The stillbirth frequency with chronic hypertension is substantively greater in most reports (Chap. 35, p. 646). In the Nationwide Patient Sample study, the stillbirth rate was 15.1 per 1000 births (Bateman, 2012). This is similar to that of 18 per 1000 from a Norwegian study by Ahmad and coworkers (2012) and of 24 per 1000 births from a Network study reported by Ankumah and colleagues (2014) and described on page 982. Low-birthweight neonates are also common. hey are due to fetal-growth restriction, preterm delivery that is largely clinically indic�ted, or both (see Fig. 50-3). In the California database study noted earlier, a fourth of fetuses were delivered preterm (Yanit, 2012).
These and other studies attest to the elevated risk for fetalgrowth restriction, and the incidence averages 20 percent. Zetterstrom and coworkers (2006) reported a 2.4-fold risk for fetal-growth restriction in 2754 chronically hypertensive Swedish women compared with the risk in normotensive women. Broekhuijsen and associates (2012) found a 1.3-fold increased risk for 1609 Dutch nulliparas with chronic hypertension compared with that in normotensive controls. As with other complications, fetal-growth dysfunction is more likely in chronically hypertensive women who develop superimposed preeclampsia. In one study, the incidence of growth-restricted fetuses born to women with superimposed preeclampsia was almost 50 percent compared with only 21 percent in chronically hypertensive women without preeclampsia (Chappell, 2008). Finally, women with chronic hypertension severe enough to warrant treatment had an II-percent incidence of fetal-growth restriction to a degree yielding birthweights ;3rd percentile (Morgan, 2016a). For all of these reasons, neonates born to these women have a correspondingly high rate of intensive-care nursery admission.
All of these adverse perinatal efects of chronic hypertension contribute to the greater perinatal mortality rate, which is threeto fourfold higher than the rate in nonafected gravidas (American College of Obstetricians and Gynecologists, 2013). In the Network study by Ankumah (2014) referenced in Figure 50-3, the perinatl death rate was 31 per 1000 births with mild hypertension, 72 per 1000 births with moderate disease, and 100 per 1000 births in women with severe chronic hypertension. And, in the study from Parkland Hospital by Morgan (20 16a), the perinatal mortality rate was 32 per 1000 births in women who were treated for their chronic hypertension. Again, as expected, the highest rates are in women who develop superimposed preeclampsia, for whom the risk doubled from 4 to 8 percent. Finally, if diabetes coexists with chronic hypertension, then preterm delivery, fetalgrowth restriction, and perinatal mortality rates are increased even more (Gonzalez-Gonzalez, 2008; Yanit, 2012).