RAMB Maio/Junho 2015

irth

route

case

cesarean

section

pregnancy

ssoc

ras

2015; 61(3):196-202

201

patients compared to trial of labor in terms of effective-

ness and safety.

The study by Landon et al. illustrates the difficulties

presented above because, despite being the most impor-

tant prospective observational longitudinal study con-

ducted to evaluate this outcome, it has biases inherent to

the study design, which are easily identified and compro-

mise the analysis (

)

In this study, despite the fact that

the women included in both groups were mostly obese,

with BMI > 30 Kg/m

, there was heterogeneity especially

regarding maternal age, ethnicity, smoking status, obstet-

ric history, factors leading to indication of the first cesar-

ean delivery, obstetric diseases, gestational age, and fetal

weight at birth. The study was multicentric, and thus tri-

al of labor rates varied greatly among different centers

included (ranging from 18 to 63%), with a decrease

throughout the study period (in 1999, there were on av-

erage 48% of patients undergoing trial of labor, falling to

30%, in 2002). Despite that, we have identified a signifi-

cant increase in the number of maternal complications

in cases of pregnant women undergoing trial of labor

(such as need for blood transfusion, diagnosis of endo-

metriosis, and uterine rupture), compared to patients re-

ferred for elective cesarean section, especially in cases

where there was failure to progress. However, due to the

heterogeneity of the groups and the exclusion of patients

who underwent elective cesarean section at the beginning

of labor, the interpretation of these results has limited

range (

)

In 2012, another concurrent observational longitudi-

nal study, aimed at analyzing the outcomes related to type

of delivery on maternal morbidity and mortality (here con-

sidered as a secondary outcome), was published

(

)

Also

multicentric, this study was less questioned in terms of

methodology compared to the first trial shown above, since

the groups were homogeneous regarding intention to treat

(excluding body mass index, socioeconomic status and ob-

stetric indication of first cesarean section). There was no

significant difference between the groups; however, it should

be noted that the outcome of interest (maternal morbidi-

ty and mortality expressed by the occurrence of at least one

serious complication such as death, uterine rupture, post-

operative complications, bleeding, thromboembolism and

infection) was characterized as secondary (

)

Also in 2012, a study (secondary analysis of the co-

hort study by Landon et al.,

published in 2004) that ad-

opted a multiple logistic regression model was published.

Using a propensity score with control of presented con-

founding factors (heterogeneity between groups), the

study had the main objective of comparing the progno-

sis by type of delivery in cases with previous cesarean sec-

tion. Even after this analysis, consistent with findings re-

ported in the initial study, it was found that elective

cesarean indication was associated, to the detriment of

trial of labor, to a significant reduction of maternal com-

plications (

inal

recommendations

Based on the evidence available at present, trial of labor

(TOL) is a reasonable option for women with a previous

cesarean section (performed through transverse uterine

section).

The available data derived from observational longi-

tudinal studies (concurrent or not) show that both labor

and elective cesarean section in pregnant women (with a

single fetus in cephalic presentation) with one previous

cesarean section are associated with significant risks and

benefits, which differ for the mother and the fetus (risk

of uterine rupture, febrile morbidity, need for blood trans-

fusion and hysterectomy).

Characteristics that are clearly associated with a fa-

vorable progress of trial of labor are: indication of the

first cesarean section (non-recurring reason) and a histo-

ry of vaginal delivery, in the case of multiparous women

with a previous cesarean section.

Since data is not conclusive as to the best type of de-

livery in this context, recognition of the prognostic fac-

tors associated with the failure of the trial of labor should

be helpful, as an attempt to select more properly women

who should effectively undergo such procedure.

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