Maternal Morbidity Greater With Cesareans, Especially in Over 35s

Tara Haelle

April 09, 2019

Women who give birth by cesarean section have significantly greater odds of severe acute maternal morbidity than those who have vaginal deliveries, even after excluding those with prenatal conditions and accounting for characteristics that increase the likelihood of a cesarean birth, according to a new case-control study published in the April issue of CMAJ.

"The excess risk was particularly marked for women older than 35 years and existed for cesarean deliveries both before and during labor in this subgroup," write Diane Korb, MD, MPH, of Paris Descartes University in France, and colleagues, but the association existed across all age groups older than 25 years.

"Our findings enhance the bulk of evidence that shows that although cesarean delivery is usually a safe intervention, it remains an invasive surgical procedure with intrinsic adverse effects for women," the researchers emphasize.

"These results have implications for clinical practice and will be useful in deciding the type of delivery," says Korb, an obstetrician, in a press release issued by CMAJ. "Physicians must consider this increased risk when determining the best way to deliver, especially for older mothers."

Rates of Cesarean Deliver Have Increased Dramatically in Last 20 Years

Rates of cesarean delivery have increased dramatically over the last 20 years, with more than one in five women delivering by cesarean, often for medically questionable reasons, say Korb and colleagues in their article. In the United States, cesarean delivery is now the most common surgery performed in hospitals, with about one in three babies delivered this way.

Despite clearly documented long-term obstetric risks associated with cesarean deliveries — such as uterine rupture and placental disorders — studies have not as clearly characterized short-term risks of cesarean versus vaginal deliveries, they note. Because most studies are observational, confounding by indication and other potential confounders may bias the findings.

The researchers analyzed data from a prospective population-based study called EPIMOMS involving mothers from six regions of France who gave birth at 22 weeks' gestation or later in 2012-2013.

Cases — all women who experienced severe acute maternal morbidity up to 42 days postpartum — were matched with a randomly selected 1/50 of 182,309 deliveries.

The researchers excluded women with severe acute antepartum morbidity, prenatal conditions such as placenta previa or preeclampsia, and those whose morbidity during labor necessitated an emergency cesarean delivery.

Maternal morbidity was defined as any of the following: admission to ICU, laparotomy after delivery, severe obstetric hemorrhage, eclampsia, severe preeclampsia, pulmonary embolism, stroke, psychiatric disorder, or hepatic, hematological, respiratory, cardiovascular, renal, or neurologic dysfunction.

Of 1444 cases, 36% of women had a cesarean delivery, compared with 18.2% of 3464 controls.

"Cesarean deliveries were more frequent among cases both either before labor (14.5% vs 8.5%) or during labor (21.5% vs 9.5%)," say Korb and colleagues.

Severe obstetric hemorrhage comprised 85.3% of cases, more than half of which (57.9%) occurred due to uterus atony.

Before adjustment, the following characteristics were significantly more likely among cases: sub-Saharan African maternal birthplace, older age, nulliparous or parous with at least one previous cesarean, living without a partner, higher body mass index, pre-existing maternal conditions, more previous obstetric hemorrhages, in vitro fertilization, multiple pregnancies, anemia, gestational hypertensive disorders, breech presentations, preterm deliveries, no prophylactic oxytocin after birth, and neonates larger for gestational age.

Don't Automatically Recommend Cesarean Deliveries for Older Mothers

The researchers then assigned mothers propensity scores based on their "probability of a cesarean delivery based on her individual covariates measured before delivery." They then matched 79.7% of mothers with cesarean deliveries (n = 917) to 24.4% of women with vaginal deliveries (n = 917).

Among these 1834 matched mothers, women with cesarean deliveries had a 1.8 greater odds of severe acute maternal morbidity than those who had vaginal births (adjusted odds ratio [aOR], 1.8).

The greater morbidity risk held for those aged 25-29 (aOR, 1.5), 30-34 (aOR, 1.6), and 35 and older (aOR, 2.9). Sensitivity analyses did not change the findings.

"Our finding raises questions about the practices of some obstetricians who may consider cesarean deliveries to be indicated by advanced maternal age, with the idea that there will probably be no further pregnancies," the authors write.

"This practice should be modified to avoid unnecessarily exposing women older than 35 years to the excess risk of severe acute maternal morbidity."

They caution, however, that their findings remain limited by the usual constraints of observational studies, including residual confounding and potential nongeneralizability to women outside of France. 

The research was funded by the National Research Agency and Île-de- France Regional Health Agency. The authors have reported no relevant financial relationships.

CMAJ. 2019;191:E352-60. Full text

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