviving sepsis mark, and will generally make mom and fetus happier if you choose ones less likely to cause malformations. Some common class B abx (little evidence of fetal risk) include cephalosporins, clindamycin, macrolides, flagyl, nitrofurantoin, penicillins, vancomycin. You can always check potential teratogenic effects beforehand and have a risk/benefit discussion with mom. However, if mom has anaphylaxis/severe drug reactions to certain agents then prioritizing mom’s safety should be made.
  • Vasopressors: all can potentially increase uterine vascular resistance = decrease in placental blood flow. However, don’t forget your primary patient and if mom is hypotensive refractory to fluid resuscitation then it may be imperative to start pressors. As Dr. DeVivo’s conference lecture emphasized, starting pressors should not be delayed. In the case of sepsis, levophed is still the first-line choice (Grade 1C: Phenylephrine is a good consideration for 2nd line agent as it has been well-studied in pregnant individuals.
  • Surgery: If surgical management is indicated to contain infection (i.e. appendicitis, esp if perforated or with abscess formation), pregnancy is not a contra-indication to surgical management. Get your consultants on board early. (Side note: pregnant individuals are more likely to progress to perforated appy given delays in obtaining appropriate imaging).

Vaginal Bleeding:

Vaginal bleeding beyond the first trimester is never benign (and many times in the first trimester is not benign either). Prognostically one third of fetuses will be lost if mom develops bleeding in the second trimester when the fetus is largely still nonviable. Of concern in this post is the 2nd trimester and beyond pregnant person with vaginal bleeding and hemodynamic instability. There are largely two diagnoses to consider in this scenario:

  1. Placenta previa: *painless bright red vaginal bleeding* are the key words you’ll encounter in board questions. Results from implantation of the placenta over the cervical os. Ideally should try to obtain an ultrasound to make the diagnosis before digital or instrumental probing as these can precipitate severe hemorrhage. Generally should leave speculum examination to OB however if you need to examine for whatever reason (OB not in your future hospital or critical to evaluate a crashing patient) then atraumatic insertion of the speculum only partially to evaluate if blood is coming from the cervix is preferred.
  2. Placental abruption: Separation of the placenta from the uterine wall. This condition is not always accompanied by vaginal bleeding depending on where the uterus implanted (i.e. if in the fundus could contain the bleeding). Approx 70% of cases will have vaginal bleeding. Generally it is painful with uterine tenderness, which can differentiate it from placenta previa. Is associated with trauma, but in the nontraumatic setting is associated with maternal hypertension and preeclampsia, maternal age (below 20 and above 35), parity of 3 or more, hx of smoking, thrombophilia, and cocaine use. There is wide variation in presenting symptoms and not all patients with this will be clinically unstable. On the other end, this condition can trigger further instability by setting off DIC.

Essentially with both of these diagnoses you will want OB input early with consideration of tocometry based on fetal age (often after 24 weeks when the fetus is considered viable but can be hospital/OB team dependent). Likewise, you will need to support their hemodynamics with consideration of fluid resus, transfusion (Rh negative blood if MTP), and pressors.

Endocrine emergencies:

  • Can be a whole pearl in and of itself but remember to keep a higher index of suspicion as many endocrine emergencies (hyperthyroidism/thyroid storm, DKA, Addisonian crisis, etc.) can be precipitated in the peri- and post-partum period.

Peripartum Cardiomyopathy/Arrhythmias:

  • Classically develops somewhere from the end of pregnancy to the post-partum period. Can be complicated by arrhythmias, cardiogenic shock, thromboembolic events. In general, if critically unstable then treat your pregnant patients as any other patients. This means as in the case of unstable tachycardias, electrical cardioversion and ACLS is indicated. LIkewise, if indicated, use pressors in cardiogenic shock.

Amniotic Fluid Embolus:

  • A rapidly fatal, anaphylactoid-type maternal response, consider this in your patients with quick clinical decompensation by rapid hypotension, hypoxia, and coagulopathy. Results when amniotic fluid is released into maternal circulation during intense uterine contractions or uterine manipulation. High mortality rate associated with this and several complications are common such as DIC, ARDS, LV dysfunction, and seizures (approx 20% of patients). Treatment recommendations are not well-validated given this is relatively uncommon but largely supportive care recommended with intubation prn, fluid resus, inotropic cardiac support, and anticipated management of a consumptive coagulopathy.

Last but not least which is obvious but always needs to be said: your unstable pregnant patient is of course still a regular human who can have regular human things that go wrong and make them unstable so don’t forget these on your differential!

Further Reading:

  • Links above
  • ACOG Practice Bulletin No. 211: Critical Care in Pregnancy (available through Sinai library)
  • Rosen’s Part V, Section 2 – Special Populations: The Pregnant Patient
May 2024