TT Lao

Abstract

Fetal growth is conventionally assessed by the size of the infant at birth, and a small-for-gestational age (SGA) infant is usually regarded as having in-utero growth restriction (JUGR), despite the realisation that low birthweight does not equate to IUGR. The recent finding that the placental weight to birthweight ratio (placental ratio) is increased in low birthweight and term SGA infants may provide a simple method to identify the infants with IUGR. The cause of this increase in the placental weight relative to the birthweight is thought to be placental hypertrophy as a means to compensate for the nutritional deficiency that causes the growth restriction. Nevertheless, an increased placental ratio is also found in other conditions that may not be associated with a difference in the birthweight, such as mild gestational diabetes mellitus, and anaemia due to both iron deficiency and thalassaemia trait. As well, an increased placental ratio is also associated with maternal smoking and living at high altitude. From these observations, it appears that an increased placental ratio reflects not only IUGR as such, but also the placental adaptation to environmental factors that cause fetal growth disturbance.