Objective: To summarize existing data about the effectiveness of bed r
est when used to improve various pregnancy outcomes and to determine h
ow often bed rest is used and the cost associated with its use. Data s
ources: We used the MEDLINE data base to search for all English langua
ge papers evaluating the effectiveness of bed rest in pregnancy. We al
so reviewed a number of textbooks and the 1988 National Infant Mortali
ty Survey. Methods of study selection: We reviewed these sources for r
ecommendations about using bed rest in various obstetric conditions. W
e used the 1988 National Infant Mortality Survey to determine how ofte
n bed rest was used either to prevent or to treat various obstetric co
nditions and estimated the costs associated with its use. Data extract
ion and synthesis: Bed rest is used in nearly 20% of all pregnancies t
o prevent or treat a wide variety of conditions, including spontaneous
abortion, preterm labor, fetal growth retardation, edema, chronic hyp
ertension, and preeclampsia. There is little evidence of effectiveness
. The estimated costs associated with bed rest, including hospitalizat
ion, lost wages, and lost domestic productivity, range from more than
$250 million to billions of dollars per year. Conclusions: Bed rest is
used extensively to treat a wide variety of pregnancy conditions, at
substantial cost but with little proof of effectiveness. We recommend
that because this intervention has failed the test of effectiveness, i
ts use during pregnancy should be curtailed unless randomized trials d
emonstrate improvement in a specific outcome.