A New England Journal of Medicine article this month discusses outcomes for babies born by elective repeat cesarean section. Here is a link to a New York Times article about the study.
In this study, data on 19 university hospitals was taken from the Eunice Kennedy Shriver National Institute of Child Health and Human Development cesarean registry. The investigators looked at 28,867 patients with prior cesarean sections who had repeat cesarean sections. Patients who had cesareans before 37 weeks were excluded from the study. Those who were in labor or already had spontaneous rupture of membranes were also excluded.
Then, for each case, the investigators determined the reasons for the cesarean section. Only cesareans without a medical reason were considered elective.
Some of the reasons they found were:
multiple gestations
non vertex presentation
major malformations
maternal medical problems such as heart disease or HIV
prior uternie incision that was not low transverse
non-reassuring fetal heart tracing or fetal testing
suspected macrosomia (abnormally large baby)
placenta previa or abruption
There were 13,258 elective repeat cesarean sections done after 36 weeks (46% of all repeat cesarean sections).
Distribution of elective repeat cesarean sections by gestational age:
37 weeks 834 pts 6.3% of all elective cesareans
38 weeks 3909 29.5%
39 weeks 6512 49.1%
40 weeks 1385 10.4%
41 weeks 505 3.8%
>= 42 weeks 113 0.9%
Then the investigators tracked the babies' outcomes.
They looked for:
death
breathing problems
hypoglycemia
severe newborn infection
seizures
hypoxis ischemic encephalopathy
CPR
signs of severe stress
admission to the neonatal ICU
hospitalization for 5 days or more
They found that babies born by elective repeat cesarean section before 39 weeks were at higher risk for having these problems.
babies born at:
37 weeks 15.3% had problems had 2.1 times the risk of problems compared to 39 weeks
38 11.0% 1.5
39 8.0% ----
40 7.3% 0.9
41 11.3% 1.4
>=42 19.5% 2.5
The researchers concluded from their study two things.
So, what does all this mean to a pregnant woman trying to make decisions?
If there are no medical problems, this study suggests that she can minimize the risk of problems with baby by scheduling the cesarean section after reaching 39 weeks.
In real life, however, there are two situations I can think of that make it difficult to apply this study. First, if a woman really wants an elective repeat cesarean section, how does she know she isn't going to go into labor before 39 weeks? There would be pressure to have a cesarean section sooner rather than later to make sure she was really going to get an elective repeat cesarean section. This is the sort of decision that may seem easy for those of us who are not pregnant but can be excruciating for women who are.
Second, this study was based on trained reviewers looking at medical records. Unrecorded conversations between providers and patients may include soft indications. For example, if I tell a mother that baby feels big, I haven't officially diagnosed macrosomia on the record, but I implied it to the mother. This may be the final straw for a woman to decide on an early repeat cesarean. In this study, her case would still be considered an elective repeat cesarean section. The woman, however, may feel her cesarean is medically indicated. She may feel it is better to have the cesarean earlier than 39 weeks to avoid having a big baby. This study suggests that by doing this, the baby will be at increased risk for complications. Given the known inaccuracies of predicting birth weight, I think using the possibility of a big baby as a medical indication for cesarean section before 39 weeks is problematic but more common than suggested by this study.
