## 4 Discussion
In our present model, we considered that the neonate's vasomotor mechanisms were not efficient enough to influence the conservation of the heat produced by metabolic processes. Premature infants show vasoconstriction in certain regions of the body, such as the hands, feet, and calves [38,39]. [PERSON] et al. [40] indicated that peripheral vasoconstriction (which normally reduces heat loss from the skin to the environment) was relatively ineffective. Vasoconstriction at the feet was effective but was accompanied by vasodilitation at the trunk (a large proportion of the body surface area), greater dry heat loss, and, thus, an increase in the risk of hypothermia. Although our model does not take into account the physiological responses of a living organism, it has certain advantages. For example, one can accurately assess the impact of inter-infant variability in metabolic heat production and the thermal impact of the clothing used to protect the neonate in accordance with ISO standards [15,28]. To the best of our knowledge, this assessment has not previously been performed in premature neonates during SSC. Differences in body mass, gestational age, the thermal insulation of clothing, and care procedures can modify heat exchanges with the environment and, thus, mask small differences in body heat losses--especially in fairly small series with a greater probability of confounding factors. In the present study, we chose to calculate the mean body temperature because it is reportedly a reliable index of body cool stress [23; 24]. This choice was also based on older literature data [21; 22], according to which body temperature stability depends on the regulation of heat flows between the skin surface and the environment (i.e., body heat storage) rather than the body's internal temperature alone. Using a model, thus, avoids the need to measure the infant's body temperature (e.g., rectal temperature) very frequently. Although the rectal temperature is still the gold standard body temperature, it is particularly invasive in premature newborns. There is a risk of anal perforation, and vagal stimulation can lead to arrhythmia, bradycardia, and apnea [41]. Tympanic and axillary measurements are less invasive but have to be corrected, and the magnitude of the correction is subject to debate in the literature. Our study had a number of limitations. Firstly, the mannequin does not mimic convective and evaporative heat losses from the skin and the respiratory system, which have to be estimated mathematically (Equations (2), (3) and (5)). One of the determinants of skin evaporation is the fraction of body area that is wetted, which is based on a very old literature value from a study in adults [30]. This value is probably an underestimate in neonates, whose thin skin lacks keratin and is very permeable to water vapor [42]. Secondly, our model did not take into account changes over time in the thermal states of the mother and the neonate; we considered solely the variables known or assessed at birth. It would be interesting to measure changes over time in the skin temperature of the mother's trunk using infrared thermography. To the best of our knowledge, there are no literature data on these determinants of heat losses.