PARIS — Pregnancy is a period of asthma instability; it entails an increased risk for exacerbations. While therapeutic de-escalation, if not the outright cessation of maintenance treatment, is common, experts used the 19th Francophone Congress of Allergology to emphasize the importance of well-controlled asthma for the mother, the fetus, and the pregnancy.
About 12% of women of childbearing age have asthma. It is the most common chronic condition in pregnant women. Pregnancy affects asthma, and vice versa. Due to mechanical, hormonal, and immunological changes, allergic conditions, including asthma, can worsen.
First, pregnancy exerts mechanical pressure on respiratory function because of the progressive increase in uterine volume, diaphragm elevation, and various anatomical changes leading to chest expansion. The latter changes include increased subcostal angle, anteroposterior and transverse diameters, and thoracic circumference.
Respiratory function is affected, with a decrease in functional residual capacity and expiratory reserve volume but an increase in inspiratory capacity, maximal ventilation, and tidal volume. The resulting hyperventilation manifests clinically as dyspnea, which affects up to 70% of pregnant women and can be mistaken for exacerbation symptoms.
Besides mechanical impact, hormonal changes occur during pregnancy, including elevated estrogen and progesterone levels. Placental hormones increase during the third trimester. These steroid hormones weaken the respiratory mucosa through structural changes in the bronchial wall and the activity of inflammatory cells involved in asthma, while influencing bronchial muscle tone. Estrogens have a dual effect. They are immunostimulatory at low doses and immunosuppressive at high doses (as in late pregnancy). This phenomenon suggests a role in immune tolerance toward the fetus.
The Rule of Thirds
Asthma progression during pregnancy is unpredictable. According to older studies, about one third of cases remain stable, one third worsen, and one third improve. In 60% of cases, the course remains similar from one pregnancy to another. Pregnancy is considered a period of asthma instability, with a doubled risk for exacerbation compared with nonpregnant women. Several pregnancy-specific factors contribute, including gastroesophageal reflux, excessive weight gain, active or passive smoking, and usual risk factors like infections. However, the main risk factor for exacerbation and loss of asthma control is insufficient maintenance treatment.
“The control of asthma during pregnancy is influenced by pregnancy itself, but especially by the severity of the disease before pregnancy and the underuse of inhaled corticosteroids,” said Mohammed Tawfik el Fassy Fihry, MD, pulmonologist at Ibn Sina Souissi Hospital in Rabat, Morocco. “This treatment insufficiency is the main cause of poor asthma control and sometimes of severe exacerbations.”
Inhaled Corticosteroid Often Insufficient
A 2017 study conducted in France found that one third of women had their asthma treatment reduced in the first trimester of pregnancy. Another observation was the frequent replacement of fixed combinations (such as long- and short-acting bronchodilators and inhaled corticosteroids) with simple inhaled corticosteroid therapy.
“A significant proportion of pregnant women on maintenance therapy decide to stop it as soon as they discover their pregnancy,” said Chantal Raherison-Semjen, PhD, coordinator of the Women and Lung group of the French Society of Pulmonology (SPLF) and of the pulmonology department at the University Hospital of Pointe-à-Pitre in Guadeloupe, France. “Treating physicians also often opt for therapeutic de-escalation, which involves stopping long-acting bronchodilators in favor of only inhaled corticosteroid therapy, which is usually insufficient for optimal asthma control.”
In severe exacerbations, especially during the first trimester of pregnancy, poorly controlled asthma can lead to complications in fetal development, such as low birth weight, intrauterine growth retardation, prematurity, and congenital malformations.
It can also affect maternal health by increasing the risk for gestational diabetes and affecting the course of pregnancy itself, favoring the occurrence of preeclampsia, placenta previa, placental abruption, premature rupture of membranes, spontaneous miscarriage, cesarean section, and hemorrhagic complications before and after delivery.
“When a pregnant woman presents to the emergency room due to an asthma exacerbation, physicians are often reluctant to administer optimal treatment for fear of the effects of bronchodilators and systemic corticosteroids,” said Dr. Raherison-Semjen. “As a result, these women generally receive less effective treatment in such situations, compared with nonpregnant women. This is despite the risk that severe asthma exacerbations pose to the mother and her child.”