Objective

To estimate the association between duration of combination antiretroviral therapy (cART) during pregnancy and low infant birthweight (LBW), among women ≥37 weeks gestation.

Design

We conducted a retrospective cohort study of HIV-infected women who met eligibility criteria based on CD4 count ≤350 but had not started cART at entry into antenatal care (ANC). Our cohort was restricted to births that occurred ≥37 weeks gestation.

Methods

We used Poisson models with robust variance estimators to estimate risk ratios (RR) and 95% confidence intervals (CI).

Results

Of 50,765 HIV-infected women with antenatal visits between January 2009 and September 2013, 4,474 women met the inclusion criteria. LBW occurred in 302 pregnancies (7%). Nearly two-thirds of women (62%) eligible to initiate cART never started treatment. Overall, 14% were on cART for ≤8 weeks, 22% for 9-20 weeks, and 2% for 21-36 weeks. There was no evidence of an increased risk of LBW for women receiving cART for ≤8 weeks (RR 1.22, 95% CI: 0.77, 1.91), 9-20 weeks (RR 1.23, 95% CI: 0.82, 1.83), or 21-36 weeks (RR 0.87, 95% CI: 0.22, 3.46), compared to women who never initiated treatment. These findings were consistent across several sensitivity analyses.

Conclusions

Longer duration of cART was not associated with poor fetal growth among term pregnancies in our cohort. However, the relationship between cART and adverse pregnancy outcomes remains complicated. Continued work is required to investigate causality. An understanding cART's impact on adverse pregnancy outcomes is essential as cART becomes the cornerstone of PMTCT programs globally.