A new noninvasive bilirubinometer (Tc BM), which measures transcutaneous bilirubin level of the newborn, was developed as a joint effort by the present authors and the Minolta Camera Company, Ltd. A series of linear relationships were found to exist between total serum bilirubin concentration and yellowish skin color intensity in both term and low-birth-weight infants of Japanese ancestry. The instrument was examined for precision, accuracy, and technique-dependence. From these resulting relationships, it can be concluded that the transcutaneous bilirubin measurement is precise and accurate, and will become an alternative to the routine procedures used to measure serum bilirubin concentration in the near future. Although the values obtained during phototherapy or postexchange stage do not correlate well with serum bilirubin measurement, transcutaneous bilirubin will be accepted by the general nursery staffs because of its potential screening value.

We studied the relationship between rooming-in/not rooming-in and breast-feeding variables such as breast feeding frequency, breast milk intake, supplements of other human milk or 5% glucose solution, cumulative weight loss, weight recovery and hyperbilirubinemia. We found that the breast feeding frequency was significantly higher in infants rooming-in than in those not rooming-in. Intake of breast milk on days 3 and 5 was significantly lower and maximum weight loss was significantly higher in infants rooming-in than in those not rooming-in. Infants rooming-in also had less supplement of other human milk compared with non-rooming-in infants (p less than 0.01). However, the weight increase per day from minimum to weight on day seven was higher in infants rooming-in than in non-rooming-in infants (39.3 +/- 21.4 g/day vs. 31.4 +/- 15.3 g/day, p less than 0.01). The frequent suckling by rooming-in infants may explain, in part, the better weight gain, since frequent suckling may decrease energy consumption by reducing movement and crying during the early days of life, thus contributing to better weight gain. Our study suggests that some of the neonatal feeding problems related to breast feeding could be eliminated by education of mothers and nurses and by changes in hospital policies and practices in breast feeding.

Skin bilirubin (transcutaneous bilirubinometry, TcB, reading) and serum bilirubin kinetics were studied in 20 full-term hyperbilirubinemic infants during and after phototherapy. TcB readings at the chest site decreased after 2 h of phototherapy from 28.0 to 21.3 (25% of initial TcB reading, p < 0.001) and thereafter continued to decrease in a nonlinear fashion through the first 24 h of phototherapy. However, TcB readings after 12 h of phototherapy were about 50% of the initial readings (p < 0.001), declining minimally during the second 12 h of phototherapy, suggesting saturation kinetics. While serum bilirubin levels remained unchanged during the first 4 h of phototherapy, thereafter they showed a rapid decline to 12 h of phototherapy. The rate of decline decreased during the second 12 h of phototherapy, but serum bilirubin levels still decreased significantly from 16.9 to 14.9 mg/dl. Although TcB readings showed saturation kinetics during the second 12 h of phototherapy, the serum bilirubin levels were shown to decrease significantly. This suggests that the main site of action of phototherapy may be intravascular at this stage, rather than the skin and subcutaneous capillary bed as in the early stage of phototherapy.

The various physiologic factors which might influence the time of first meconium passage were studied in 62 healthy full-term newborn infants. Thirty-two babies were born vaginally and 30 by elective cesarean section. Infants born vaginally were more acidotic and passed first stool earlier compared to those born by cesarean section. The same applies to vaginally delivered babies when comparing babies born to primipara and others. Acidosis is a presumed mechanism, and a role of gastrointestinal hormones is suggested to be the possible mediator of increased motility in these babies.

The purpose of this study was to determine whether the postnatal age might affect the accuracy and reliability of transcutaneous bilirubin measurements. A total of 576 transcutaneous bilirubin measurements were performed on 336 Japanese full‐term breastfed newborn infants during the first 12 days of life. We divided them into three groups according to postnatal age and studied the effect of postnatal age on the accuracy and reliability of TcB measurements. Our study revealed that the most reliable site for transcutaneous bilirubin measurements changed from the forehead to the sternum with advancing postnatal age (i.e. forehead for0–3 days, chest for4–5 days, sternum for 6 days and later).