Asthma's effect on pregnancy

I am 11-weeks-pregnant. I have asthma and am working with my pulmonologist and OB/GYN to manage severe symptoms I am having with a cold. I am terrified of the trauma my asthma has taken on the baby, as well as the effect of the limited medications I have to take. What is your experience with pregnant asthmatics?

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ABOUT THE EXPERT

Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

Asthma and pregnancy bring up many issues such as the impact of the disease upon the health and well being of mother and baby, the necessity for increased surveillance of the condition and new adaptations to the management strategies proposed in its treatment.

Asthma is an inflammatory disease of the respiratory tract causing spasms in the bronchials which can affect patients in a variety of age groups, including women of childbearing age. A number of studies have shown that about one to four percent of all pregnancies are complicated by bronchial asthma. However, the true prevalence may be much higher because, in many cases, the condition goes undiagnosed.

Asthma may have its onset for the first time during pregnancy or may be worsened by pregnancy. Either way, undertreated or uncontrolled asthma can have serious effects on both the mother and fetus.

Maternal complications of uncontrolled asthma can include preeclampsia/eclampsia, vaginal hemorrhage and premature labor. Neonatal complications may include intrauterine growth retardation, preterm birth and increased risk of perinatal mortality.

If the mother has an acute asthma attack during pregnancy, airway inflammation or bronchoconstriction may causing respiratory distress. The woman's ventilation rate increases and can change the acidity of the blood. If the attack worsens, further airway narrowing causes impairment of air exchange.

As the asthma attack worsens, arterial oxygen can decline. If left unchecked, the airway narrowing and the gas exchange abnormalities can be fatal.

The main concern in the pregnant woman with asthma is adequate oxygen delivery to the mother and fetus. In asthma, this delivery of oxygen can be compromised. The fetus develops in an environment of low oxygen tension relative to the mother. This is due to the design of the placenta. The maternal uterine blood vessels and the fetal umbilical blood vessels run in parallel and oxygen is exchanged passively. Consequently, fetal oxygen pressure can never exceed maternal venous oxygen pressure.

But babies adapt to lower oxygen levels. In light of the low oxygen tension of blood delivered to the fetus, other mechanisms must be used to enhance fetal oxygenation. In this respect, fetal hemoglobin plays an important role. Fetal hemoglobin has a higher affinity for oxygen relative to adult hemoglobin. Further, fetal hemoglobin is more highly concentrated as compared to adult hemoglobin, which increases the oxygen carrying capacity of the fetal blood. An additional method enhancing fetal oxygenation is the increased blood flow to some fetal organs compared with adult organs. Blood flow to select fetal organs can be greater than twice that of the adult organs.

In regard to the safety of asthma medications, in a large study of 824 pregnant women with asthma, no significant association was found between use of most common asthma medications during pregnancy and adverse perinatal outcomes. Specifically, inhaled beclomethasone dipropionate, metaproterenol and albuterol were not found to be associated with congenital malformations. Oral corticosteroids were associated with a higher risk of preeclampsia (pregnancy induced hypertension).

When asthma is actively controlled, the baby's prognosis is similar to the general population. For example, one series reported on 80 pregnancies in 73 asthma patients who required inhaled or oral corticosteroids for moderate to severe asthma. Patients with at least one episode of status asthmaticus displayed an increased incidence of intrauterine growth retardation and lower birth weights. In the women in this series who experienced no episodes of status asthmaticus, however, results were similar to the nonasthmatic population. Collectively, these and other studies indicate the importance of controlling asthma in the pregnant patient.

Studies confirm what would be expected knowing that fetal oxygenation is related to maternaloxygenation: uncontrolled asthma can lead to morbidity in both the mother and fetus. If asthma is controlled, however, these adverse outcomes can generally be avoided and normal outcomes usually can be achieved.

It sounds like you are being cared for by a team of experts. In my experience, women with treated asthma have very normal pregnancies and very healthy babies.

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