Trial of scar

Comparison of transabdominal versus transvaginal ultrasound to measure thickness of the lower uterine segment at term

OBJECTIVE

To compare the accuracy of transvaginal (TVS) versus transabdominal (TAS) ultrasound to assess the thickness of the lower uterine segment (LUS).

METHODS

Eighty-three pregnant women admitted for an elective cesarean delivery were enrolled. LUS thickness was measured using both TVS and TAS prior to the cesarean. The actual thickness of the LUS was measured using a sterile metal ruler after the neonate had been delivered.

RESULTS

Seventeen women had unscarred uteri (20.1%); 41 had had one previous cesarean (49.4%); and 25 had had two previous cesareans (30.1%). Mean thickness of the LUS measured after delivery was 7.58+/-1.3 mm in unscarred uteri; 5.09+/-1.4 mm for one cesarean; and 3.92+/-1.1 mm for two cesareans (P<0.01). Actual thickness of the LUS showed a significant correlation with TVS among the total (r(s)=0.89); with unscarred uteri (r(s)=0.68); with 1 cesarean (r(s)=0.89); and 2 cesareans (r(s)=0.68), while with TAS the correlations were significant only with the total (r(s)=0.53) and 2 previous cesareans (r(s)=0.63) (P<0.01).

CONCLUSION

TVS is a more accurate method of assessing the thickness of the LUS compared with TAS.

Cardiotocography and medicolegal issues

Obstetric litigation is on the increase. A review of litigation cases reveals that the majority of claims relating to the intrapartum period arise because the cardiotocograph- (CTG) was misinterpreted or because inappropriate action was taken in the presence of fetal heart rate abnormalities. Compulsory education and training in the interpretation of CTGs and in best practice are key factors in minimizing the threat of litigation. Newer methods, such as pulse oximetry or fetal electrocardiogram waveform analysis, can act as adjuncts to CTG and help to avoid birth asphyxia and hence litigation.

Management of previous cesarean section

PURPOSE OF REVIEW

The management of cesarean sections causes much controversy among healthcare providers, patients, and insurers. A trial of vaginal birth after previous cesarean is reported to be a safe and practical method to reduce the rate of cesarean sections. The popularity of vaginal birth after previous cesarean has increased over the past two decades, but rates have recently started to decline again. This review will evaluate recent literature that might be responsible for this reversal in trend.

RECENT FINDINGS

Earlier studies on previous cesarean section pregnancies focused primarily on the success rate of vaginal birth after previous cesarean, which is reported to be 60-80%. Recent large, retrospective, population-based cohort studies examined the maternal and neonatal safety of trial of labour compared with elective repeat cesarean delivery, and confirmed that the risks of uterine rupture and neonatal mortality were significantly increased after trial of labour, particularly when induced with prostaglandins. However, the absolute risk of adverse events remains small. The maternal and neonatal morbidity risk increases when vaginal birth after previous cesarean attempts fails, which emphasizes the importance of careful case selection.

SUMMARY

Recent studies highlighted the risks of attempted vaginal birth after previous cesareans, especially when trials fail, but have not addressed the long-term risks of an elective repeat cesarean delivery. The assessment of treatment risks by observational studies is subject to bias, because the different treatment groups may not be comparable at the outset. In the absence of better data, the counselling of such women must currently be based on this evidence.

Vaginal birth after cesarean delivery

VBAC is considered safe and is often successful in carefully selected populations of women. Women with prior CDs are given the option of elective repeat CD or a trial of labor; neither option is risk free. Less morbidity is encountered in women with successful VBACs versus those with elective repeat CD. Patients who undergo successful trials of labor experience fewer blood transfusions, fewer postpartum infections, and shorter hospital stays and generally have no increased perinatal mortality. The high CD rate begins with the high frequency of the first CD. Therefore, a concerted effort should be made to decrease primary CDs. Paul and Miller remind us of the importance of the decision to proceed with the initial CD in their statement, "once a cesarean, always a scar (p 1907)." Many patients present for prenatal care with one or more prior uterine scars. Careful and thoughtful counseling of patients with a previous CD regarding the risks and benefits of a labor trial based on the current available literature is prudent. Pitkin's editorial in Obstetrics and Gynecology in 1991 stated, "Without question, the most remarkable change in obstetric practice over the last decade involves management of the woman with a prior cesarean delivery (p 939)." Controversies regarding the management of women with scarred uteri remain. In his review of the CD controversy, Flamm leaves us with an important thought: "A woman with a prior cesarean is at increased risk regardless of her mode of birth, and eliminating VBAC will not eliminate the risks. Vigilance with respect to primary cesarean delivery is the only way to avoid this dilemma (p 315)."