[Weight decrease in full-term newborns in the first 48 hours post natal]

It is known that the newborn (NB) presents weight loss immediately after birth. The magnitude of the weight loss is a controversial subject and there are no data in our sphere. Objecti ves: To determine the percentage of daily weight decrease in healthy full-term newborns in the first 48 hours of life. To specify whether factors such as gender, type of delivery, adequacy for gestational age, and use of milk formula influence weight loss.

Prospective study in healthy full-term newborns with > 37 weeks of gestational age during their stay in the nursery (puerperium). Weight data were collected at birth, 24 and 48 hours after birth, and the percentages of weight loss were calculated from the daily nursing record. In addition, gender, type of delivery, adequacy to the birth and type of feeding of the NB, either exclusive breastfeeding, artificial formula or mixed (breast milk and formula) were recorded. To standardize the measurements, weights were expressed in grams and subsequently the percentage of weight loss was calculated in relation to the birth and the previous day. The maximum percentage of weight loss per day variable was analyzed. A multivariate regression model was performed for the weight loss percentages evolution.

2960 NB were analyzed. The average weight loss on the first day was 4.43% (SD: 1.96), the second day 2.51% (SD: 1.86) and the total loss at 48 hours was of 6.85% (DS: 1.92). The determining factor in weight loss was the type of delivery. The NBs by cesarean section showed a greater weight loss in the first 24 to 48 hours. The use of milk formula determines a smaller weight loss in the NB compared with those fed with breast milk (BM).

The percentage of weight loss per day of the NB in our center is similar to that reported in the international literature. Cesarean delivery is the factor associated with greater weight loss. The use of milk formula results in less weight loss.