Summary. A simple and reliable method for the estimation of cytidine deaminase (cytidine aminohydrolase; EC 3.5.4.5) activity in pregnancy serum is described. This enzyme does not require magnesium for activation and is also more stable than deoxycytidylate deaminase (dCMP deaminase, dCMP aminohydrolase; EC 3.5.4.12). There was excellent correlation between the two enzymes (r= 0.92). Both enzymes showed increased activity in abnormal pregnancy. Both enzyme activities were found to be similar in 1305 maternal serum samples and therefore due to the simplicity of cytidine deaminase estimation it is recommended for the screening of large numbers of antenatal sera for abnormal pregnancies.

The value of measuring plasma urate and serum deoxycytidylate deaminase (dCMP deaminase) for the early diagnosis of pre-eclampsia has been investigated in 45 patients. A combination of increased blood pressure and increased plasma urate identified 19 patients with a high incidence of fetal and maternal morbidity ascribable to pre-eclampsia. Seventeen of the 19 patients also had an increased serum dCMP deaminase. Serial antenatal observations for a mean period of 104 days (36-179 days) on 33 of the patients demonstrated that plasma urate and serum dCMP deaminase increased together as early changes in the development of pre-eclampsia. In six patients, blood pressure, plasma urate and serum dCMP deaminase all increased but in only one was the rise in blood pressure the first change. Elevations of plasma urate and serum dCMP deaminase are therefore both early features of pre-eclampsia. Serial measurements can give warning of the disorder before the appearance of other clinical features. The change in dCMP deaminase is probably another reflection of early renal involvement in the pre-eclamptic process.INCREASED plasma urate concentration is an associated with a high perinatal mortality early and characteristic feature of pre-eclampsia particularly between 28 and 36 weeks gestation which helps to differentiate the disorder from (Redman ef al, 1976b). It is therefore possible essential and cther chronic forms of hyper-to use serial measurements of blood pressure texion coinciding with pregnancy (Pollack and and plasma urate to diagnose the development Nettles, 1960;McFarlane, 1963). On average, of pre-eclampsia. The time at which the plasma the plasma urate begins to rise six wee!

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