The effect of pasteurisation on the composition of expressed human milk from HIV positive mothers, and its adequacy in relation to the growth of their very low birth weight premature infants

Van Wyk, Elisna (2008-12)

Thesis (MNutr (Interdisciplinary Health Sciences. Human Nutrition))--Stellenbosch University, 2008.


Objective: Primary: To investigate the effect of pasteurisation on the composition of expressed breast milk from HIV positive mothers and its adequacy in relation to the growth of their VLBW premature infants. Methods: A descriptive, prospective case-controlled pilot study was performed in 3 regional state hospitals in the Western Cape, South Africa. The control and study groups consisted of 12 HIV negative and 11 HIV positive mothers, with their VLBW premature infants, respectively. All mothers (19 - 35 years old) belonged to the Xhosa ethnic group. All infants were born <34 weeks gestation and birth weight <1500g. Eight breast milk samples were collected on days 6, 7, 13, 14, 20, 21, 27 and 28 from all mothers during the first 28 days after birth. Breast milk was expressed by hand or pump from either the right or left breast. Half of each breast milk sample was kept raw. The remaining sample was Pretoria pasteurised, after which both samples were subdivided into 3 or 4 aliquots to determine energy, protein, carbohydrate, fat, folate, calcium, phosphorus, magnesium, sodium, otassium, iron, copper, zinc content and HI viral load (study group only). The mothers’ dietary intake during pregnancy and lactation was obtained by means of a quantitative food frequency questionnaire and repeated 24-hour recall respectively. The infants’ dietary intake was recorded daily. Mothers’ anthropometric measurements taken at study entry and exit were weight, height and mid-upper arm circumference. All infants’ daily weight, as well as length and head circumference at birth and on day 28 postpartum was obtained. Biochemical analysis was performed on the blood samples obtained at study entry and exit from all mothers and infants. For statistical analysis, Statistica® (release no 7, 2006) was used for repeated measures analysis of variance (ANOVA) to determine the effect of HIV, pasteurisation, milk expression and time on the composition of the breast milk. Results: There was no significant difference in the studied macro- and micronutrient composition between raw or pasteurised expressed breast milk from HIV positive and HIV negative mothers with premature infants. A significant decline in breast milk protein (p<0.01), magnesium (p=0.045), potassium (p=0.002), zinc (p<0.01) and copper (p=0.03) content was observed for the whole study population over time, while folic acid content increased significantly (p=0.012) over time. The sodium/potassium ratio of both groups remained strongly indicative of the presence of sub-clinical mastitis. A significant (p=0.03) greater mean volume of milk was obtained with pump [42.5 Standard Deviation (SD) 18.1 ml], compared to hand expression [36.7 (16.7) ml]. Method of expression did not result in a significant difference in breast milk composition for any of the nutrients studied. Eight (35%) infants were born SGA while 21 (91%) infants were SGA on day 28. The infants gained a mean of 16.37 (4.5) g/kg/day (i.e. 91% of the recommended growth rate of >18g/kg/day) from the day on which birth weight was regained. The control and study group infants respectively consumed a mean of 3.27 (1.36) and 3.21 (1.36) g protein/kg/day and 138.1 (33.8) and 142.3 (33.8) kcal total energy/kg/day. This corresponds to a PER of 2.6 (control group) and 2.5 (study group) respectively, which cannot provide for the increased growth needs of the SGA infant in need of catch-up growth. Six infants experienced an incident of Grade 1 NEC which resolved and all completed the study. Two (18%) HIV-exposed infants were found to be HIV positive at 28 days post delivery. Four participating infants died. No adverse event or mortality was related to the study protocol as no intervention was undertaken. Conclusion: HIV positive Xhosa mothers provide as nutritious breast milk to their VLBW premature infants as HIV negative Xhosa mothers. Maternal nutrient intake during pregnancy and lactation did not have a significant effect on the nutritional composition of breast milk, except for folate content.

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