• Diarmaid D Houlihan, Michael C Dennedy, Nandini Ravikumar, and John J Morrison.
• Department of Obstetrics and Gynecology, Clinical Sciences Institute, National University of Ireland Galway, University College Hospital, Galway, Ireland. john.morrison@nuigalway.ie
• J Perinat Med. 2004 Jan 1; 32 (4): 315-9.

ObjectiveTo investigate and compare the direct effects of compounds used in the treatment of hypertensive disease in pregnancy on human umbilical artery resistance in vitro.MethodsIsometric tension recordings were performed under physiological conditions on human umbilical arterial rings (n=30). The in vitro effects of labetolol, hydralazine, alpha-methyldopa, nifedepine and magnesium sulphate (at concentration ranges from 1 nanomolar to 1 millimolar), and their respective vehicle controls, were measured. Results were expressed as -logEC50 (pD2) and mean maximal inhibition values for each compound.ResultsAll compounds investigated, except alpha methyldopa, exerted a significant relaxant effect on umbilical arterial tone. Alpha-methyldopa was significantly less potent when compared to all other compounds (mean maximal inhibition value [20.89+/-7.99%] versus all other agents [range 63.15+/-8.70-84.12+/-3.84%] (P<0.01)). The dose response curve of nifedipine yielded a significantly greater PD2 value when compared to that of hydralazine, labetalol, and magnesium sulphate (PD2 value [5.82+/-0.34] versus the above groups [range 3.10+/-0.09-3.52+/-0.14] (P <0.01)).ConclusionThese findings demonstrate that agents commonly used for the treatment of hypertensive disease in pregnancy, excluding alpha-methyldopa, have significant direct effects on the feto-placental circulation. These results suggest that alpha-methyldopa administration during pregnancy is less likely to produce significant direct effects on fetal vasculature then other agents used.

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