There are many challenges in caring for patients with PAH. We ask our patients to take many different medications to help treat their disease process and we ask them to put up with side effects from these medications. We ask our patients to change their lifestyles and eating habits. One of the greatest challenges is the issue of pregnancy. PAH is particularly common in young women who might otherwise consider either starting a family or adding to their family.
Why is Pregnancy Harmful to a Woman with Pulmonary Arterial Hypertension?
Understanding the normal changes to a woman’s body that take place during pregnancy helps us understand why carrying a pregnancy can be so dangerous. A woman’s body gradually retains salt and water during pregnancy such that by the end of the third trimester their blood volume has increased by 50%. There is an increase in 6 to 8 liters of water and about 1000meq of sodium. So if a woman had a total blood volume prior to pregnancy of 5 liters then at 36 weeks their blood volume would be 7.5 liters. Heart rate increases by 15 to 20 beats per minute and cardiac output increases up to 50%. This dramatic increase in blood volume is accompanied by a mild anemia. The anemia is well tolerated but in PAH the right ventricle is asked to work much harder. In a woman without pulmonary hypertension the heart has no problem meeting the increased work load that is required but in PAH the added fluid can result in progressive right heart failure and death.
In addition to the extra work that is required of the right ventricle in pregnancy, several of the medications that are commonly used to treat pulmonary arterial hypertension are teratogenic (very harmful to the growing fetus). Additional hurdles include the stress of delivery. Normal labor requires a woman to push very vigorously to help the baby exit the birth canal. This type of pushing can cause fainting and dangerously low blood pressure in a patient with PAH. Many women choose to have a “spinal”. This is an injection of medication to reduce the amount of pain and pressure experienced during the peak of labor. In patients with pulmonary hypertension, this spinal injection can precipitate life-threateningly low blood pressure. Cesarean section is sometimes required to safely deliver the baby. Options for making this comfortable include spinal injection of anesthesia or general anesthesia (being put to sleep). The latter can be very dangerous for PH patients even when performed by anesthesiologists expert in PAH management
Check back soon for Part 2 of pregnancy and pulmonary hypertension.