Betamimetics are the best-studied tocolytic drugs;
they inhibit myometrial contractions by raising the
intracellular concentration of cAMP (Figure 4). Fenoterol
has been approved for this purpose only in
Germany and Austria, where it is used in 95% of
hospitals. In other countries, ritodrine and ter -
butaline are used. According to a recent Cochrane
meta-analysis of eleven placebo-controlled trials of
ritodrine and terbutaline, these drugs prolong pregnancy
by two and seven days, respectively, but do
not lower perinatal mortality (16).