guidelines no longer recommend the use of
betamimetics (5). If they are used at all, then preferably
as bolus tocolysis, which has fewer side effects
(19).
Oxytocin antagonists (atosiban) bind competitively
to the oxytocin receptor, thereby inhibiting the
oxytocin-mediated rise of the intracellular calcium
concentration that induces muscle contraction
(Figure 4). According to a current meta-analysis of
nine randomized trials, atosiban is as effective as
betamimetics with respect to the prolongation of
pregnancy and neonatal development (20), and its
side-effect rate is less than 1% (18). No fetal side effects
have been reported; the maternal side effects
are mild (headache, nausea, vomiting). A follow-up
study of infants born after tocolysis with atosiban
revealed no ill effect on their psychosocial and motor
development up to the age of two years (21).