Everyone agrees that high blood pressure during pregnancy requires treatment regardless of underlying cause, the confusion is at what level should treatment be started. The Working group report was a bit confusing in stating treatment must be started when levels reach 100-110 mm Hg diastolic and 160-70 mm Hg systolic. Many, however, start treatment at lower levels, especially our Australian and European colleagues, and Obstetricians who consult with and are influenced by their medical colleagues.
The approach to when to treat is based on the following data. Systematic analyses have demonstrated no effect of treating mild or moderate hypertension on pregnancy outcome (or the development of superimposed preeclampsia in women with essential hypertension). The immediate safety and long term safety of these drugs on the fetus are yet to be established with certainty (For example even though many of these drugs have no known teratagenic effects we do not know if they will have effects on the development of the fetal autonomic nervous system etc., an area known as non-genetic influences on fetal development. Said simply, if you do not have to give a drug during pregnancy; do not!) Thus the only current reason to treat is when levels are sufficiently high to threaten the mother (stroke, bleeding, heart failure, etc.) Again some texts permit levels to 170/110 mm Hg, but many of us including this responder will treat once diastolic levels increase to or above 100 mm Hg in an essential hypertensive, or to or above 105 mm Hg in a preeclamptic. In addition I do not let systolic levels exceed 160 mm Hg. Finally, the magnitude of the rise as well as whether the patient has signs or symptoms is important, as well as whether patients have indication for treatment at lower levels such as underlying cardiovascular or renal compromise..
Having said the above, let me note that information on which these recommendations were made are poor and this is an area in need of substantially more research, primarily well designed trials to determine if mild to moderate hypertensive levels should be treated in pregnant women.
Systematic analyses of the literature have tried to determine the "best" drugs, but critically read only suggest we still need to perform these trials correctly. The drugs with the longest history of use in pregnancy without a plethora of bad reports seems to be what guides most of us, and the drugs most commonly used today are labetalol and alpha-methyl dopa for chronic hypertension and hydralazine and labetalol when the pressure rises suddenly and dangerous requiring hospitalizations and the giving of drugs by vein or injection. While many worry about the use of betablockers on fetal growth, one of our medical advisory group believes its affect on cardiac output may prevent preeclampsia. Future research, properly performed will tell. I still recommend alpha-methyl dopa for two reasons: it is the drug with the longest use and thus the longest record of relative safety, and while not confirmed may decrease mid trimester loss in chronic hypertension. More important, although the study quoted is relatively small methyl-dopa is the only antihypertensive drug that boasts a seven year follow up of the newborn, a study that stands as beacon of the type of data we should seek in every drug given to a pregnant woman.
Finally, the simplest answer to the question: We treat when levels indicate and do not withhold treatment for fear of Ã¢â‚¬Å“masking symptoms. There is not a strong consensus on the best drug, most currently favoring methyl dopa and labetalol for chronic hypertension and hydralazine and labetalol when blood pressure rises suddenly and dangerously and parenteral (intravenous or intramuscular injections are needed).
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