Evidence that natural benzodiazepine-like compounds increase during spontaneous labour

Natural benzodiazepine-like compounds (NBDZ) are present in the blood of normal people free of commercial benzodiazepine medication. In this work, we evaluated the levels of NBDZ in maternal/foetal serum during delivery after spontaneous labour (VD) or caesarean section (CS). For both the VD (n=11) and the CS (n=11) groups (VD+CS=22), three blood samples were collected at three different times: the first was collected three days before labour, the second immediately after delivery or at fetal abdominal extraction and the third one was obtained at second day post-partum. NBDZ were measured by radioreceptor binding assay after HPLC extraction and purification while cortisol was measured through radioimmunoassay. In the VD group, a significant increase of NBDZ levels occurred at labour in comparison with the levels found in pre- and post-partum periods. By the contrary, no differences in NBDZ levels were found in the CS group at the three different times. The levels of cortisol in the VD group were found to be higher at labour than that determined at pre- and post-partum. Again no significant changes were found in the CS group. These findings suggest for the first time that labour is associated with a marked increase of NBDZ which could be envisaged as a stress-related event.