Detailed report on infant mortality neglects the most important detail

The new CDC report on infant mortality, Behind International Rankings of Infant Mortality: How the United States Compares with Europe, is an object example of how to deceive with statistics. It purports to be a detailed investigation of infant mortality, but it inexplicably fails to investigate the most important detail.

According to today’s article in the NYTimes:

High rates of premature birth are the main reason the United States has higher infant mortality than do many other rich countries, government researchers reported Tuesday in their first detailed analysis of a longstanding problem.

In Sweden, for instance, 6.3 percent of births were premature, compared with 12.4 percent in the United States in 2005, the latest year for which international rankings are available. Infant mortality also differed markedly: for every 1,000 births in the United States, 6.9 infants died before they turned 1, compared with 2.4 in Sweden. Twenty-nine other countries also had lower rates.

If the United States could match Sweden’s prematurity rate, the new report said, “nearly 8,000 infant deaths would be averted each year, and the U.S. infant mortality rate would be one-third lower.”

The use of this example highlights to disingenuousness of the authors. In their supposedly “detailed” report on infant mortality, they fail to analyze the most important detail: race. Unfortunately, African descent is a major risk factor for prematurity, and prematurity is a major cause of infant mortality. Therefore, it is hardly surprising that the US has a higher infant mortality rate than Sweden. The US has the highest proportion of women of African descent of any first world country. Sweden, of course, has virtually none.

The authors, however, seem more interested in jeering the US for its supposedly low standing in international comparisons than they seem in actually getting to the source of the problem. The report is filled with grim looking graphs that show how “poorly” the US fares when compared to other first world countries.

The first graph highlights the fact that the US is ranked 30th in the world for infant mortality. But the authors acknowledge that the US has a more comprehensive definition of infant mortality than other first world countries, many of which exclude the deaths of very premature infants even when they are born alive. The authors present a second graph adjusting for this discrepancy. In that more accurate graph, the US ranks 18th.

The authors mention the impact of race on prematurity, but they never adjust for it. The CDC Wonder website gives us access to the same database that MacDorman used in the study. Therefore, we can adjust for race. Doing so, would put the US 14th in the rankings.

The authors also mention assisted reproductive technology, but they don’t adjust for that either. The rates of twins, triplets and higher is greater in the US than in many European countries because of differing rates of assisted reproductive technologies and the difference in techniques.

The authors acknowledge that on an age specific basis, the US actually does better than almost all European countries. In other words, we are better at saving premature babies. Our relatively low ranking is the result of a higher rate of prematurity.

So our higher rate of infant mortality does not reflect poor medical care. It reflects factors beyond the control of doctors. Race is an uncontrollable factor; obstetricians and pediatricians have no control over assisted reproductive techniques. In fact, the data actually show obstetricians and pediatricians do a remarkable job of ensuring infant health.

Dr. MacDorman’s bias is most evident is her gratuitous swipe at obstetricians. According to the Times article:

Another factor in the United States, she said, is the increasing use of Caesarean sections and labor-inducing drugs to deliver babies early. The American College of Obstetricians and Gynecologists has guidelines stating that babies should not be delivered before 39 weeks without a medical reason, but doctors may be declaring a medical need more quickly than they did in the past.

“I don’t think there are doctors doing preterm Caesarean sections or inductions without some indications,” Dr. MacDorman said, “but there sort of has been this shift in the culture. Fifteen or 20 years ago, if a woman had high blood pressure or diabetes, she would be put in the hospital, and they would try to wait it out. It was called expectant management.

“Now I think there’s more of a tendency to take the baby out early if there’s any question at all.”

Dr. MacDorman neglects to mention that there is no evidence that such births are contributing in any way to the infant mortality rate. Indeed, the existing evidence suggests that these births actually save lives. During the time period when early deliveries increased, the rate of stillbirth dropped by 29%.

Infant mortality and prematurity are real and serious problems, and they won’t be solved by pretending they are simply medical problems. Infant mortality in general, and prematurity in particular, is the result of racial, social and economic disparities that must be investigated and addressed. MacDorman’s report risks obscuring this critical point in favor of castigating medical practitioners. Doctors are not responsible for the US ranking in infant mortality statistics, and therefore, they cannot fix it. If our goal is to prevent infant deaths, we must be honest about the real causes.