Major Finding: The likelihood of delivery within 12 hours was significantly increased from 14% with 30-mL Foley catheter inflation to 26% with 60-mL inflation.
Data Source: The prospective LIFT study of 192 women.
Disclosures: Dr. Delaney reported no study sponsorship or conflicts of interest. Coauthor Dr. Aaron Caughey was funded as a Robert Wood Johnson Physician Faculty Scholar.
CHICAGO — Inflating a transcervical Foley balloon catheter to 60 mL is more effective at inducing labor than standard inflation to 30 mL, based on data from the prospective LIFT study.
The likelihood of delivery within 12 hours was significantly increased from 14% with 30-mL inflation to 26% with 60-mL inflation. The number needed to treat for this outcome is nine, Dr. Shani Delaney and associates reported at the annual meeting of the Society for Maternal-Fetal Medicine.
“The number needed to treat of nine women provides an achievable intervention without increasing cesarean delivery rates and [while still] maintaining both maternal and neonatal safety,” she said.
The Labor Induction With a Foley Balloon Trial (LIFT) failed to meet its primary end point of delivery within 24 hours, with 64% of controls and 66% of the 60-mL group achieving this outcome. The percentage of women giving birth within 24 hours was higher than anticipated in both the control and study groups; thus there was not enough statistical power to detect such a small difference between the groups, Dr. Delaney explained in an interview.
As expected, larger balloon inflation to 60 mL produced significantly increased cervical dilation after expulsion compared with 30-mL inflation (4 cm vs. 3 cm).
An 18 French Foley catheter with a 30-mL balloon tip was inflated to 30 mL in 94 evaluable patients and to 60 mL in 98 patients. Intravenous oxytocin was started within 30 minutes of balloon placement.
Only age was significantly higher at 31.4 years in the control group vs. 29.4 years in the 60-mL group.
The study design was influenced by previous trials, which have reported inflation rates of 30–80 mL, Dr. Delaney said.
The American College of Obstetricians and Gynecologists issued a new practice bulletin for labor induction in August 2009 stating that the “Foley catheter is a reasonable and effective alternative for cervical ripening and inducing labor,” but ACOG did not specify inflation sizes.
During the discussion of the study, a member of the audience sounded a word of caution regarding the findings, noting that most manufacturers recommend inflation to only 50 mL.
There was no difference in maternal or neonatal morbidities between treatment groups, said Dr. Delaney of the department of obstetrics and gynecology at the University of Washington in Seattle.
“If only a 30-mL balloon tip is available, inflation to a volume of 60 mL appears to be safe,” she said.
Maternal outcomes that were similar in the control and 60-mL groups included maximum oxytocin dose (19.1 vs. 19.2 mU/min), median delivery time (20 hours vs. 18.8 hours), spontaneous vaginal delivery (66% vs. 63%), cesarean delivery (21% vs. 23%), chorioamnionitis (15% vs. 19%), meconium (21% vs. 20%), cervical laceration (2% vs. 1%), and placental abruption (1% vs. 2%).
Among infants, 5-minute Apgar scores less than 7 were reported in 5% of the 30-mL group and 4% of the 60-mL group. Umbilical artery blood pH was identical in both groups at 7.27, while umbilical artery base excess was −3.38 in the 30-mL group and −2.95 in the 60-mL group.
In a multivariate analysis, delivery within 12 hours was significantly increased with 60-mL balloon inflation among all patients (relative risk, 1.84), and particularly among nulliparous women (RR, 2.88), Dr. Delaney reported.