A study of the relationship between circulating beta-endorphin-like immunoreactivity and post partum 'blues'.

Plasma beta-endorphin-like immunoreactivity was studied in 43 pregnant women at 36 weeks gestation and in 23 of these at delivery and 24 h post-partum; an attempt made to correlate changes with various social, psychological and obstetric factors, including the 'post-natal blues'. Beta-endorphin levels were elevated at 36 weeks gestation and term, increased to very high levels during labour and fell rapidly within 1 h of delivery. A negative correlation was observed between the woman's estimate of her pain in labour and the beta-endorphin levels post-partum, suggesting an analgesic role for beta-endorphin in labour. A positive correlation was also observed between the levels of beta-endorphin at delivery and the woman's attitude to her pregnancy at 36 weeks and a negative correlation between the 'post-natal blues score' and the beta-endorphin level at 36 weeks. However, the 'blues' did not correlate either with the beta-endorphin level at delivery or 24 h post-partum nor with its rate of fall in the first 24 h. Our general finding that there was no consistent social, psychological or obstetric factor which predisposes women to develop 'post-natal blues' still supports the hypothesis that humoral factors, of which beta-endorphin may be one, rather than psychological factors are important in the genesis of this syndrome.