The Term Breech Trial
The term breech trial (TBT) (Hannah, et al. 2000) was designed to conclusively determine if vaginal or cesarean section was the best mode of delivery for breech presentation. Previous studies suffered from small sample size, lack of randomization, and unclear inclusion protocols and outcome measures. The term breech trial was a randomized multi-center trial that included 2083 women from 121 centers in 26 countries. Inclusion criteria were singleton live fetus in frank or complete presentation at term (>=37 weeks). Exclusion criteria included fetopelvic disproportion, fetal macrosomia (or estimated weight >= 4000 grams), hyperextension of fetal head (undefined), clinician determined fetal anomaly or other mechanical condition, or a condition contraindicating vaginal delivery (e.g. placenta previa).
Planned cesarean sections were scheduled for 38 weeks gestation or more. Approved intervention included induction of labor, amniotomy or augmentation of labor for standard obstetrical indications, fetal heart monitoring intermittently or continuously, cervical dilation at least 0.5 cm/hour after the onset of active labor, descent of breech to the pelvic floor within two hours of full dilatation during second stage of labor, and delivery within one hour of active pushing. If there were fetal heart rate abnormalities or lack of progress, a cesarean was performed. If the baby were birthed vaginally, the baby was allowed to birth spontaneously up to the umbilicus, then controlled delivery of the after-coming head either with forceps or Mauriceau-Smellie-Veit maneuver occurred. Total breech extraction was not permitted.
The primary outcome was perinatal or neonatal mortality before 28 days or neonatal morbidity (birth trauma, seizures, Apgar score <4 at five minutes; cord-blood base deficit at least 15, hypotonia two hours, stupor, decreased response to pain, coma, intubation and ventilation, tube feeding, and admission to neonatal intensive care unit). The secondary outcome was maternal mortality or morbidity during six weeks post-partum. The study found planned cesarean section produced lower infant mortality and morbidity for babies in industrialized countries. There was no difference in maternal mortality or morbidity between vaginal and cesarean groups.
While this study is accepted as the gold standard in breech delivery outcome research, it is limited in several ways: 1) Inherent biases of the study design, 2) Recruitment of participants, 3) Categorical data analysis, 4) Use of non-parametric tests, 5) Presentation of initial findings, and 6) Presentation of follow-up findings.
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