This retrospective cohort study of antepartum elective or non-indicated C-section at a large obstetric center in Porto Alegre, Brazil, demonstrates that compared with deliveries at or after 39 weeks, earlier deliveries were significantly associated with NICU hospitalization, neonatal hyperbilirubinemia and respiratory distress.
The increasing rate of elective C-sections have motivated similar studies around the world, seeking to establish which gestational age is associated with less adverse outcomes for mothers and newborns. Overall, the conclusion is that surgical deliveries without clinical indication do not bring any maternal or fetal benefit, but increases risks for both (18).
A prospective multicenter study by Villar et al. (19) for the World Health Organization found a significantly higher risk of mortality and severe neonatal morbidity in C-section when compared to vaginal delivery, regardless of gestational age. The risk, however, decreased when the cesarean section is preceded by labor. The lack of labor affects the physiological process of onset of breathing, as there is no mechanical compression of the lungs necessary to facilitate postnatal pulmonary adaptation. This justifies the greater occurrence of transient tachypnea among newborns with elective surgical delivery.
Despite some limitations, our results are consistent with previous large population studies that showed that performing elective C-section before 39 weeks of gestation leads to a higher overall risk of adverse neonatal outcomes (20-23). In contrast, Wilmink et al. (2010) found a higher risk of neonatal complications with C-section at 41 weeks or later (22). Chiossi et al. identified that 39 weeks is an optimal timing of delivery, when comparing delivery at each gestational age (24), also supporting our findings. In Tita et al. (2009), the risk attributable to elective delivery before 39 weeks was 48% for 37 weeks of gestational age and 27% for 38 weeks - this means that postponing elective delivery until 39 weeks decreased cases of the primary outcome by 48% (which included, among others, death, sepsis, hypoglycemia, respiratory dysfunction and admission to a neonatal ICU) in relation to cesarean section at 37 weeks (21).
It is a consensus that even after reaching the term (gestational age of 37 weeks), the risk of adverse neonatal events decreases with each additional week up to 39 weeks (21, 22, 23, 25). This is one of the main reasons for guidelines to defend the postponement of elective C-section in low-risk pregnancies to at least 39 weeks of gestation, in addition to corroborating the division in early term (37 to 38 weeks and 6 days); full term (39 to 40 weeks and 6 days) and late term (41 to 41 weeks and 6 days) (26).
In a study by Doan et al (27), comparing fetal outcomes between early term and full term after elective cesarean section, the rate of neonatal adverse outcomes decreased significantly with increasing gestational age. Birth between 37 and 38 weeks and 6 days presented 2 times more risk (OR 2.40, 95%CI 1.58-3.66) for severe respiratory dysfunction; 3 times more risk of jaundice (OR 3.62, 95%CI 2.22-5.92) and 1.8 times more risk of hypoglycemia (OR 1.80, 95%CI 1.06-3.05). This demonstrated that, even after reaching term, neonatal outcomes continue to improve with increasing gestational age up to 41 weeks. In a classic study by Zanardo et al (28), there was a significant decrease in the risk of resuscitation or orotracheal intubation for elective C-sections performed after 38 weeks of gestation when compared to those performed between 37 weeks and 37 weeks and 6 days. In a large retrospective Chinese cohort (29), NICU admission rates were significantly higher (OR 3.73, 95%CI 2.84-4.89) in newborns with elective cesarean section at a gestational age of 37 weeks when compared to those at 39 weeks. A similar trend of increase risk with lower gestational age was found in relation to neonatal infection (OR 3.68, 95%CI 1.80-7.52), adverse respiratory outcome (OR 4.82, 95%CI 3.35-6.94), hypoglycaemia (OR 3.85, 95%CI 2.29-6.48), hyperbilirubinemia (OR 3.50, 95%CI 2.12-5.68) and prolonged hospital stay (OR 7.51, 95%CI 5.10-11.07). We found similar data in our study, showing reduction on odds of NICU admission, respiratory distress and hyperbilirubinemia with higher gestational ages.
The risk of stillbirth with increasing gestational weeks is an important concern for choosing the optimal time of elective C-section at term. Previous studies have not shown an increase in stillbirths after 39 weeks of gestational age (30, 31). In our study, the stillbirth rate was not evaluated because of study design limitations.
Neonatal and maternal mortality is a severe violation of the reproductive rights of women, since it could be prevented with efficient and early care (32). Studies of the timing of elective C-section sometimes involve medical and obstetric indications, which bias the conclusion about elective C-section before or after 39 gestational weeks.
Brazil is a country with high rates of C-sections and there is a significant difference in this index when comparing private and public hospitals. In supplementary health, the cesarean rate is 80-90%, while in the public sector it is 35-45% (33, 34, 35). In our country, C-sections are more frequent among white women, with more years of schooling and from higher socioeconomic groups (19). In the private sector, cesarean rates are extremely high in women at low obstetric risk, indicating the occurrence of the procedure without any clinical indication. Nakamura et al. found great difference in low-risk preterm rates when comparing the paying source: 25.4% in the public sector and 71.4% in the private, which raises the question of whether elective C-sections are causing iatrogenic prematurity (35). This corroborates the determination of a minimum gestational age for performing elective surgical delivery, aiming mainly to reduce morbidities associated with prematurity in newborns.
Our findings are consistent with those in the international medical literature. In our study, admission to the neonatal ICU, respiratory distress and hyperbilirubinemia were more frequent when the elective C-section was performed at a gestational age of less than 39 weeks, compared to the group in which it was performed at more than 39 weeks of gestation.
The key strength of the present study is that it used a large hospital-based retrospective cohort database. Furthermore, we performed a detailed examination of each woman’s medical record so that the indication for C-section could be clearly ascertained. The hospital routine requiring a consent form for antepartum elective or non-indicated C-section enabled us to determine truly non-medically indicated prelabour C-section. We sought to eliminate adverse outcomes overestimation (confounder: indicated C-section) by analyzing cases of antepartum C-section without clinical indication. The gestational age was assessed in all cases by the first-trimester ultrasound, routinely used to confirm gestational week. However, there are some limitations in our study: some findings might fail to reach significance because the sample size was relatively small for some comparisons between groups (type II error). Additionally, a reflection of type I error may exist in one or more significant findings. Second, the current sample is rather homogeneous, and future research should examine these outcomes in more heterogeneous populations in terms of their sociodemographic characteristics. Third, intrapartum stillbirth and neonatal deaths were not included in these analyses.
The extent to which the increase in the number of C-sections could be attributed to medical preference or maternal demand should be a focus of future debates. In this sense, our results contribute to the existing research on this subject and confirm that waiting until 39 weeks for elective C-section is advisable, similar to other findings around the world (36). It is important to highlight, however, that despite being an increasing trend due to maternal request, performing primary C-sections antepartum can lead to substantial public health implications due to its effects on neonatal outcomes (37-39).