The use of certain drugs to delay preterm labor is associated with a high rate of serious adverse reactions, finds a study published on bmj.com today.
Preterm labor is the main cause of perinatal illness and death (the period just before, during or shortly after birth) in the developed world.
Tocolytic drugs are used to delay delivery for up to 48 hours. This allows time for doctors to give steroids to speed up the baby's lung development and to enable the mother to be transferred to a centre with a neonatal intensive care unit.
Drugs most often used include beta agonists and nifedipine (to relax smooth muscles including the uterus) and atosiban and indometacin (to inhibit hormones involved in labor). But it is still unclear whether tocolysis is safe for both mother and baby, so the use of these drugs to stop labor remains controversial.
So researchers assessed the incidence of serious maternal complications in 1,920 women treated with tocolytic drugs for preterm labor at 28 hospitals in the Netherlands and Belgium. The most commonly used drug was atosiban (42%), followed by nifedipine (34%), beta agonists (14%), and indometacin (8%).
Over an 18 month period, all adverse reactions were recorded and classified as either serious or mild and according to how the drugs were given (singly, combined, or sequentially).
The overall incidence of adverse effects was low (0.7%) but combined treatment or a single treatment with a beta agonist led to a higher incidence of serious adverse drug reactions. No serious reactions were reported for atosiban or indometacin.
Atosiban had the best safety profile but is considerably more expensive than nifedipine.
Based on their findings, the authors suggest that combined treatment and treatment with beta agonists should be discouraged. They also call for further trials to test the effectiveness and safety of nifedipine and atosiban.
In an accompanying editorial, researchers say that this study serves as a timely reminder that the decision to use tocolysis should not be taken lightly. "After 30 years of research we still do not know whether tocolysis benefits the fetus, so the choice of which drug to use remains a secondary question. The real dilemma is whether or not we should treat at all," they write.
The old assumption that "keeping the baby inside longer must be a good thing" can no longer go unchallenged, they conclude.