HTR5A and fetal growth restriction: Raised circulating FFT and increases in tryptophan uptake by serotonergic neurons, the activity of tryptophan-5-hydroxylase and synthesis of 5-HT have also been reported in intrauterine growth-restricted (IUGR) rat pups and infants (Kalyanasundaram, 1976; Hernandez et al., 1989; Manjarrez et al., 1996, , 1998).