PHILADELPHIA, PA — Women who are HIV positive and pregnant have high rates of preterm delivery (PTD) and deliver children who are small for gestational age (SGA) in Canada, a study reported at IDWeek 2014.

“A modifiable risk factor may be the type of antiretroviral regimen used, as an increased risk of preterm delivery was seen in association with the use of ritonavir-boosted regimens,” noted Fatima Kakkar, MD, MPH, of CHU Sainte-Justine, Université de Montréal, Montréal, Quebec, Canada.

Noting that the rate of PTD among women who are HIV-positive and the possible association with use of antiretroviral therapy during pregnancy remains a subject of debate, Kakkar and colleagues identified mother-infant pairs from the Canadian Perinatal HIV Surveillance Program, which actively captures data on perinatal HIV exposure from 22 sites in Canada annually, to determine if risk factors for PTD and SGA could be identified.

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PTD was defined as <37 weeks gestational age, and SGA was defined as weight less than the 10th percentile for age. Multivariate regression was used to adjust for variable known risk factors for PTD, and accounted for dependence between multiple pregnancies of the same woman.

Between 1987 and 2013, the overall incidence of PTD was found to be 16.26% (427 of 2,626 births), compared to a rate in Canada of 8%. The overall incidence of SGA was 20.48%.

Significant risk factors for PTD included maternal race (aboriginal vs. white race; OR 1.65; P=0.002), HIV acquisition risk factor (intravenous drug use vs. heterosexual transmission; OR 2.17, P<0.001), and start time of ART (28–36 weeks vs. 13–20 weeks).

Among women treated with antiretroviral therapy, an increased risk of preterm delivery was observed among those treated with boosted vs. unboosted protease inhibitors (aOR 1.58, P=0.004). In particular, this was observed among women who started boosted protease inhibitors at 21–27 weeks compared with 13–20 weeks (aOR 3.17, P=0.01).

In the multivariable analysis adjusting for maternal race, HIV acquisition risk factor and antiretroviral therapy start time, risk of preterm delivery associated with the use of boosted protease inhibitors remained statistically significant (aOR 1.54; P=0.014). No association between SGA and antiretroviral therapy exposure was observed.

“A modifiable risk may be the type of ART regimen used, as an increased risk of PTD was seen in association with the use of ritonavir boosted regimens,” concluded Kakkar, and suggested that “further study is needed to discern the effect of ART regimen versus start time.”

This article originally appeared on MPR