Birth weight and preterm delivery outcomes of vertically vs non-vertically infected HIV positive pregnant women

Uninfected infants born to vertically infected HIV positive women might be at greater risk for lower birth weight than those born to non-vertically infected women, according to findings from the largest cohort of pregnant women to date.

This evaluation also suggested that although infants born to vertically infected women might be at greater risk, the absolute difference was small. Infants born to vertically infected women did not appear to be at increased risk for small for gestational age or preterm birth outcomes.

Data from a combined analysis of pregnant women and their uninfected infants enrolled in the Paediatric HIV Cohort Study (PHACS) Surveillance Monitoring for ART Toxicities Study (SMARTT) and IMPAACT P1025 protocol – conducted to assess whether maternal perinatal infection and adverse could be associated with adverse infant outcomes – were shown at AIDS 2016.

The study looked at HIV positive women aged 13-30 years with singleton births enrolled in the two cohorts in US and Puerto Rico 1998-2013, for which birth weight, gestational age and maternal mode of HIV transmission data were available. Infant outcomes were compared between those born to vertically and non-vertically infected women.

Overall, 2270 women delivered 2692 infants: 270 born to vertically infected and 2422 to non-vertically infected women. Vertically infected women: were younger (mean age 21 vs 25 years); less often black (55% vs 67%); more likely to have CD4 count <200 cells/mm3 at enrolment (19% vs 11%); more likely to have viral load >400 copies/mL at delivery (28% vs 23%); more likely to receive a >3-class ART regimen during pregnancy (23% vs 2%); more likely to have pre-pregnancy BMI <18.5 kg/m3 (6% vs 3%); less likely to report tobacco (14% vs 20%) and substance use (1.7% vs. 3.3%) during pregnancy. All comparisons p<0.01.

After adjustment (age, ethnicity, pre-pregnancy BMI, tobacco use, substance use, CD4 and maternal ART) mean birth weight z-score was lower in infants of vertically compared with non-vertically infected women: adjusted difference -0.13 (95% CI -0.24 to -0.01), p=0.03. Ethnicity, pre-pregnancy BMI, tobacco and substance use were also risk factors for low birth weight.

In this large American study, the investigators found no associations between maternal vertical transmission status and pre-term delivery or small for gestational age.

They concluded that future studies are warranted to understand mechanisms by which the intrauterine environment of vertically infected women might affect foetal growth.

Jao J et al. Birth weight and preterm delivery outcomes of perinatally vs. non-perinatally HIV-infected pregnant women in the U.S.: results from the PHACS SMARTT study and IMPAACT P1025 protocol. 21st International AIDS Conference. 18-22 July 2016. Durban South Africa. Oral abstract WEAB0105.
http://programme.aids2016.org/Abstract/Abstract/736 (abstract)
http://programme.aids2016.org/Programme/Session/972 (webcast)