Severe maternal morbidity, in plain words
A list of 21 life-threatening events at delivery. It affects roughly one to two hospital deliveries in a hundred, and most of that is blood transfusion.
You will meet the phrase "severe maternal morbidity" in the news. It is a technical term, not a diagnosis, and knowing what it contains changes how it reads.
CDC's definition: Severe maternal morbidity (SMM) includes unexpected outcomes of labor and delivery that can result in significant short- or long-term health consequences.
CDC finds it in hospital records using a set of diagnosis codes: These 21 indicators and corresponding ICD codes can identify delivery hospitalizations with SMM using administrative data starting in October 2015.
The single most important thing to know. The measure is dominated by blood transfusion. That is why researchers routinely report it twice, with and without transfusion counted, and the two numbers differ by roughly a factor of two.
| Study and database | Period | Counting rule | Per 10,000 hospital deliveries |
|---|---|---|---|
| National Inpatient Sample and state databases | 2012 to 2019 | Transfusion excluded | 69.5 to 79.7 |
| Nationwide Readmissions Database | 2016 to 2022 | Transfusion excluded | about 70 to about 100 |
| Nationwide Readmissions Database | 2016 to 2022 | Transfusion included | about 150 to about 220 |
| Premier all-payer database | 2008 to 2021 | Transfusion included | 146.8 to 179.8 |
Put in words: roughly 1.5 to 2 hospital deliveries in every 100 when transfusion is counted, and roughly 0.7 to 1 in every 100 when it is not. All three studies show the same direction of travel.
And alongside that rise, in the same Premier data: deaths during delivery-related hospitalizations fell from 10.6 per 100,000 in early 2008 to 4.6 per 100,000 in late 2021. Severe events rose; deaths fell.
despite 50 years of effort by national, international, and professional organizations, determining the ideal SMM measure remains a work in progress.There is also a technical break in the record: the US changed diagnosis coding systems in October 2015, and one analysis showed the change alone moved five of twenty indicator rates. Any trend line crossing that date carries that problem with it.
"Does that statistic include blood transfusion, or not?"
"Which of these things would actually apply to me?"