Changes in milk composition associated with pethidine-PCEA usage after Caesarean section

The effect of pethidine as patient-controlled epidural analgesia (PCEA) on specific biochemical components in breast milk in relation to the timing of secretory activation is not well investigated. The aim of this study was to compare biochemical timing of secretory activation between women who had a vaginal (V) or Caesarean birth with pethidine-PCEA (CBP). Several milk samples were collected daily from 36 mothers (17 V, 19 CBP) for the first 265h post-partum. Protein and lactose concentrations and Na+ and K+ ion levels were measured. Samples were assigned to three time periods: 0-72, >72-165 and >165-265h post-partum for statistical analyses. Data were analyzed using linear mixed effect models. In the first 72h post-partum, the mean difference in lactose concentration was 5gL(-1) higher in group V (P<0.05). From >72-165h post-partum, protein and Na+ concentrations were lower in group V (P=0.05, P=0.02), and K+ levels were higher in group V (P<0.001). From >165-265h post-partum, there were no significant differences between the groups. Biochemically, secretory activation had occurred by 72h post-partum in both groups. There were greater variations in measured biochemical components observed within group CBP initially. However, by 165h post-partum, there were no differences in the biochemical components between the groups. This suggests that effects of pethidine-PCEA are diminished by 72h post-partum and undetected by 165h.