Analysis of Head Circumference, Birth Weight and Birth Length in Japanese triplets
Objective: The aims of this study were to analyze body size parameters at birth, especially head circumference, according to gestational age, and identify factors associated with birth weight, birth length and head circumference for triplets.
Methods: The subjects of this study were 370 mothers and their 1,109 triplet children who were born between 1978 and 2002. For these births, data on birth weight, birth length, head circumference, gestational age, sex, parity, maternal age at delivery, year of delivery, maternal pregravid weight and maternal height were obtained from records in the Maternal and Child Health Handbooks.
Results: Compared to the standard for Japanese singleton neonates, the median head circumference of triplets was almost the same. The median head circumference of male neonates was approximately 0.5 cm longer than female neonates. Concerning factors associated with birth weight, birth length and head circumference in triplets, the gestational age proved to be the strongest contributing factor to birth weight, birth length and head circumference of the triplets. Moreover, sex was a significant factor affecting birth weight, birth length and head circumference. Male neonates had a higher birth weight, longer birth length and greater head circumference than female neonates. Birth order in triplets also had a significant effect on birth weight and head circumference. Lower birth order neonates had a higher birth weight and greater head circumference. An effect of maternal pregravid body mass index (BMI, kg/m2) on both birth weight and birth length was observed.
Conclusions: The deficit of head circumference for triplets is very small compared with that of singletons. Moreover, the gestational age, sex, birth order in triplets and maternal pregravid physique were significant factors affecting body size parameters at birth of triplets.