he frequency ofplacental abruption has risen in this country, and most ofthis increase is in blackwomen (Ananth, 2005, 2016). At Parkland Hospital, however, the frequency ofsevere abruption has declined. This discrepancy may be explained in part by the variations in management ofearly-onset preeclampsia (Chap. 40, p. 728). Specifically, with placental abruption so extensive as to kill theetus, the incidence was 0.24 percent or 1 in 420 births from 1956 through 1967 (Pritchard, 1967). As the number of high-parity women giving birth declined along with improved availability of prenatal care and emergency transportation, the frequency of abruption causing fetal death dropped to 0.12 percent through 1989 in our obstetrical population. And, most recently through 2015, it declined to 0.05 percent or 1 in 2060.
Overall, perinatal outcomes are influenced by gestational age, and the frequency of placental abruption rises across the third trimester. As seen in Figure 41-17, more than half of the placental abruptions at Parkland Hospital developed at gestational ages ::37 weeks. Perinatal mortality and morbidity, however, are more common with earlier abruptions (Furukawa, 2015a). Ofother related factors, major fetal congenital anomalies have greater association with placental abruption (Riihimaki, 20l3).
Although the rates of fetal death have declined, the contribution of abruption as a cause of stillbirth remains prominent because other causes have also decreased. For example, since the early 1990s, 10 to 12 percent of all third-trimester stillbirths at Parkland Hospital have been the consequence of placental abruption. Others have documented high perinatal mortality rates caused by placental abruption. Salihu and colleagues (2005) analyzed more than 15 million singleton births between 1995 and 1998. The perinatal mortality rate associated with placental abruption was 11r9 per 1000 births compared with 8 per 1000 for the general obstetrical population.
22.7
FIGURE 41-17 Frequency of placental abruption by gestational age at Parkland Hospital.
Neonatal deaths are common following placental abruption.
At Parkland Hospital, 15 percent ofliveborn neonates died. Perinatal morbidity-oten severe-is also common in surviving newborns (Abdella, 1984). Studies by Matsuda and coworkers (2003, 2013) reported that 20 percent of survivors developed cerebrl palsy. These observations are similar to ours from Parkland Hospital. Notably, 20 percent ofliveborn neonates ofwomen with an abruption had severe acidemia, deined by a cord arterial blood pH <7.0 or base deficit of::12 mmollL. One review conirmed the associated risk for cerebral palsy (Downes, 2017). Even so, nanth and coworkers (2017) attribute adverse neurodevelopmental outcomes to be largely attributable to preterm delivery.
Several predisposing factors raise the risk for placental abruption, and some are listed in Table 41-4.Advancing matenalage is one, although data are conlicting regarding women of reat pariy
TABLE 41 -4. Risk Factors for Placental Abruption
Increased age and parity 1.3-2.3
Preeclampsia 2.1-4.0
Chronic hypertension 1n.8-3.0
Chorioamnionitis 3.0
Preterm ruptured membranes 2.4-4.9
Low birthweight 14.0
Cigarette smoking 1.4-1.9
Single umbilical artery 3.4
NA = not available.