Wednesday, October 7, 2009

Descriptive studies & routine fetal monitoring

Sometimes the birth-related stuff shows up where I don't expect it. From an article for my research methods class tomorrow:

"...Another sad example in which misinterpretation of descriptive studies* hurt public health is routine electronic fetal monitoring in labour. A quarter of a century ago, temporal associations between the introduction of electronic fetal monitoring and falling perinatal mortality rates led to the conclusion that continuous fetal heart rate monitoring was a good thing. Moreover, authorities of the day predicted a 50% reduction in perinatal morbidity and mortality from its use.

Based on this rosy assessment from prominent obstetricians, this expensive and intrusive technology took obstetrics by storm. However, the initial upbeat
assessment did not survive scientific scrutiny. Years later, a meta-analysis of the randomised controlled trials showed that, by comparison with routine intermittent auscultation, routine electronic fetal monitoring confers no lasting benefit to infants, whereas it significantly increases operative deliveries; thus harming women.

Based on objective reviews, both the Canadian Task Force on the Periodic Health Examination and the US Preventive Services Task Force have given routine electronic fetal monitoring a D recommendation (fair evidence against its routine use). Despite this advice, about three-fourths of all births in the USA include electronic fetal monitoring. Failure to appreciate the limitations of descriptive studies has caused lasting harm and squandered billions of dollars."

*The authors define a descriptive study as "concerned with and designed only to describe the existing distribution of variables, without regard to causal or other hypotheses." An example of descriptive studies is early reports of AIDS, describing clusters of unusual cases and generating hypotheses as to their cause(s).

Citation: Grimes DA, Schulz KF. "Descriptive studies: what they can and cannot do". Lancet. 2002. 359:145-49.

(H/t to my roommate and classmate Katie, who found this passage and suggested I might want to get on that class reading!)

No comments: