Longitudinal Studies of Breast Milk Zinc Transfer to Appropriate- and Small-for-gestational-age, Predominantly Breast Fed, Bangladeshi Infants

The International Atomic Energy Agency (IAEA) has reviewed published literature to collect information for its Coordinated Research Project (CRP) on Zinc Nutrition During Early Life , and observed that there is limited information on: 1) the concentration of zinc in breast milk of mothers in lower income countries at different times post-partum; 2) the total amount of zinc transferred from mothers to infants at different ages in these settings, and 3) zinc transfer from mother to infant born with appropriate-for-gestational-age (AGA) and small-for-gestational-age (SGA). Therefore, IAEA has planned to assist local scientists to collect such information from selected countries. The International Zinc Nutrition Consultative Group (IZiNCG) has identified Bangladesh as a country with high risk of zinc deficiency (IZiNCG, 2004), where the rate of SGA infants is >30% - one of the highest in the world (de Onis, 1998). Thus, Bangladesh is an appropriate candidate country to participate in this CRP.

This study will enroll 50 healthy, full-term, newborn infants (>37 weeks gestational age by ultrasound) and their mothers if they plan to breast-feed exclusively for at least 4 months and also to continue breast feeding for at least 12 months. The infants will be examined, weighed and measured within 48 hours of birth, half of whom will be AGA (BW>2800g) and the other half SGA (BW<2500g). Infants with any acute or chronic illnesses, or congenital anomalies will not be eligible. Any mother with toxaemia, pregnancy-induced hypertension, multiple pregnancies, previously diagnosed as positive for HIV/hepatitis B infections, or habituated to smoking or alcohol consumption will also be excluded. The participants will be recruited from Nandipara, Dhaka, an urban community where the ICDDRB has ongoing clinical study facilities.

Each of the eligible mother-infant pairs will be studied in 3 separate rounds, at 4, 12 and 24 weeks post-partum. In each round, two-week studies of breast milk transfer from the mother to the infant will be carried out, using the deuterium "dose-to-the-mother" technique. In each round, the women will be requested to attend the Dhaka Hospital of ICDDR, B on day 0, for collection of baseline saliva samples from mother-infant pairs and administration of deuterium to the mothers. Study health workers will make home visits on days 1, 2, 3, 4, 13, and 14 and collect saliva samples from the infants and their mothers on days 1, 2, 13 and 14, of each round.

~2 ml of saliva will be collected for each sample from both the mother and the infant.

On days 0 and 4 of each round, 5-10 ml of manually-expressed breast milk will be collected for determining their zinc concentration. The total zinc transfer from mother to infant will be calculated as the product of the mean daily milk volume, as determined from the deuterium studies, and the mean milk zinc concentration on the days of milk collection.