Expression of insulin-like growth factor-I and placental growth hormone mRNA in placentae: a comparison between normal and intrauterine growth retardation pregnancies.

Intrauterine growth restriction (IUGR) is generally defined as the pathological restriction of fetal growth resulting in a fetus with birth weight below the 10th percentile for gestational age. Almost 75% of IUGR cases develop during third trimester. Studies on animals (rodents and sheep) as well as humans suggest that insulin-like growth factor-I (IGF-I), under the influence of placental growth hormone (PGH) plays crucial roles in fetal growth regulation during this period. Limited data are available with regard to IGF-I and PGH in placentae of normal and IUGR births. Therefore, in the present study, IGF-I and PGH mRNA expression has been studied in term placentae of normal (n = 10) and IUGR (n = 15) births by in-situ hybridization procedure. Their expression was also studied in first (n = 5) and second (n = 5) trimester placentae obtained from elective termination of normal pregnancies. Both IGF-I and PGH expression were found to be higher in the first and second trimester placentae compared to term placentae in normal pregnancies. However, IUGR term placentae showed increased expression of both IGF-I and PGH mRNA in comparison with normal placentae. Various mechanisms leading to the increased transcription of IGF-I and PGH mRNA in IUGR placenta are discussed. This increased transcription perhaps occurs in response to the reduction in the fetal growth.