Friday, July 13, 2012

Near-miss maternal mortality

Maternal mortality has dropped 99% in the past 100 years. A maternal death is now, fortunately, a rare event. Attention, therefore, is shifting to maternal morbidity, in particular, life-threatening morbidity. The results of a new study are instructive.

Near-Miss Maternal Mortality: Cardiac Dysfunction as the Principal Cause of Obstetric Intensive Care Unit Admissions by Small et al. will be published in the February 2012 issue of Obstetrics and Gynecology. The title gives away the principle finding; heart disease is the most common cause of maternal ICU admission.

The study took place at Duke University from January 2005 to April 2011. There were 19,575 births and 5 maternal deaths for a maternal mortality rate of 25/100,000. That is approximately double the US maternal mortality rate, but that is only to be expected in a tertiary center that receives the most complicated cases from the surrounding area. There causes of the five maternal deaths were: two from metastatic cancer, two secondary to cystic fibrosis, and one the result of sepsis.

The authors then looked at maternal admissions to the intensive care unit:

Ninety-four obstetric patients—five per 1,000 deliveries—were admitted to ICUs. Eight declined participation in the study. Eighty-six patients were included in this analysis.

... African American women comprised the largest population admitted to the ICU (45%). Significant differences were found by race and ethnicity in the following variables: parity, BMI, and marital and insurance status. African American (mean 35) and Hispanic women (mean 36) had significantly higher BMIs than white women (mean 28). African American and Hispanic women were also more likely to have Medicaid or no insurance and were more likely to be unmarried and multiparous.
The following table shows the reasons for ICU admission.

The authors write:
... The leading admission diagnosis for pregnant and postpartum women was maternal cardiac disease (36%). Maternal hemorrhage (both obstetric and nonobstetric) was the second leading reason for admission (29%). Hypertensive disease accounted for 9% of ICU admissions...

The majority of cardiac conditions prompting ICU admission resulted from cardiomyopathy. Acute complications associated with peripartum cardiomyopathy
comprised the majority of this group. Congenital heart disease is the underlying etiology for many of these valvular lesions and cardiomyopathies. Congenitally
acquired conditions were the second leading cause of maternal cardiac ICU admissions...
The findings of this study are notable for the following:
  1. Race is a major risk factor for near-miss maternal mortality.
  2. Obesity (BMI greater than 30) is a major risk factor for near-miss mortality.
  3. The leading cause of near-miss mortality is cardiac disease.
  4. Infection and bleeding account for only one third of the near-miss events.
This paper demonstrates that near miss-maternal mortality, like maternal mortality, is the result of complex medical and non-medical factors. Both race and maternal BMI appear to play important roles. Pre-existing medical conditions account for a substantial proportion of near-miss maternal mortality. The traditional causes of maternal mortality and near-miss mortality have been eclipsed by cardiac complications of pregnancy.

In other words, contrary to the claims of natural childbirth and homebirth advocates, maternal mortality and near-miss maternal mortality are not related to obstetric interventions. The most common risk factor is pre-existing maternal health issues. Women with serious medical problems (including obesity) prior to pregnancy are the ones most likely to develop life threatening medical problems during pregnancy and childbirth.

This piece first appeared on The Skeptical OB in January 2012.

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