Supplementary Material for: The impact of maternal body mass index on fetoscopic laser surgery for TTTS

Background
Both a low and an increased body mass index (BMI) are risk factors for surgical complications. It is less clear whether they also affect the outcomes of fetoscopic procedures. In this manuscript we aimed to assess the effect of maternal BMI on operative and pregnancy outcomes following fetoscopic laser ablation of placental anastomoses for twin-twin transfusion syndrome (TTTS).
Methods
We retrospectively reviewed all patients with twin pregnancies complicated by TTTS treated with fetoscopic laser surgery at the Ontario Fetal Centre, Toronto over a 24 year period. Demographic and procedural data as well as pregnancy and delivery outcomes were prospectively collected as part of our quality control program. Patients were divided into 6 groups for BMI at the time of surgery: BMI <20, 20-24.9, 25-29.9, 30-34.9, 35-39.9 and ≥40kg/m2. Collected variables included demographics, operative characteristics, operative complications, obstetric complications, TAPS, TTTS recurrence, intrauterine (fetal) death (IUFD), gestational age (GA) at delivery and survival. Outcomes of all groups were compared to the ‘normal weight’ reference cohort (BMI 20-24.9kg/m2).
Results
Of 1,012 patients in our database, 859 were twin pregnancies treated with laser for TTTS. Pregnancy outcomes were available for 515. Of all patients, 40% were categorized as normal weight, 8% were underweight, 24% were obese and 4% had a BMI > 40kg/m2. Patients with a higher BMI had higher parity (p=0.0001), longer cervical length (p=0.008) and a significantly higher TTTS stage (p=0.0003) at the time of surgery. There were no significant differences between groups in terms of surgical or anaesthetic characteristics or perinatal complications. Patients with a higher BMI however, had a lower number of anastomoses ablated at the time of surgery (p=0.047).
Conclusion
BMI does not significantly affect operative or perinatal outcomes in patients undergoing fetoscopic laser ablation for severe TTTS, despite being at a higher stage at diagnosis.