Observational Study: Timing of elective c-section

This is the first pregnancy for this woman, I think her physician should tell her every things about advantages and disadvantages on vaginal delivery and cesarean delivery. If this time she chooses cesarean section, it will affact her next pregnancy and delivery and etc. However, if she insists to have a elective cesarean section, the physician should suggest her to wait at least another week to let her baby stay until to 39 weeks because her baby will have less neonatal respiraoty morbidity if her baby was delivered after 38 weeks according the results of this study.

It is not good for her to have an elective c-section at 38weeks gestation, because there is increased risk for her baby suffered RDSin this gestation week; if she can wait until 39+0 wk to have an elective c-section, RDS risk will be decreased.
As a doctor, you should also tell her all the complications about elective c-section if she decides to choose it.

I agree with both of the responses that were provided for this question. Both responses suggest that the woman needs to be informed of the risks (and benefits) of elective cesarean section, especially at 38 weeks’ gestation, and that she should be encouraged to wait until 39 weeks gestation (assuming there are no medical indications for earlier delivery).

The issue of planned elective cesarean delivery is the subject of much debate in North America. There is obviously no right or wrong answer to this question, and opinions range across the entire spectrum. Two articles from the March 2, 2004 issue of the CMAJ offer commentary on this subject. In one (attached as a PDF), Dr. Hannah concludes with this statement: “However, if a woman with-out an accepted medical indication requests delivery by elective cesarean section and, after a thorough discussion about the risks and benefits, continues to perceive that the benefits to her and her child of a planned elective cesarean outweigh the risks, then most likely the overall health and welfare of the woman will be promoted by supporting her request”.1 Another viewpoint is offered in an accompanying commentary.2 In this commentary, it is noted that The International Federation of Gynecology and Obstetrics guidelines state: “Because hard evidence of net benefit does not exist, performing cesarean sections for non-medical reasons is ethically not justified”.2

1. Hannah ME. Planned elective cesarean section: A reasonable choice for some women? CMAJ 2004; 175(5):813-4.
2. Singer B. Elective cesarean sections gaining acceptance. CMAJ 2004; 170(5): 775.

This was a retrospective cohort study.

Retrospective, observational study.

As mentioned by the respondents, this is a retrospective cohort study.

Vaginal delivery group was being compared in this study and the primary outcomes in this study were neonatal respiratory mobidity, respiratory distress syndrome (RDS), and transient tachypnea of the newborn (TTN).

1, compared groups in this study:
a, infant group delivered by caesarean delivery(including elective caesarean
delivery and emergency caesarean delivery);
b, infant group delivered by elective caesarean delivery;
c, infant group delivered by vaginal delivery (matched for week of gestation);

2, primary outcomes:
a, Neonatal respiratory morbidity risk (including RDS and TTN), was
significantly higher in the infant group delivered by elective caesarean
delivery compared with vaginal delivery;
b, while TTN risk in caesarean delivery was not increased, the RDS risk is
greaterly increased;
c, RDS risk is greatly increased in weeks 37+0 to 38+6; after 39+0 wk, there
was no significant difference in RDS risk.

(TTT: transient tachypnea of the newborn; RDS: respiratory distress syndrome)

The two groups being compared in this study are: infants of women who had an elective section, without labour, at term and infants of women who had vaginal delivery at term. Infants of women in labour prior to cesarean section were excluded from the study.

As both respondents mentioned, the primary outcomes being examined are respiratory morbidity, including transient tachypnea of the newborn (TTN) and respiratory distress syndrome (RDS).

Inclusion criteria: Women had elective cesarean delivery in the absence of labour under conventional spinal anaesthesia with 2 ml of 0.5% bupivacaine in the form of bolus doses.

Exclusion criteria: Patients in labour prior to cesarean section were excluded.

I agree with the author’s choice of these inclusion/exclusions.

Newborns with major malformations were also excluded. I agree with it.

The inclusion criteria were:
1. Neonates admitted to the University of Padua nursery from January, 1998 to December, 2000.
2. Women whose pregnancy was at term (37+0 to 41+6) as estimated by last menstrual period
3. Low-risk pregnancy (ie, uncomplicated by conditions identified prenatally that were capable of increasing risk to the neonate)

The exclusion criteria were:
1. Women in labour prior to cesarean section.
2. Women (in the elective section group) who had anaesthesia other than conventional anaethesia with 2ml of 0.5% bupivacaine in the form of bolus doses.
3. Women in the vaginal delivery group with twin fetuses or a fetus in the breech presentation.

