IntroductionHuman breast milk is particularly suited to our biological needs and remains the best source of nutrition for the human infant (Kunz et al, 1999). It provides the necessary support for the development of the immune system (Goldman et al., 1994; Garofalo and Goldman, 1999). The potent anti-infective qualities of breast milk are measured by decreased infant mortality in developing countries where exclusive breastfeeding is the norm (Scariati et al, 1997; Ball and Wright, 1999). Human breast milk is about 6 percent carbohydrates, about 4 percent fat, about 1 percent protein, and about 89 percent water. The composition of human milk is very different from that of infant formula or "formula." Most artificial breast milk products use bovine milk as the substrate. The latter contains more protein and less lactose than breast milk (Kunz, et al, 1999). Lactose levels correlate well with brain size in all species. Given the large size of the brain, it is not surprising that humans have a higher concentration of lactose in milk than any other species (Newton, 2004). From the point of view of the Islamic religion, although it is recommended to prolong adequate breastfeeding up to two years, the Prophet Muhammad emphasized that the milk of pregnant women is harmful to babies and strongly advised pregnant mothers to never breastfeed their babies. The aim of this study was to compare the composition of milk in lactating mothers and non-lactating mothers to learn to what extent pregnancy might influence milk composition and how this might reflect on both the development and health of the baby. Subjects and methods I- Subjects This study was conducted on 64 healthy urban lactating women attending the outpatient clinic...... middle of paper... in the brain and 60% of this tissue is lipid (Newton, 2004 ). Stopping breastfeeding in the event of pregnancy to avoid its negative effects on breastfed newborns can expose them to many risks such as gastroenteritis and malnutrition diseases. It is therefore our responsibility to strongly advise against pregnancy during breastfeeding so that the newborn receives the best nutritional support to ensure full physical and neurological development. This is exactly what is recommended by the Islamic religion to prolong adequate lactation, up to two years, to meet the needs of the newborn and at the same time to avoid a pregnancy concomitant with breastfeeding with its negative effects on both the breastfed baby and the fetus. It is hoped that further work will be conducted to study the effect of pregnancy on other milk constituents which may also affect the breastfed baby..