Background and Aims Prior studies evaluating C-reactive protein (CRP) concentrations after major abdominal surgery suggested surgical trauma as major determinant of postoperative CRP levels, positively associated with higher pain scores, not considering time-of-day effects. Limited, controversial data exist regarding diurnal and seasonal pattern in serum hs-CRP, with higher levels in the morning and in the winter months in healthy subjects. No data exist regarding circadian effect on postoperative CRP values. In the present study which was approved by our hospital scientific/ethics committee,(ref. number: 35/6th/24–5-2017), we asked whether if any substantial diurnal variation of CRP levels occurs after caesarian section, according to time point of anaesthesia’s induction.

Methods A total of 90 parturient patients, ASA I-II, presented for urgent and/or elective caesarean section under spinal anaesthesia were assigned in three equal groups of 8 hours duration, A (morning/afternoon group), B (evening group) and C (night group), according to anaesthesia start time. Venous blood samples were collected on admission to the obstetric clinic, prior to spinal anaesthesia, at 2h, 4h,24h and 48h after surgery.

Results The mean CRP concentrations increased in all groups at 24 and 48h after surgery.Post-hoc analysis revealed significant differences in CRP levels in group B compared to group A at 24h (p<0,05) and 48h (p<0,05) and in group B compared to group C at 48h (p<0,05).

Conclusions Our finding of higher postoperative CRP levels at 24 and 48h in patients undergoing caesarian delivery in the evening, might be helpful to predict the possibility of severe pain and performe a more carefull pain control regimen.