From the World Federation of Societies of Anesthesiologists' Update in Anesthesia Volume 31 (2016) (My pace of reading's too slow):
“Overall, warming significantly reduced maximum temperature change compared with control (standard mean difference –1.27°C; confidence interval –1.86°C to –0.69°C; P = 0.00002). The subgroup analysis revealed no significant difference between the types of warming method used (forced air warming or fluid warming). Of the secondary outcomes, patient warming resulted in a significant reduction in shivering, a reduction in the incidence of hypothermia, improvement in thermal comfort and increase in umbilical artery pH.”
Last time in Melaka I was militant about keeping mothers warm during Caesarean sections; it was a failure if they shivered. I'd both force-air warm them and put fluid warmers. I'd rather they complain they complain that it's too warm (after the abdomen is open) that have them shiver. It's good that there is a rational to be more vigilant about the mothers' temperatures in the OR.