Developmental Origins of Health & Disease (DOHaD) Lay summaries

Identification of genes controlling growth before and after birth

Keywords: development, growth, genetics, obesity, hormones

What is already known about this subject:

  • Human growth during the antenatal (before birth) and postnatal (after birth) periods depends on hormones including insulin, growth hormone, and insulin-like growth factors (IGF-1 and IGF-2).
  • Insulin-like growth factors exist within a complex system that includes receptors (which translate the IGF ‘message’ to cells), binding proteins (which help IGF bind to the receptors) and degrading enzymes (which free up the IGF receptors once the IGF ‘message’ has been passed into cells).
  • While it is known that the IGF system is important in controlling growth, it is not known how variations in the IGF genes affect growth from birth to adolescence, and whether any of these genes contribute to childhood obesity.

What this Raine study adds:

  • DNA data describing variations in nine genes within the IGF system and measures of fetal size (head circumference, abdominal circumference, femur length) and postnatal height and weight between 1 and 17 years of age in Raine participants (and confirmation in a population from the Netherlands) showed that 40% of the gene variants examined were associated with antenatal growth and 38% with postnatal growth.
  • Most of the associations with growth were associated with genetic variation in the IGF receptors.
  • Further understanding of the role of the IGF system in controlling growth could lead to lifestyle modifications in children whose antenatal growth patterns and genetics put them at the greatest risk of obesity.

Parmar, P G, J A Marsh, H Rob Taal, M Kowgier, A G Uitterlinden, F Rivadeneira, L Briollais, et al. 2013. “Polymorphisms in Genes within the IGF-Axis Influence Antenatal and Postnatal Growth.” Journal of Developmental Origins of Health and Disease 4 (2) (April): 157-69. doi:10.1017/S2040174412000633. [publink]

Fetal weights estimated from ultrasound scans are a useful addition to models of optimal birth weight in babies born prior to 30 weeks gestation

Keywords: fetal growth, preterm delivery, birth weight, ultrasound scans

What is already known about this subject:

  • When a baby is expected to be born preterm, it is important to be able to accurately estimate their birth weight in order to prepare the appropriate medical care.
  • Estimating the birth weight of a baby involves the use of mathematical models based on the birth weights of infants born at different gestational ages.
  • Because babies born preterm are often smaller than they should be for their gestational age, the standard models used to estimate birth weight are often inaccurate and underestimate an infant’s ideal or ‘optimal’ birth weight.
  • Fetal weight can be estimated from ultrasound scans, and including this data in the models used to estimate optimal birth weight may help improve their accuracy.

What this Raine study adds:

  • Fetal weight data from prenatal ultrasounds together with birth weight and gestational age data from Raine participants was used to create two statistical models for optimal birth weight; i) optimal birth weight derived from birth weight data only, and ii) optimal birth weight derived from both fetal weight and birth weight data. Including fetal weight in the model was important when estimating the optimal weight of babies born prior to 30 weeks gestation.
  • The two models were indistinguishable from 30 weeks gestation, so either model is appropriate in babies born after 30 weeks.
  • Estimates of birth weight in babies born before 30 weeks gestation should be performed using models that incorporate fetal weight data as well as birth weight data.

Pereira, G., Blair, E., & Lawrence, D. (2012). Validation of a model for optimal birth weight: a prospective study using serial ultrasounds. BMC Pediatrics, 12(1), 73. doi:10.1186/1471-2431-12-73. [publink]