Infant mortality rate as a metric for best gestational age for delivery

The title of the recent publication by Rosenstein et al “The mortality risk of expectant management compared with delivery stratified by gestational age and race and ethnicity” represents a significant error by conflating infant mortality rates with prospective mortality risks. Although it has been reported for some time, only recently has the National Center for Health Statistics validated what it termed the prospective fetal mortality risk . In doing so, 2 fundamental facts become clear: (1) given that only women who are still pregnant are at risk for stillbirth, the prospective fetal death risk is calculated based on the proportion of ongoing pregnancies and not based on the number of deliveries that occur at any given week of gestation (fetal death rate); and (2) although the fetal death rate decreases beyond 36 weeks’ gestation, the prospective risk of fetal death increases dramatically. Rosenstein et al got this part of their analysis right.

However, much of the article’s conclusions are based entirely on comparisons of the fetal death risk to infant mortality rates. Infant mortality rates have been shown to demonstrate the same arithmetic characteristics as fetal death rates at term, namely, higher at earlier gestations and lower as gestational age advances owing to the much greater number of births that occur. But by an examination of the actual number of infant deaths, much greater numbers of infant deaths occur as gestational age advances ( Figure ). Moreover, the most common causes of infant death at term (after excluding congenital anomalies, which is the most common cause) are sudden infant death syndrome, homicide, influenza, and pneumonia, which are all entities with no plausible causal relationship to birth at 37, 38, or 39 weeks’ gestation.

May 6, 2017 | Posted by in GYNECOLOGY | Comments Off on Infant mortality rate as a metric for best gestational age for delivery

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