Finally: a comprehensive analysis of US infant mortality

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I’ve been writing about this problem for many years: no, not the high US infant mortality rate, but the refusal to address the most important causes of high US infant mortality.

Five years ago, in November 2009, I wrote in 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 [by MacDorman et al], 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…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.

And last year in The March of Dimes and dishonesty about prematurity, I wrote:

The March of Dimes has chosen to misrepresent prematurity as being caused by early elective delivery. While early elective delivery poses risks, it also has significant benefits (reducing the stillbirth rate) and, in any case, is only a tiny contributor to the problem of prematurity…

The MOD has been publishing a yearly “report card” on prematurity. The report card is rather farcical since while claiming to grade states on prematurity rates, it is basically grading them by the proportion of African-Americans in each state.

Finally, someone has analyzed the US infant mortality rate with the object of improving it, as opposed to using it for selfish ends. The new paper, Why is infant mortality higher in the US than in Europe?, is written by Professor Emily Oster and colleagues. Oster is the author of Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know.

Oster et al. lay out the dimensions of the problem:

In 2013, the US infant mortality rate (IMR) ranked 51st internationally, comparable to Croatia, despite an almost three-fold difference in GDP per capita.1 One way to quantify the magnitude of this infant mortality disadvantage is to consider that the US IMR is about 3 deaths per 1000 greater than Scandinavia…

While the US IMR disadvantage is widely discussed and quantitatively important, the determinants of this disadvantage are not well understood, which hinders policy efforts aiming to reduce the US infant mortality rate. A key constraint on past research has been the lack of comparable micro-datasets across countries. Cross- country comparisons of aggregate infant mortality rates provide very limited insight, for two reasons. First, a well-recognized problem is that countries vary in their reporting of births near the threshold of viability. Such reporting differences may generate misleading comparisons of how infant mortality varies across countries. Second, even within a comparably reported sample, the observation that mortality rates differ one year post-birth provides little guidance on what specific factors are driving the US disadvantage.

In other words, as I’ve written countless times over the years, direct comparisons of national infant mortality rates are invalid because the US includes very premature babies born alive, while many other countries do not. Since the highest death rates are in very premature babies, failure to include them makes other countries’ infant mortality rates look far better than they really are.

How did Oster et al. address this problem?

… We combine US natality micro-data with similar data from Finland, which has one of the lowest infant mortality rates in the world, and Austria, which has similar infant mortality to much of continental Europe. We first provide a detailed accounting of the US IMR disadvantage, quantifying the importance of differential reporting, conditions at birth (that is, birth weight and gestational age), neonatal mortality (deaths in the first month), and postneonatal mortality (deaths in months 1 to 12)… Second, we provide new evidence on the demographic composition of the US IMR disadvantage.

What did they find?

… Differential reporting of births near the threshold of viability can explain up to 40% of the US infant mortality disadvantage. Worse conditions at birth account for 75% of the remaining gap relative to Finland, but only 30% relative to Austria. Most striking, the US has similar neonatal mortality but a substantial disadvantage in postneonatal mortality. This postneonatal mortality disadvantage is driven almost exclusively by excess inequality in the US: infants born to white, college-educated, married US mothers have similar mortality to advantaged women in Europe. Our results suggest that high mortality in less advantaged groups in the postneonatal period is an important contributor to the US infant mortality disadvantage.

First, nearly half the differential in infant mortality is due to failure of other countries to include extremely premature babies born alive.

Second, the disparity in infant mortality (death from birth to one year) has little if anything to do with obstetric care since US neonatal mortality (death from birth to 28 days) is similar to other industrialized countries.

Third the disparity in post neonatal mortality is attributable to race and socio-economic status.

In other words, while birth activists, including CDC statistician Marian MacDorman, who is also (surprise!) the Editor of the Lamaze journal Birth: Issues in Perinatal Care, and organizations like the March of Dimes have been wailing about American obstetric care in general, and early elective induction in particular, the relatively high US infant mortality has nothing to do with American obstetric care in general, and early elective induction in particular.

Which raises the question why the people supposedly concerned with reducing the infant mortality rate haven’t bothered to address the real causes of US infant mortality. It appears they don’t really care about infant mortality and prematurity beyond using it as a cudgel to chastise American obstetricians. The tragedies of women of color, and poor women are exploited to serve the ends of birth activists, not to improve the outcomes for those who suffer. The poor infant mortality rate is used as a slogan to increase market share and profits for midwifery among Western, white, well off women, the demographic most likely to choose midwifery services. The victims of high US infant mortality are left to fend for themselves.