Routine prophylaxis with antibiotics does not prevent preterm birth in high risk populations according to research by van den Broek and colleagues published in PLoS Medicine.
Most pregnancies last about 40 weeks, babies born before 37 weeks of completed pregnancy are considered premature. Premature birth is a major cause of infant mortality and morbidity in high- and low-income countries. Babies born prematurely often have long-term health problems and disabilities. There are many causes of preterm birth but it has been previously shown that infection (especially ascending genital tract infection) is an important contributing factor.
This study investigated whether prophylactic antibiotics (in this case Azithromycin), given to pregnant women regardless of whether they are showing signs of infection, prevented premature birth. The researchers enrolled 2,297 pregnant women in Southern Malawi in the Azithromycin for the Prevention of Preterm Labor (APPle) study. This was a randomised, community-based, placebo-controlled trial; half the women were given azithromycin at 16-24wks and 28-32wks whilst the rest received a placebo tablet at similar times. The health of both mother (such as malarial status and anaemia) and baby (gestational age at delivery and birth weight) was monitored up to 6 wks after delivery. There were no significant differences in outcome (including preterm birth, mean gestational age at birth, mean birth weight, perinatal death and maternal anaemia) between the azithromycin and placebo groups of women. Furthermore, meta-analysis (combining results of several studies) of these results with seven other similar studies showed that prophylactic antibiotics in pregnancy had no effect on preterm birth.
Clearly, these findings do not the support the use of antibiotics as prophylaxis to prevent preterm birth. It is unknown why these results are negative given the fact that infection has been associated with preterm birth. More work is needed to determine whether different antibiotics or doses might be useful, and to identify alternative strategies for the prevention of preterm birth.
van den Broek, N., White, S., Goodall, M., Ntonya, C., Kayira, E., Kafulafula, G., & Neilson, J. (2009). The APPLe Study: A Randomized, Community-Based, Placebo-Controlled Trial of Azithromycin for the Prevention of Preterm Birth, with Meta-Analysis PLoS Medicine, 6 (12) DOI: 10.1371/journal.pmed.1000191