Effects of routinely given pethidine during labour on infants' developing breastfeeding behaviour. Effects of dose-delivery time interval and various concentrations of pethidine/norpethidine in cord plasma.

A standard dose of 100 mg of pethidine was given im to 13 healthy primiparae during labour. The aim of the study was to investigate whether developing breastfeeding behaviour in the newborn infant was associated with the dose-delivery time interval (DDI) or with the plasma concentration of pethidine and norpethidine in mixed cord blood at birth. The DDI was found to be unevenly distributed with no pethidine exposures in the time interval 5.4-8 h. The material was therefore divided into a "short DDI" group (1.1-5.3 h) and a "long DDI" group (8.1-9.9 h). The infants in the "short DDI" group had a depressed sucking behaviour in 15-45 min of observation and a delayed initiation of lip and mouth movements when compared with the infants in the "long DDI" group. Six of the thirteen infants did not suck their mothers' breasts during the observation period. These infants had higher median plasma concentrations of pethidine at birth than the seven infants who did start sucking. No differences wer found between the plasma levels of norpethidine and the behaviour. It was concluded that 100 mg of pethidine im as an analgesic given under routine conditions may have unfavourable effects on infants' developing breastfeeding behaviour if the DDI is short.