Birthweight data from 197 rural Gambian women who received an energy-dense prenatal dietary supplement over a 4-y period (net intake = 430 kcal/d) was compared with data from 182 women from 4 baseline years. Preintervention birthweights averaged 2944 +/- 43 (SEM) g when women were in positive energy balance during the dry harvest season (pregnancy weight gain greater than 1200 g/mo). Birthweights decreased to 2808 +/- 41 g (p less than 0.01) in the wet season when food shortages and agricultural work caused negative energy balance (weight gain less than 500 g/mo). There were no detectable secular trends in the baseline data. Supplementation was ineffective during the dry season but highly effective during the wet season: +225 +/- 56 g, p less than 0.001 (unadjusted) or +200 +/- 53 g, p less than 0.001 (adjusted for sex, season, and parity) by between-child multiple regression analysis; +231 +/- 65 g, p less than 0.001 by within-mother analysis. The proportion of low-birthweight babies (less than 2501 g) decreased from 23.7-7.5%, p less than 0.002. The observed threshold effect emphasizes the importance of selective targeting of interventions to truly at-risk groups.

Serologic markers of hepatitis B virus (HBV) infection were measured in children from Manduar and Keneba, two adjacent villages in The Gambia, in 1980 and in 1984. The rate of HBV infection over the 4 years differed markedly: in Manduar 71% of children who were less than 5 years of age in 1980 became infected, whereas in Keneba only 37% became infected. Male children were more frequent carriers of either HBs or e antigen than were female children. Marked clustering of hepatitis B surface antigen (HBsAg) antigenemia within sibling relationships was shown in both villages. The chance of the youngest child in a household being a carrier of HBsAg was strongly related to the number of antigen-positive siblings. Four years later, 53% of children who were initially positive for HBsAg and 33% who were positive for hepatitis B e antigen still carried these antigens. Jaundice was not observed.

Mastitis was found to be a sizeable clinical problem in a group of lactating Gambian mothers. The mean monthly incidence was 2.6% and repeated episodes of mastitis were common. The role of milk antimicrobial factors in the local defence of the breast against mastitis was investigated by analysis of IgA, IgG, IgM, C3, C4, lactoferrin and lysozyme in the breast milk of 10 mastitis patients. Acute inflammation of the breast was accompanied by the rapid appearance of high concentrations of serum-derived immunoproteins in mastitic milk. Changes in the milk levels of lactose, sodium and transferrin indicated that this was due to a temporary opening of the paracellular pathway. Concentrations of secretory immunoproteins (IgA, lactoferrin and lysozyme) exhibited a delayed response, being elevated one week after the attack of mastitis. The normal milk of mastitis sufferers was significantly deficient in IgA, C3 and lactoferrin when compared with other lactating women suggesting that the former were predisposed to mastitis.

The effects of dehydration on mechanisms of water balance and milk synthesis were investigated in ten lactating Gambian women who were fasting during Ramadan. Ten non-pregnant, non-lactating women acted as controls. Fasting consisted of total water abstention from 05.00 hours to 19.30 hours and was accompanied by high insensible water losses. Lactating women lost 7.6% of their total body water between 07.00 hours and 19.00 hours. Control subjects lost significantly less. Plasma indices of dehydration (osmolality, sodium, uric acid) showed a greater rise in the lactating women than in the control subjects over the period of fasting. However, the 19.00 hours values remained in the normal range obtained on non-Ramadan days. During Ramadan the lactating women restricted their urinary output to a lesser degree than the controls, and for much of the day their urine was also less concentrated. The lactating women appeared to have adapted by superhydrating themselves overnight. This resulted in very low urine concentrations (osmolality, sodium, urea, creatinine) in morning samples. Urine concentrations approached, but did not exceed, non-Ramadan levels by late afternoon. The daily water turnover of 6.4 litres in the lactating women was 2 litres greater than in the controls. This difference was much greater than that required for milk synthesis (500 ml) and may represent a further protective mechanism. Fasting caused changes in milk osmolality, lactose, sodium and potassium concentrations indicative of a marked disturbance of milk synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

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