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.
“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.”
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.
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.
REFERENCE: Korb et al: Risk of severe maternal morbidity associated with cesarean delivery and the role of maternal age: a population-based propensity score analysis; http://www.cmaj.ca/content/191/13/E352.full