For several years, the generally accepted period for physiological weight loss is1 to 3 days, and in response, many neonates are biochemically evaluated or receive supplemental feeding support. Neonatal weight loss is normal after delivery with an expected loss of 5% to 7% of birth weight. Neonates usually stop losing weight by day 5 following birth, and typically regain their birth weight by 1 to 2 weeks of age. Flaherman et al. (
8) were the first to report an early weight loss nomogram for exclusively breastfed neonates.
Figure 2 shows curves for weight loss by delivery method. Mean weight loss was 4.2% at 24 hours, 7.1% at 48 hours, and 6.4% at 72 hours after birth. The maximum level of weight loss occurred at 48 hours (7.1%). Weight gain began to rise after 48 hours for infants born vaginally. Mean weight loss was 3.8% at 24 hours, 5.8% at 48 hours, and 5.1% at 72 hours after birth for the vaginally delivered infants.
Bernini et al. (
9) composed useful weight-loss charts in a report featuring a 5-year cohort of 1760 healthy term, exclusively breastfed, newborns in an Italian birth center, whose feeding policies followed the WHO’s 10 steps to successful breastfeeding standards. An analysis of weight measurements at set time points revealed a mean weight loss of 5.95%, with the peak occurring at 43.7 hours after birth (
9). It is noteworthy that this mean weight loss was significantly lower than the 6.7% in a Portuguese study featuring a large heterogeneous cohort, which reported that infants began to gain weight earlier (
10). None of the newborns in the Italian cohort lost more than 10% of their birth weight, compared to 6.1% in the Portuguese cohort (
9). Macdonald et al. (
11) reported the mean percentage of weight loss and also the day on which weight regain began in average as 2.7 and 8.3 days, respectively. Manganaro et al. (
12) noted that infants in their study born vaginally reached their lowest weight between days 3 and 4, while infants delivered by cesarean section reached their lowest weight between days 4 and 5. There is evidence that the initiation rates of breastfeeding are lower in infants delivered by cesarean section compared with the ones born vaginally (
13,
14). Mean weight loss after delivery by cesarean section was 4.9%, 8%, 8.6%, and 5.8% at 24, 48, 72, and 96 hours, respectively. Weight gain began after 72 hours in newborns delivered by cesarean section (
8). The present study observed that weight loss was statistically higher in newborns delivered by cesarean section compared with the ones born vaginally, at 24, 30, and 72 hours. Differences were not detected in other measurements. Mean weight loss in the present study was 4.59%, 6.0%, and 6.95% at 24, 48, and 72 hours after birth in newborns delivered by cesarean section. However, the present study found no significant difference in the early-period weight loss based on the nationality. For all infants, the hospital labor ward applied the WHO’s 10 steps to successful breastfeeding standards. Similar to the present study, Flaherman et al. (
8) reported no difference in the early weight loss of breastfed newborns according to gender. This degree of weight loss could be related to high risk of pathological features and hypernatremic dehydration, requiring supplementation intervention, although it should be avoided since it may discourage the initiation of breastfeeding and decrease its duration (
4,
15). Initiation of supplementation with banked human milk or commercial infant formula is only recommended when the infant has lost more than 7% of neonatal birth weight between 5 and 10 days of age when the infant exhibits signs of dehydration and the mother’s milk supply is limited (
16). All newborns were exclusively breastfed in this study, no supplementation was initiated.
As a result, according to the study of healthy term newborns, ethnicity and gender differences did not affect weight loss. Depending on early birth by cesarean section or vaginal delivery, maximum weight loss in newborns occurred after 42 hours in vaginal delivery vs. 72 hours in cesarean delivery. Being aware of the daily weight loss rate of dehydration can prevent complications and unnecessary supplementation.