In normotensive women, low-dose OC may increase blood pressure to an extent that, at least in some women, may affect blood pressure control towards 'hypertensive values'. This stresses the importance of monitoring blood pressure values during OC treatment.

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Objective To evaluate factors contributing to both placental hypoperfusion and maternal Design Single centre, comparative study of calcium-channel density and affinity in the placental bed Setting Teaching hospital.Participants Twenty-two primigravidae in the third trimester of pregnancy: 10 with pre-eclampsia and 12 normotensive.Methods Plasma levels of endothelin-1 (by RIA) and noradrenaline (by HPLC-ED) were measured. Both pharmacological characterisation and anatomical localisation of dihydropyridinesensitive binding sites (using radioligand-binding studies and autorradiographic techniques) were determined with 3H-isradipine in placental bed tissues to determine both the density (Bmax) and the affinity (Kd) of receptor sites. Results Higher plasma levels of endothelin-1 and noradrenalin were found in women with preeclampsia compared with normotensive women. Placental bed tissues bound 3H-isradipine in a saturable, reversible time and temperature-dependent manner with very low Kd values. Study of the 3H-isradipine specificity binding included the use of several dihydropyridine displacers. In the group with pre-eclampsia the Scatchard analysis of the results showed a significant increase ( P < . Autoradiography confirmed that in the placental bed tissue of those with pre-eclampsia there was a much higher silver grain density in the arteries walls, compared with norrnotensive women.0 ConclusionsIn pre-eclampsia there is an increase in the maternal circulation of two strong vasoconstrictor factors (endothelin-1 and noradrenalin) and a sharp increase both in the density and the affinity of calcium-channel binding sites in placental bed central area. The latter may strongly contribute to the perpetuation of the uteroplacental hypoperfusion either by itself or by amplifying the local actions of circulating factors, such as endothelin-1 and noradrenalin.vasoconstriction in pre-eclampsia.of pregnant women with normotension and pre-eclampsia.

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