by Michael Smith

When cesarean section rates are lower than expected, adverse maternal or neonatal outcomes are higher, researchers said.

But the converse isn’t true — higher-than-expected C-section rates aren’t associated with a protective effect, according to Sindhu Srinivas, MD, of the University of Pennsylvania, and colleagues.

The finding comes from an attempt to see if the risk-adjusted C-section rate can be used as a marker for the quality of obstetric care, Srinivas and colleagues wrote in the May issue of Obstetrics & Gynecology.

The measure has been proposed previously, but has been criticized for including all deliveries — including those where it is medically necessary — and because the overall rate of C-sections had been rising.

Nevertheless, Srinivas and colleagues wrote, the risk-adjusted C-section rate is an attractive measure — it has “face validity, easy measurability, and construct validity.”

To evaluate the measure in the current climate, the researchers constructed a population-based cohort of 845,651 patients from 401 hospitals in California and Pennsylvania. They excluded premature births and those in which C-sections were standard of care (such as for malpresentation and cord prolapse).

As well as analyzing the overall cohort, the researchers looked separately at the 274,371 primiparous patients with full-term singleton pregnancies.

For both groups, they linked birth certificate and hospital admission records to estimate the correlation between risk-adjusted cesarean delivery and a composite of adverse maternal outcomes, adverse neonatal outcomes, and four obstetric patient safety indicators from the Agency for Healthcare Research and Quality (AHRQ).

The composite maternal outcome included such events as wound infection and postdelivery hemorrhage, and the composite neonatal outcome included such things as death and birth injury. The AHRQ indicators included such things as birth trauma and injury with cesarean delivery.

The researchers used logistic regression to calculate an expected rate of C-section for each hospital and compared that with the observed rate.

In both cohorts, there was a negative correlation between the C-section rate and each of the outcomes, which was significant except for one — AHRQ patient safety indicator 19 (injury with non-instrumented vaginal delivery).

Comparing C-section and adverse events rates showed that, in the general cohort:

* 59.8% of the 107 hospitals with lower-than-expected risk-adjusted C-section rates had a higher-than-expected rate of at least one of the six adverse outcomes.
* Only 19.6% of the 102 hospitals with higher-than-expected risk-adjusted C-section rates had a higher-than-expected rate of any of the six adverse outcomes.
* The comparable figure was 36.1% for the hospitals with the as-expected risk-adjusted C-section rates, which was statistically similar to the higher-than-expected group.

The pattern was similar in the primiparous subcohort, Srinivas and colleagues found.

“We speculate that, in some instances, patients benefit from having (cesarean) deliveries,” the researchers said, so that hospitals whose medical staff “do not act fast enough” to perform them may have a higher rate of adverse outcomes.

On the other hand, performing too many C-sections wasn’t associated with improved outcomes, they noted, adding that the finding “should not suggest” that the practice is desirable.

Instead, they said, “it likely reflects an overuse of medical care and the performance of unnecessary procedures.”

Srinivas and colleagues cautioned that they did not use primary chart abstraction to identify comorbidities and complications, opening the door to a misclassification bias.

They noted that it is also possible that some unobserved factors confounded the results. The observation does not prove a causal effect, they added.

Michael Smith is a MedPage Today North American Correspondent.

Originally published in MedPage Today. Visit MedPageToday.com for more obstetrics news.