Reasons Why Newborn Babies Lose Weight After Birth

Newborns, when properly fed, grow at remarkably rapid rates. However, in the first two weeks following birth, they may fail to gain -- and indeed, often lose -- weight. This might be a source of distress to first-time mothers who are often breast- or formula-feeding their babies. However, this phenomenon is completely normal and is not a cause for concern. Though newborns are growing during this period, they are merely shedding weight in the form of excess fluid.

Weight at Birth

A term pregnancy is one that goes until 38 to 40 weeks. The normal birth weight of infants born at term is 6 to 9 lbs. A number of conditions can affect the normal birth weight of a baby. Babies born to diabetic mothers, for example, may be heavier; babies born to mothers who are poorly nourished, smokers and who are younger or older in age may be born underweight. Preterm babies — those born before 38 weeks of pregnancy — are more likely to be low in weight; post-term babies — born after 40 weeks — may weigh more.

Reasons for Weight Loss

One factor that determines a babies' birth weight is fluid content. Babies have some extra fluid present at birth. Term babies tend to have a lower fraction of extra fluid compared to preterm babies, Dr. Jochen Profit explains. After a baby is born, some of this extra fluid is excreted in the urine. Babies may lose about 7 to 10 percent of their body weight in the first few days after birth. They often reach their original birth weight at about 10 to 14 days of life.

Weight Gain

While newborns are losing weight because of fluid loss, they continue to grow during this period. After they return to their birth weight by their 10th day, they begin to gain weight rapidly, growing at about 5 oz. per week. Many newborns go through a rapid growth phase between the seventh to 10th day of life and between the third to sixth week of life.

Recommendations

Mothers should expect their baby to lose some weight after birth; this does not mean your baby is sick or malnourished. According to "Nelson's Textbook of Pediatrics," "feeding can be considered to have progressed satisfactorily if the infant is no longer losing weight by the end of the first week of life and is gaining weight by the end of the second week." Newborns are frequently weighed during their hospital stay and may be measured two to three days following their discharge, one week after birth and two weeks after birth. If there is any abnormal weight loss, mothers should alert their pediatrician to these findings.