4. Preexistent chronic disorders, often indirectly affecting pregnancy

This chapter describes the impact of chronic disorders that do not directly interfere with placental development and function, but often have an indirect negative effect on the course and outcome of pregnancy. The most important primary organs targeted by these disorders are lungs (sect. 4.1), GI-tract (sect. 4.2), liver (partly) (sect. 4.3), endocrine system (sect. 4.4) and blood (sect. 4.5). The final two sections describe the interaction of common psychiatric disorders with pregnancy (sect. 4.6) and the effect of pregnancy on the pharmacokinetics of frequently used medication (sect. 4.7). The adverse effects of these disorders on pregnancy are partly related to the impaired function of the chronically affected organs (such as reduced respiratory reserve capacity in women with severe asthma), and partly related to their negative effect on the cardiovascular and metabolic reserves normally available to accommodate pregnancy. These two features lower the threshold for activation of the stress response as detailed in Chaps. 1 and 2. Early activation of this stress response not only predisposes a pregnancy to preterm birth and/or placental dysfunction. It may also worsen the underlying chronic disorder and with it, indirectly amplify the stress response and its associated adverse effect on pregnancy. These inferences indicate that optimizing clinical management of the disorder prior to pregnancy can be expected to reduce the risk of these negative effects.