The treatment of asthma involves assessment and management from preconception to the postpartum period. Please refer to Table 11.3 and Figure 11.1 for a general overview of the classification and management of chronic asthma.

There are four general components of asthma care, irrespective of gestational age. These are (1) monitoring of respiratory status, (2) avoidance of possible triggers, (3) patient education, and (4) pharmacological treatment. Patients should get a baseline spirometry and be instructed in how to follow their peak expiratory flow rate (PEFR) at home. Ideally, this should be done twice a day in patients with persistent disease. Since pregnancy does not affect flow rates, reductions in these numbers usually indicate a worsening degree of airflow obstruction and should prompt quick medical evaluation. Second, it is critical that patients avoid their known triggers to asthma including tobacco, dust, extreme temperatures, and allergens such as pollen and pet dander. Third, patients need to be educated about their disease. Pregnancy constitutes a perfect window to educate women given the multiple contacts with providers increased motivation due to concerns for fetal well-being. Trigger control from washing bed sheets to vacuuming to rodent control are important strategies to review, especially since in most circumstances, women are more likely to be exposed to these triggers. Important topics that need to be reviewed also include inhaler technique, early recognition of symptoms of worsening asthma, an action plan for acute asthma exacerbations, as well as an overview of how poorly controlled asthma can affect the pregnancy. Patients should also be provided with the opportunity to express their concerns and ask questions. In a multi-institutional prospective study, lower forced expiratory volume in 1 s (FEV1), but not asthma symptom frequency, was shown to be associated with adverse perinatal outcomes [9]. These data may be a reflection of the effect of asthma severity or poor asthma control on perinatal outcomes and emphasize the possibility of discrepancies between symptom-based assessment and more objective measurement of lung function in pregnant women with asthma. Finally, women with asthma need to receive the appropriate pharmacological treatment to achieve disease control. Population-based data do show that well-controlled asthmatics without exacerbations have better outcomes than women with exacerbations, but for obvious reasons, there are no randomized controlled trials evaluating this particular question. Although most clinical practices use symptom-based, guideline-directed assessments to decide on medication use, recent data from a randomized controlled trial suggest lower rates of exacerbation, improved quality of life, and reduced neonatal hospitalization when management decisions were based on measurements of exhaled nitric oxide in pregnancy [10]. It is likely that this improvement in outcomes is due to improved control, rather than the method of assessment itself.

Table 11.2 provides an overview of the asthma medications that are used in pregnancy. As in the nonpregnant population, the choice of pharmacological agent depends on disease severity. A frank discussion with the expectant mother and her partner should occur to encourage them to voice their concerns regarding asthma treatment in pregnancy. Most women are told to stop their inhalers at the time of pregnancy diagnosis because of FDA category listing. For that reason, a good amount of time should be spent on counseling about the use of asthma drugs in pregnancy. Explaining to women that asthma control is key to the health of the pregnancy and their baby is an important part of counseling and may have to be done repeatedly during the course of pregnancy. In general, most asthma medications are justifiable in pregnancy, and some have adequate safety data. As noted in Table 11.2, many of the drug choices are category C according to the FDA classification; however, these drugs are used routinely in the care of pregnant women with asthma. In addition, although leukotriene inhibitors are listed as category B, safety data are less reassuring than other drugs classified as category C. Omalizumab is classified as category B by the FDA despite the fact that all of the initial trials have excluded pregnant women. These safety data are based on animal studies which are limited by the fact that teratogenicity may be species specific. In addition, although prednisone may be associated with a small risk of cleft palate when administered in early pregnancy, the benefit of this drug in an acute exacerbation of asthma by far outweighs the small risk of malformation. Table 11.3 reviews the classification of asthma severity, which includes not only symptoms but also peak flow meter measurements.

Other coexisting diseases may worsen asthma and may have to be treated in order to achieve optimal control. The most common of these disorders are allergic rhinitis, gastroesophageal reflux disease (GERD), sleep apnea, and psychiatric illnesses. Allergic rhinitis occurs in 80–90 % of nonpregnant asthmatics and worsens asthma symptoms. Management of the allergic rhinitis with drugs such as steroidal nasal sprays often improves asthma symptoms. Women who are pregnant can also develop a different form of rhinitis, called rhinitis of pregnancy. This typically occurs in the latter part of pregnancy and resolves completely within 2 weeks after delivery.

