Possible teratogenic or adverse fetal efects of drugs given to control asthma have been a concern. Several reports show a slightly greater risk for varied abnormalities such as cleft lip and palate and autism spectrum disorders. However, not all studies have veriied this (Eltonsy, 2016; Gidaya, 2016; Murphy, 2013b; Wang, 2014). It is worrisome that up to half of these women discontinue essential treatment between 5 and 13 weeks' gestation (Enriquez, 2006).
he subjective severity of asthma frequently does not correlate with objective measures of airway function or ventilation. Although clinical examination can also be an inaccurate predictor, useful signs include labored breathing, tachycardia, pulsus paradoxus, prolonged expiration, and use of accessory muscles. Signs of a potentially fatal attack include central cyanosis and altered consciousness.
Arterial blood gas analysis provides objective assessment of maternal oxygenation, ventilation, and acid-base status. With this information, the severity of an acute attack can be assessed (see Fig. 51-1). That said, in a prospective evaluation, Wendel and associates (1996) found that routine arterial blood gas analysis did not help to manage most pregnant women who required admission for asthma control. If used, the results must be interpreted in relation to normal values for pregnancy. For example, a Pco2>35 mm Hg with a pH <7.35 is consistent with hyperventilation and CO2 retention in a pregnant woman.
Pulmonary function testing should be routine in the management of chronic and acute asthma. Sequential measurement of the FEV1 or of the peak expiratoy low rate-PEFR-is the best measure of severity. n FEV1 less than 1 L, or less than 20 percent of predicted value, correlates with severe disease defined by hypoxia, poor response to therapy, and a high relapse rate. The PEFR correlates well with the FEVl, and it can be measured reliably with inexpensive portable meters. It is advantageous for each woman to determine her own baseline when asymptomatic to compare with values when symptomatic.
• Management of Chronic Asthma
Asthma management by an experienced team produces the most salutary outcomes (Bonham, 2017; Lim, 2014; Wendel, 1996). Management guidelines include: 1.
Patient education-general asthma management and its efect on pregnancy.
2.
Environmental precipitating factors-avoidance or control.
Viral infections that include the common cold are frequent triggering events (Ali, 2013; Murphy, 2013a).
3.
Objective assessment of pulmonary function and fetal status-monitor with PEFR or FEVl.
4.
Pharmacological therapy-in appropriate combinations and doses to provide baseline control and treat exacerbations. Compliance may be a problem, and periodic medication reviews are helpful (Sawicki, 2012).
In general, women with moderate to severe asthma ideally measure and record either their FEV1 or PEFR twice daily. The FEVl ideally is >80 percent of predicted. For PEFR, predicted values range from 380 to 550 L/min. Each woman has her own baseline value, and therapeutic adjustments can be made using this (American College of Obstetricians and Gynecologists, 2016a; Rey, 2007).