Mar 14, 2007

Critiques of the Term Breech Trial (TBT)

Marek Glazerman published a scathing critique of the TBT in ACOG 's flagship journal, American Journal of Obstetrics & Gynecology . Here is the Pubmed Abstract. The argument notes:
  • Most cases (8 out of 13 in the vaginal delivery group) of perinatal mortality were unrelated to the mode of delivery.
  • Nearly half of all perinatal deaths arose from infants who should not even have been in the study---ie. undiagnosed twins, anenchephaly, & stillbirths.
  • There were far more fetuses with birthweights over 4000 gms in the group intended for vaginal delivery than in the planned cesarean group. Again, all of these fetuses should have been excluded from the study.
  • The standard of care at two thirds of participating hospitals was so low as to put vaginal deliveries at a definite disadvantage---no facilities for immediate resuscitation, bag/mask, or immediate intubation of newborns.
  • Roughly one third of all infants with significant morbidity failed to have an experienced obstetrician in attendance.
  • In a two- year followup, study authors themselves found no differences in neurological or developmental outcomes between planned cesarean and planned vaginal deliveries. In fact, infants from the cesarean group had slightly worse outcomes than those from the vaginal delivery group.
  • This last point effectively negates the trial's major findings. Rather audaciously, Glazerman suggests that the Trial Recommendations be withdrawn. Yet even if this were to happen, he thinks it is too late to rescue the rapidly dwindling option of vaginal breech delivery. Indeed, the Trial has has been overwhelmingly adopted in most of the developed and developing world.
MJ Turner discusses the further flaws of the TBT in the Journal of Obstetrics and Gynaecology (Aug 2006):
  • The findings may apply largely to primigravidas or women giving birth the first time. There were twice as many perinatal deaths among primigravidas as among multigravidas.
  • The slight differences in immediate perinatal outcomes were not related to delivery, but to labor, especially augmented or induced labor. The adverse effects of synthetic oxytocin and other uterine stimulants on breech deliveries is well known, but was not adressed in the study's conclusions. Even more disconcertingly, the study abandoned a pre-trial consensus to use oxytocin sparingly, if at all.
  • Turner concludes that the trial's findings should be reconsidered, although he,too, agrees it is probably too late.
In an early critique published in Birth (March 2002), Marc Keirse claimed hat study guidelines doomed vaginal delivery from the start. Why so?
  • A large majority (87%) of births without an obstetrician were in the planned vaginal group.
  • The study included 2 stillbirths, two cases of twins, and two with lethal malformations---many of which died, but none of whom should have been included in the trial.
  • One third of the babies who died were low birthweight babies---whose death may have had litttle to do with mode of delivery.
  • Finally, those countries with higher rate of successful vaginal deliveries had lower rates of overall morbidity and mortality. This implies that a familiarity with vaginal deliveries may be crucial for the ultimate outcomes of those deliveries. As intuitive but often overlooked point that is the focus of Kotaska's brilliant critique.
Andrew Kotaska expresses deep reservations about the TBT and randomized control trials more generally in the British Medical Journal (2004; vol 329):
  • The study achieved a remarkable 57% successful vaginal delivery rate only by asking those centers with lower vaginal birth rates to withdraw from the trial or increase their rate.
  • As a result, centers may have increased vaginal delivery far beyond their ordinary comfort or skill level, thereby reducing the success of vaginal delivery outcomes.
  • More disturbingly, they unwittingly compromised the safety of infants and mothers in the trial.
  • The delivery as well as selection of breech babies for a safe vaginal delivery requires considerable skill and finesse---not randomization, which may take the choice out of the physicians hands.
  • The questionable results of one randomized trial are now dictating a new standard of care worldwide. This does little justice to the complex variables that influence the safety of a vaginal breech delivery.

No comments: