Uterine dystocia, often of unknown cause, remains one of the commonest
causes of emergency caesarean section. We have tested the hypothesis
that small acidic changes in pH, that can occur during labour contract
ions, can decrease contractions and contribute to dystocia. We simulta
neously recorded intracellular pH (pH(i)) and force in human myometriu
m: acidification abolished contractions. Such effects of pH(i) on uter
ine contractile acitivity may be of clinical significance. Blood flow
reduces during each uterine contraction; the resulting fall in pH(i) c
ould lead to inefficient uterine action in some labours and failure to
progress (ie, dystocia).