These seem reasonable, with one exception. As a general rule, we want the comparison group (vaginal delivery group in this study), to be similar, in all respects, to the elective section group. In this way, differences in outcome can be attributed to the factor of interest (in this case, elective section). The authors state that “vaginally delivered women with conditions potentially affecting the likelihood of an adverse neonatal outcome (breech presentation or twinning) were also excluded form the low-risk population”. This exclusion to the vaginal delivery group means that the two groups are not necessarily comparable (e.g., as shown in the second paragraph of the result’s section, 8% of the elective c-section group were twins and 27% were a breech presentation). If twinning or breech presentation adversely affects the likelihood of the respiratory outcome, independent of mode of delivery, than the results could be confounded by these factors. In this situation, the relative risk for respiratory morbidity among the elective cesarean section group would be biased away from the null value (ie, the relative risk would be larger). Therefore, I do not think twins or breech presentations should have been excluded from the group with vaginal deliveries.

There were only two maternal characteristics in table 1. The authors did not compared these characterstcis using statistical method. For percentage of nulliparae, significant difference between these tow groups could be found using chisqure test.

This paper does not give us a table that compares baseline characteristics in the two groups. As mentioned by the respondent, there are two maternal characteristics compared in Table 1: age and proportion nulliparae. The groups do not appear to be comparable on parity, so this factor may be confounding the results (the analyses did not adjust for any factors). As well, there may be other factors that are potential confounders, but the authors have not provided the data to determine this.

I agree with you. The OR (95%CI) should be 4.64 (2.28--15.38) according to my calculation.

My interpretation of the findings for RDS among infants born between 37+0 to 38+6 weeks is that women whose newborns were delivered by elective cesarean delivery between 37 and 38 weeks’ gestation had close to a 13-fold increase in the risk of RDS compared to newborns delivered vaginally between 37 and 38 weeks. This odds ratio was statistically significant, although the width of the confidence interval (3.57-35.53) indicates a low level of precision of the odds ratio.
For RDS among infants born between 39-41 weeks gestation, there was a 15% increase in the risk of RDS among newborns delivery by elective cesarean delivery compared to vaginal delivery, although this increase was not statistically significant.

I totally agree with you that the analysis should be conducted only for those who had an elective caesarean delivery and to compare respiratory morbidity among delivery at the different gestational weeks as the title suggests. The odds ratio for RDS among women who had an elective section at 37-38 weeks compared to those who had an elective section at 39-41 weeks was 5.07 (1.77--14.52).

There are two different questions that can be asked, both of which are interesting.
From the title of this paper, it seems that the question of interest is: Does timing of elective cesarean section (at term) have an effect on neonatal respiratory morbidity? To answer this question, it seems that the analysis should be conducted only for those women who had an elective cesarean section and to compare respiratory morbidity at the different gestational weeks. The odds ratio for RDS among women who had an elective section at 37-38 weeks compared to those who had an elective section at 39-41 weeks can be computed from the numbers given in the table and the first paragraph of the results section. The numbers that are in the 2x2 table are:

Elective section 37-38 weeks:
RDS Yes: N=25
RDS No: N=740

Elective section 39-41 weeks:
RDS Yes: N= 4
RDS No: N=515

OR=4.35, 95%CI= 1.4, 14.8

The other question that could be asked is: Does mode of delivery influence the risk of respiratory morbidity among infants born between 37 and 41 weeks’ gestation? This is also an interesting question, and their Figure suggests that at 37 and 38 weeks’ gestation, elective section without labour is a risk factor for RDS, whereas vaginal delivery between 37 and 38 weeks’ gestation is not a risk factor for RDS.

The results did not surprise me because the lung of babies with lower gestational age did not mature yet when they were delivered.

Tiny air sacs called alveoli are located at the tips of the body’s smallest breathing tubes, called the bronchi. The alveoli are responsible for passing oxygen into the blood. In the last stages of pregnancy, from 34 to 37 weeks, the cells in the alveoli normally produce a substance called surfactant.
Surfacant reduces the surface tension of fluids that coat the lungs so the air sacs can expand at birth and the infant can breathe normally.
When an infant is born prematurely (baby delivered with elective section and lower gestational age), the cells in the alveoli do not yet have enough surfacant formed and the alveoli cannot expand.
Very premature babies may have lungs that are so stiff they cannot breathe on their own. Or, the baby may be able to start breathing, but the “airless” lungs collapse and cause respiratory distress.

I asked Dr. Alec Allen, a neonatologist at Dalhousie University and the IWK Health Centre to comment on this question. He gave this response:

The air sacs are expanded in the fetus prior to birth with lung fluid (no surface tension). With the introduction of gas into the alveolus at birth, surfactant stabilizes and reduces the surface tension. Surfactant has two actions: it lowers tension and stabilizes the alveoli so that surface tension remains constant in alveoli of different sizes. Without surfactant, the smaller alveoli empty into larger alveoli and the lung collapses. The physiologic consequence of surfactant deficiency is respiratory distress. As one of the respondents mentioned, surfactant is normally produced from 34 to 37 weeks’ gestation and beyond. Figure 1 from the article suggests that it is the combination of elective section in the absence of labour and delivery at 37-38 weeks that increases the risk of RDS, since vaginal delivery at 37-38 weeks was not associated with an increased risk of RDS.