Normal Pulmonary Artery Pressure in Pregnancy
In a pregnant woman with no underlying medical conditions, normal mean pulmonary artery pressure (mPAP) remains 14-20 mmHg at rest, identical to non-pregnant individuals. 1
Defining Normal vs. Abnormal Pressures
The threshold for pulmonary hypertension does not change during pregnancy:
- Normal mPAP: 14-20 mmHg at rest 1
- Uncertain significance: 21-24 mmHg - warrants close follow-up but clinical significance remains unclear 1
- Pulmonary hypertension: ≥25 mmHg (older definition) or >20 mmHg (newer definition per recent guidelines) 1, 2
Critical Clinical Context for Pregnancy
While normal PA pressures don't change in pregnancy, the clinical implications of even mildly elevated pressures are dramatically different:
- Pregnancy with pulmonary hypertension carries 17-33% maternal mortality in recent studies (historically 30-50%) 1, 3
- Even moderate pulmonary hypertension can worsen during pregnancy due to decreased systemic vascular resistance and right ventricular volume overload 1, 3
- No safe cut-off value exists - even pressures in the 30 mmHg range (e.g., post-ASD closure) carry uncertain but potentially significant risk 1
Physiologic Changes to Consider
Pregnancy induces substantial hemodynamic changes that stress the pulmonary circulation, but these changes do not alter what constitutes "normal" PA pressure:
- The cardiovascular system undergoes increased blood volume, cardiac output, and decreased systemic vascular resistance 3
- These changes can unmask or worsen underlying pulmonary vascular disease even when baseline pressures appeared only mildly elevated 1, 3
- Maternal deaths typically occur in the last trimester or first months postpartum due to pulmonary hypertensive crises, thrombosis, or right heart failure 1, 3
Measurement Considerations
- Right heart catheterization remains the gold standard for measuring mPAP, with the same normal values (14-20 mmHg) applying to pregnant and non-pregnant patients 1, 2
- Echocardiography can estimate PA systolic pressure but is insufficient alone for treatment decisions regarding pulmonary hypertension therapy 2
Key Clinical Pitfall
The most important caveat is that pregnancy is contraindicated (WHO class IV) in women with established pulmonary hypertension regardless of severity, given the high maternal mortality risk 3, 4, 5. If pulmonary hypertension is discovered during pregnancy, immediate referral to a specialized multidisciplinary center is mandatory 3.