Several studies in pregnant women have shown an association between low maternal vitamin D and preterm birth. HIV and antiretrovirals (ARVs) can affect vitamin D levels. Few studies have assessed the relationship between maternal vitamin D and preterm birth in HIV+ pregnant women.
We evaluated data from Latin American HIV+ pregnant women enrolled in the National Institute of Child Health and Human Development (NICHD) International Site Development Initiative (NISDI) cohort from 2002-2009. Preterm birth was defined as delivery at <37 weeks (wks) gestational age (GA). Maternal plasma 25-hydroxyvitamin D (25OHD) levels were measured using the Abbott Architect® immunoassay on stored samples collected at 12-34 wks GA. Severe vitamin D deficiency was defined as 25OHD <10 ng/mL, deficiency as 10-20 ng/mL, insufficiency as 21–29 ng/mL, and sufficiency as >30 ng/mL. Logistic regression modeling was used to evaluate the effect of maternal vitamin D on preterm birth.
Of 715 HIV+ women, 13 (1.8%) were severely vitamin D deficient, 224 (31.3%) deficient, and 233 (32.6%) insufficient. Severely deficient women had lower rates of no ARV use for >28 days prior to the date of vitamin D testing compared to deficient, insufficient, and sufficient women (15.4% vs. 55.4%, 49.4%, and 39.2% respectively) and higher rates of non-nucleoside reverse transcriptase inhibitor use (46.2% vs. 17.4%, 17.6%, and 16.7% respectively, p<0.01). Overall, 23.2% (166/715) of pregnancies resulted in preterm birth [median GA of preterm births=36 wks (Interquartile Range: 34-36)]. After adjusting for age, substance use in pregnancy, CD4 count, HIV RNA level, body mass index (BMI), ARV use in pregnancy, pre-eclampsia/eclampsia, and prior preterm birth, severe vitamin D deficiency was associated with preterm birth [adjusted Odds Ratio (aOR)=4.7, 95% Confidence Interval (CI): 1.3-16.8)]. In stratified analyses, these results remained the same amongst women with vitamin D testing at <22 wks GA (aOR=2.7, 95%CI: 1.1-6.7) and those with vitamin D testing at >22 wks GA (aOR=7.0, 95%CI: 1.6-30.9). In addition, pre-eclampsia/eclampsia (aOR=5.8, 95%CI: 2.3-14.7), underweight maternal BMI (aOR=1.8, 95%CI: 1.1-3.0), and prior preterm birth (aOR=2.7, 95%CI: 1.6-4.6) were also associated with preterm birth.
HIV+ women with severe vitamin D deficiency may be at risk for preterm delivery. Further studies may be warranted to determine if vitamin D supplementation in HIV+ women may impact risk of preterm birth.