Mid-Trimester Allostatic Load and Spontaneous Preterm Birth in a Cohort of Pregnant Women Living with HIV in Zambia.

OBJECTIVES

Maternal HIV is associated with preterm birth (PTB). In resource-rich settings, spontaneous preterm birth (SPTB) has been linked to biomarkers of stress. We examined the association between allostatic load and SPTB among women with HIV.

METHODS

In a nested case-cohort analysis of a randomized trial of intramuscular progesterone to prevent PTB in women with HIV in Lusaka, Zambia, we measured 15 midtrimester plasma biomarkers from 4 domains: cardiovascular, immune, metabolic, and neuroendocrine. SPTB was defined as delivery <37wks preceded by spontaneous labor or membrane rupture. A composite ALI was calculated by summing Z-scores from all markers (ALI-15); another was calculated from a 7 marker subset (ALI-7) with Z-score differences >0.1 between outcome groups. We estimated SPTB time-to-event curves and hazard ratios (HR) between ALI quartiles.

RESULTS

Of 800 women enrolled in IPOP (2015-2017), 51 (6%) had SPTB. We randomly selected 107 participants, including 6 with SPTB (cases). We then selected all remaining cases (n=45), yielding a final sample of 152. Z-score distributions of systolic blood pressure, heart rate, HDL, triglycerides, hemoglobin A1C, albumin, and 25-OH Vitamin D were included in ALI-7. Participants in the fourth quartile of ALI-7 were more likely to experience SPTB (HR 2.49, 95% CI 1.15-5.40) than participants in the second quartile; this association was attenuated when quartile groups were defined by ALI-15 (HR 1.24, 95% CI 0.59-2.60).

CONCLUSIONS

High ALI among women with HIV was associated with SPTB. A seven marker ALI appeared a more meaningful indicator of risk than one composed of all measured markers.