Maternal and perinatal outcomes for nearly 30,000 pregnan cies in asthmatic women are shown in Table 51-2. Findings are not consistent among these studies. For example, in some, but not all, the incidences of preeclampsia, preterm labor, growth restricted infants, and perinatal mortality are slightly increased (Murphy, 2011). Other reports cited a small rise in the incidence of placental abruption and previa, preterm rupture of mem branes, and gestational diabetes (Getahun, 2006; Wang, 2014).
But, in a European report of 37,585 pregnancies of women with asthma, the risks for most obstetrical complications were not increased (Tata, 2007). Finally, Cossette and coworkers (2013) and increasing inhaled-corticosteroid dosage.
Increased morbidity appears to be signiicantly linked to severe disease, poor control, or both. In the study by the Maternal-Fetal Medicine Units (MFMU) Network, delivery before 37 weeks' gestation was not increased among the 1687 pregnancies of asthmatic women compared with those of 881 controls (Dombrowski, 2004a). But for women with severe asthma, the rate was increased approximately twofold. In a prospective evaluation of 656 asthmatic pregnant women and 1052 pregnant controls, Triche and coworkers (2004) found that women with moderate to severe asthma, regardless of treatment, are at increased risk of preeclampsia. Finally, the MFMU Network study suggests a direct relationship of baseline pregnancy FEV] with birthweight and an inverse relationship with rates of gestationl hypertension and preterm delivery (Schatz, 2006).
Maternal morbidity includes life-threatening complications from status asthmaticus. his causes muscle fatigue with respiratory arrest, pneumothorax, pneumomediastinum, acute cor pulmonale, and cardiac arrhythmias. Not surprisingly, maternal and perinatal mortality rates rise substantively when mechanical ventilation is required.
TABLE 51-2. Maternal and Perinatal Outcomes in Pregnancies Complicated by Asthma blncidence not significantly diferent compared with control group or generan l obstetrical population.
clncidence significantly greater than control group or general obstetrical population. NS = not stated.
As discussed, with reasonable asthma control, perinatal outcomes are generally good. In the Network study cited above, rates of adverse neonatal sequelae caused by asthma were not signiicantly increased (Dombrowski, 2004a). he caveat is that severe asthma was uncommon in this closely monitored group. When respiratory alkalosis develops, earlier animal and human studies suggest that fetal hypoxemia develops well before the alkalosis compromises maternal oxygenation (Rolston, 1974). It is hypothesized that the fetus is jeopardized by decreased uterine blood flow, decreased maternal venous return, and an alkaline-induced letward shit of the oxyhemoglobin dissociation curve (Chap. 47, p. 920).
The fetal response to maternal hypoxemia is decreased umbilical blood flow, increased systemic and pulmonary vascular resistance, and decreased cardiac output. Observations by Bracken and colleagues (2003) confirm that the incidence of fetal-growth restriction increases with asthma severity. Because the fetus may be seriously compromised as asthma severity increases, the need for aggressive management is underscored. Monitoring the fetal response is, in efect, an indicator of maternal status.