OBJECTIVETo study the differential facial responses to four basic tastes of the newborns and the gender-related different taste sensitivity.

METHODSSixty-two newborns (31 females and 31 males) born in the Department of Obstetrics, First Hospital of the Chongqing University of Medical Sciences were tested for responses to four solutions, including 25% sucrose (sweet), 5% sodium chloride (salt), 1.43% citric acid (sour), and 0.025% berberine (bitter) 90 minutes after birth. The inclusion criteria were: (1) medically uncomplicated full-term pregnancy; (2) medically uncomplicated spontaneous vaginal delivery; (3) Apgar score of at least 8 at 1 and 5 min. All the infants were found to be normal and healthy on pediatric examination. The facial responses of the newborns were recorded by video. The facial responses were divided into nine facial action units and expressions from A1 to C3, which are also expressed as the 1 - 9 grades of intensity, crying was included as grade 9 and nausea was defined as grade 10 intensity. The distinctions of the facial responses were analyzed by chi-square test. The distinctions of sex in the facial responses were analyzed by the Wilcoxon test.

RESULTSAll the newborns were full term, excluding the medical conditions. The average birth weight of the newborns was 3324.3 g. The data from the study indicated that absence of distinctive mouth action or sucking was the major facial response of the infants to sucrose solution (P < 0.01). There were no special expressions when the newborns were given the salt solution (P > 0.01). The lip pursing with negative brow and middle face actions were major response of the infants to the sour solution (citric acid) (P < 0.01). The expressions in response to the bitter solution of the infants were the mouth gaping with negative brow and middle face actions (P < 0.01). The facial responses to the sweet and bitter solutions in the boys were more sensitive than those in the girls (P < 0.01). There was no sex difference in the intensities of the facial responses to the salt and sour solutions (P > 0.05).

CONCLUSIONSThe newborns had distinct responses to the four solutions shortly after birth. The facial expression to sweet and bitter solutions in the boys were more sensitive than in the girls.