In-vivo measurement of intrauterine gases and acid-base values early in human pregnancy

A new multiparameter sensor that combines electrochemical and fibre-optic t echnology was used for continuous in-vivo investigation of pH, carbon dioxi de partial pressure (PCO2), oxygen partial pressure (PO2), bicarbonate conc entration (HCO3-), base excess, and oxygen saturation (O(2)Sat) early in hu man pregnancy. The sensor was inserted into the amniotic cavity and the pla cental bed of 16 pregnancies at 10-15 weeks gestation, before termination u nder general anaesthesia, Amniotic fluid and retroplacental blood from the same site were also aspirated and analysed by means of cartridges and a por table blood gas analyser. Eleven series of measurements were obtained. The variation in measurements over the 5 min of monitoring was less than or equ al to 10% for all parameters. The sensor was damaged during insertion into the amniotic cavity in one case and in the placental bed in four cases. Mea surements of PO2 in both the amniotic cavity and the placental bed and of p H in the placental bed were higher using the cartridges than in vivo. The r esults indicated that in-vivo monitoring of fetoplacental gas and acid-base with a sensor is stable and accurate. Such technology will be helpful in i mproving our understanding of the fetoplacental metabolism in normal and co mplicated pregnancies.