Are babies getting bigger? Secular trends in fetal growth in Israel--a retrospective hospital-based cohort study.

BACKGROUND A paradoxical secular trend of an increase in preterm births and a decrease in low birth weights has been reported in many developed countries over the last 25 years. OBJECTIVE To determine if this trend is true for Israeli neonates, and to add new information on secular trends in crown-heel length and head circumference. METHODS A hospital-based historic cohort design was used. Anthropometric data for 32,062 infants born at Rabin Medical Center in 1986-1987, 1994-1996, and 2003-2004 were collected from the hospital's computerized registry and compared over time for absolute values and proportional trends. RESULTS For the whole sample (gestational age 24-44 weeks) there was a significant increase in mean birth weight (by 41 g), crown-heel length (by 1.3 cm), and head circumference (by 0.1 cm) from 1986 to 2004 (P < 0.001). A similar trend was found on separate analysis of the post-term babies. Term infants showed an increase in mean length and head circumference (P < 0.001), but not weight, and moderately preterm infants (33-36 weeks) showed an increase in mean weight (81 g, P < 0.001) and mean length (1.0 cm, P < 0.001), but not head circumference. The proportion of post-term (42-44 weeks), preterm (24-36 weeks), very preterm (29-32 weeks), extremely preterm (24-28 weeks), low birth weight (< 2500 g) and very low birth weight (< 1500 g) infants decreased steadily and significantly over time (P < 0.002). CONCLUSIONS Babies born in our facility, term and preterm, are getting bigger and taller. This increase is apparently associated with a drop (not a rise) in the proportion of preterm infants. These results might reflect improvements in antenatal care and maternal determinants.