Effect of maternal HIV status on breast milk intake and growth of HIV-uninfected Kenyan infants at 6 weeks post-partum and 6 months of age
Background: All infants irrespective of their HIV status and that of their mothers should be exclusively breastfed in their first half of infancy. It is however not well known if infants‟ exposure to maternal HIV infection does affect their breast milk intake, linear growth and body composition. Objectives: To compare breast milk intake of HIV-uninfected infants born of HIV-positive mothers with that of infants born of HIV-negative mothers at 6 weeks and 6 months of age. Additionally, the study aimed to assess the effect of maternal HIV status on infant growth, body composition (lean mass) and breastfeeding practices among the mothers. Methods: A prospective cohort study with cross sectional data collection at 6 weeks and 6 months post-partum. The study was based at the Maternal and Child Health Clinic of Siaya County Referral Hospital in the Lake Region of Western part of Kenya. Seventy five (75) HIV-1 positive and 68 HIV-1 negative mothers with HIV-uninfected infants were systematically sampled and recruited with their infants at 6 weeks post-partum and followed up at 6 months after birth. At recruitment and follow-up, mothers and their infants were tested of HIV. Excluded mother-infants dyads were those with preterm infants, infants <2500g, infants not able to breastfeed and mother or infants who were severely ill. Breast milk intake was measured using the deuterium dose-to-mother technique (isotopic technique) in which pre-dose (baseline) saliva samples were obtained from both the infant and the mother on day 0. Subsequently, baseline saliva collection, a 30g dose of deuterium oxide was given to the mothers. Post-dose saliva samples were collected from both infant and mother over 14 days on days 1, 2, 3, 4, 13 and 14. Infant length, weight and skin fold thickness (growth) were measured. Fat mass and fat free mass (body composition) was measured using deuterium-dose-to-the-infant technique in which a pre-dose saliva sample was collected from the infant after which a deuterium oxide dose (0.5g/kg body weight) was administered and post-dose saliva samples collected at 3 and 4 hours post-dose. To measure both infant breast milk intake and lean mass, deuterium oxide enrichment in saliva was measured using Fourier Transform Infrared (FTIR) Spectrophotometer. Total body water from the FTIR measurement was converted to breast milk water xvii volume and lean mass using standard equations and assumptions. Other data were collected using a standard questionnaire and included socio-economic data, demographic characteristics, infant feeding practices and care practices and infant and maternal anthropometries. Results: There were no significant differences in breast milk intake between the two groups at 6 weeks and 6 months. At 6 weeks postpartum infants born of HIV positive mothers (HIV-EU) consumed 717g/day of breast milk and this was comparable to 712.6g/day consumed by infants born of HIV-negative mothers HIV-U (p=0.86). At 6 months after birth HIV-EU consumed 960.8g/day of breast milk while HIV-U consumed 963.1g/day and the two intakes were comparable (p=0.95). Factors positively associated with breast milk intake among HIV-uninfected infants were maternal BMI (r=0.247 at 6 weeks), maternal lean mass (r=0.270 at 6 weeks and r=0.365 at 6 months), infant birth weight (r=0.345 at 6 weeks) and infant current weight (r=0.486 at 6 weeks and r=0.557 at 6 months). At 6 weeks postpartum, the deuterium oxide determined exclusive breastfeeding was comparable between HIV-positive mothers (23.3%) and HIV-negative mothers (14.5%), p=0.21. At 6 months after birth the deuterium oxide EBF rates were significantly different (p=0.025) between the HIV-positive (43.3%) and HIV-negative mothers (24.2%). The self-recalled EBF rates were 4 times and 5 times higher than isotopic determine figures for HIV-EU and HIV-U respectively at 6 weeks postpartum. At 6 months after birth, the factors reduced to 1.7 and 2.5 times for HIV-EU and HIV-U respectively. At 6 weeks post-partum, there were significant differences between HIV-exposed uninfected and HIV-unexposed infants in length-for-age Z scores (1.0 for HIV-EU and 0.6 for HIV-E, p=0.011). At 6 months of age, there were no differences in mean LAZ (-1.2 for HIV-EU and -0.9 for HIV-U, p=0.154). There was no significant difference in infants lean mass and fat mass both at 6 weeks and 6 months of age. HIV-EU and the HIV-U had comparable fat free mass (5.7kg for HIV-EU and 5.9 kg for HIV-U, p=0.10), fat mass (1.6kg for HIV-EU and HIV-U, p=1.0), % fat mass (22.3% for HIV-EU and 21.3 for HIV-U, p=0.34), fat free mass index (14.7 kgm-2 for HIV-EU and 14.5 kgm-2 for HIV-U, p=0.73) and fat mass index (4.3 kgm-2 for HIV-EU and 4.0 kgm-2 for HIV-U, p=0.35). Among infants born of HIV-positive mothers, those xviii whose mothers were on ART had lower free fat mass (5.4kg verses 6.0kg for non-ART, p=0.018), and conversely higher % fat mass (24.0% versus 19.3% for non-ART, p=0.04) and lower free fat mass index (14.2kg verses 16.0kg for non-ART, p=0.076). Conclusions: Within the exclusive breastfeeding age bracket in resource poor settings, maternal HIV status does not influence the breast milk intake of HIV-uninfected infants. Infants of HIV-positive mothers are however more likely to be exclusively breastfed compared to infants of HIV-negative mothers. Maternal recalls tend to over-estimate exclusive breastfeeding rate when compared to deuterium oxide dilution technique. Interventions that ensure normal maternal body mass index, maternal lean mass, infant size (birth and current weight) are important in increasing breast milk intake which is in turn important in promoting growth and lean mass of HIV-uninfected infants. Recommendations: Validation of self-reported EBF practices with the low-cost, non-invasive deuterium oxide dilution technique is highly recommended to facilitate more effective breastfeeding promotion campaigns. Intensify breastfeeding messages among the HIV-negative mothers. They have been shown to exclusively breastfeed less as compared to the HIV positive mothers. Interventions that ensure normal maternal body mass index, maternal lean mass, infant size (birth and current weight) should be scaled-up to increase breast milk output and for better infant growth and body composition. Health workers should re-enforce antenatal and postnatal counselling for mothers regardless of HIV-status. Study found higher exposure to counselling by HIV-positive mothers and higher EBF rates among this group.The finding that infants of mothers on ART showed lower lean mass may need further investigation with a specific study designed to detect the variations. There is need for formulating Kenya-specific % fat prediction equations for infants. This will lead to a better understanding of the body composition of Kenyan infants in a wider scale.