The prevalence of GERD among nonpregnant asthmatics varies between 30 and 90 %. In pregnant women with asthma, this number is likely higher given that GERD has been reported to be present in nearly 75 % of all pregnant women [11]. GERD can worsen bronchoconstriction via increased vagal tone, heightened bronchial reactivity, and microaspiration of gastric contents into the upper airway. Patients who have symptoms of GERD benefit from treatment. Although proton pump inhibitors are not expected to increase the risk of congenital malformation in experimental animal studies and limited human pregnancy exposures, ranitidine constitutes a safer first choice. Finally, asthma and psychiatric comorbidities may coexist. Stress and mental illness can worsen asthma in the pregnant women and may also complicate compliance.

During labor, the general management of asthma is not significantly different than above. Most patients with asthma do not require a labor and delivery plan. However, patients with more severe disease or those who suffered an exacerbation close to term would require a detailed plan. Stress dosing with steroids during labor can be considered in patients who have been on prolonged periods of systemic steroids during the pregnancy. Patients with active symptoms or more severe asthma may benefit from regional anesthesia. Epidural anesthesia reduces minute volume and oxygen consumption and may help prevent hyperinflation in patients with active symptoms and reduce oxygen consumption. If general anesthesia is to be considered, then ketamine and halogenated anesthetics are preferred. It is safe to use oxytocin and prostaglandin E2. However, ergotamine and ergot derivatives, 15-methyl prostaglandin F2 alpha, morphine, and meperidine should be avoided in pregnant women with asthma as they may be associated with an increased risk of bronchospasm.

An overview of the management of acute asthma exacerbations in the pregnant woman is detailed in Fig. 11.2. More detailed information can be found in National Heart Lung and Blood Institute guidelines on asthma and pregnancy published in 2004. The treatment is similar to nonpregnant women with a few key differences that need to be highlighted. The first is to remember that during pregnancy, the normal PaCO₂ is lower than in the nonpregnant state. Therefore, a normal or high PaCO₂ heralds worsening respiratory failure and should be acted upon quickly. Second, hypoxia during asthma exacerbations can lead to fetal distress and decelerations. Therefore, immediate bronchodilators and supplemental oxygen should be administered. Finally, it should be noted that while the indications for airway intubation are the same in the pregnant asthmatic as the nonpregnant asthmatic, intubation during pregnancy, especially in the third trimester, can be more difficult. This is due to increased airway edema, low FRC and oxygen reserve, and a more profound response to sedatives from decreased venous return. Hence, the most experienced member of the team should perform the intubation and be familiar with difficult airway management procedures. Airway intubation is discussed in more detail in the critical care Chap. 2.

Pneumonia is one of the leading causes of non-obstetric maternal deaths in the United States [12]. There are several categories of pneumonia based on the likely spectrum of pathogens: community-acquired pneumonia (CAP), healthcare-associated pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia as well as pneumonia in the immune-compromised host. As pregnant women are usually young and healthy, CAP predominates.

General supportive measures are similar in patients with various types of pneumonia. For patients with a viable fetus who require admission, the obstetric team should be consulted for fetal monitoring as well as timing of delivery in the event of fetal distress. Hypoxia, acidosis, and fever should not be tolerated as they are independently associated with poor fetal outcomes. Oxygen should be supplemented for goal saturations > 95 % or PaO₂ above 70. Fever should be treated aggressively for a goal temp of less than 38 °C.

In cases of severe pneumonia associated with respiratory failure, early intubation should be considered. Intubations in pregnancy have a higher failure rate than the general surgical population (see Chap. 2 on airway intubation). Attempts to maintain CO₂ within an acceptable range may be challenging in the event of acute respiratory distress syndrome (ARDS) and the use of lung protective strategies. Low tidal volume ventilation strategy with a target tidal volume of 6 ml/kg is recommended for ARDS [23]. Though pregnant women were excluded in the acute respiratory distress network studies on lung protective strategies, low tidal volume ventilation should be attempted, initially with a higher respiratory rate to maintain ventilation given the survival benefit observed in the nonpregnant population. However, higher tidal volumes may be required to correct acidosis that may compromise the fetus, in such instances attempts should still be made to keep the plateau pressure below 30 cm of water as barotrauma is thought to contribute significantly to lung injury. PaCO₂ levels need to be watched closely, and given the 10 mmHg gradient between fetal and maternal, maternal PaCO₂ should be kept at 55 mmHg or lower. Use of bicarbonate to correct the PH has been suggested in the nonpregnant population though clinical studies to support this approach are limited. It is thought that the transfer of bicarbonate across the placenta is slow and may not be adequate to correct fetal acidosis. While the decision to admit patients to the ICU is complex and should be individualized, clinicians should have a lower threshold when evaluating pregnant mothers.