Perinatal mortality combines fetal and neonatal deaths and is one measure of healthcare quality before, during, and after delivery. Fetal mortality data from the National Vital Statistics system are usually presented for fetal deaths after the 20-week threshold. Using this threshold, the numbers of fetal deaths in the United States in 2013 slightly surpassed numbers of neonatal deaths when considering fetal deaths beyond 20 weeks (Fig. 35-1) (MacDorman, 2015a).
Distribution of fetal and neonatal deaths in the United States, 2013. (Data from MacDorman, 2015a.)
As discussed in Chapter 1 (p. 3), the current definition of fetal death adopted in the United States by the National Center for Health Statistics is based on one recommended by the World Health Organization (MacDorman, 2015a). It states that “Fetal death means death prior to complete expulsion or extraction from the mother of a product of human conception irrespective of the duration of pregnancy and which is not an induced termination of pregnancy. The death is indicated by the fact that after such expulsion or extraction, the fetus does not breathe or show any other evidence of life such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles. Heartbeats are to be distinguished from transient cardiac contractions; respirations are to be distinguished from fleeting respiratory efforts or gasps.”
Reporting requirements for fetal deaths in the United States are determined by each state, and thus criteria differ. Most states mandate reporting of deaths of fetuses that are 20 weeks’ gestation or older or have a minimum birthweight of 350 g, which roughly equates to that at 20 weeks—or a combination of both. However, evidence shows that not all required fetal deaths are reported, especially at earlier gestational ages (MacDorman, 2015a).
Similarly, comparisons of rates among countries are limited by incomplete fetal death data. Internationally, less than 5 percent of neonatal deaths have formalized documentation (Lawn, 2016). Further, comparative analyses using birthweight versus gestational age among countries yield discordant results. In the United States, if stillbirth were defined by a birthweight ≥500 g, the stillbirth rate would be reduced by 40 percent compared with a 20-week-age defined cohort (Blencowe, 2016).
Three fetal mortality epochs are generally recognized. Early describes deaths before 20 completed weeks’ gestation; intermediate for those between 20 and 27 weeks; and late for those ≥28 weeks. The fetal mortality rate in each epoch has changed little since 2006. As shown in Figure 35-2, fetal death rates are highest at the earliest and latest gestational ages, which suggests etiological differences.
National Vital Statistics Report: fetal mortality rate per 1000 births by weeks’ gestation. (Data from MacDorman, 2015a.)