Total body water in small- and appropriate- for gestational age newborns

To ascertain total body water in small for gestational age (SGA) and appropriate for gestational age (AGA) newborns.

SGA and AGA babies were matched by gestational age and studied from birth to term age. Criteria for exclusions were genetic syndromes, malformations, and congenital infections. Bioelectrical impedance was performed at two days of life (term infants), or at seven days of life and term age (preterm infants). Weight and length were measured by trained interviewers, and Z-score, weight/length ratio and Rohrer ponderal index was calculated.

Of the 54 infants evaluated, 28 were SGA (17 preterm) and 26 were AGA (15 preterm). Total body water was greater in SGA preterm babies at seven days of age (P=0.058) and at term age (P<0.0001). Weight/length ratio and Rohrer ponderal index increased towards term. Weight Z-score and anthropometric measures at term were significantly smaller in SGA babies. Being SGA and variation in Rohrer ponderal index influenced the variations in total body water.

SGA babies had greater total body water, and both groups presented insufficient increase in body solid mass, stressing the importance of nutritional support during neonatal care.