between days 16 and 20 of gestation , enzyme activities towards the substrates 2-aminophenol , 2-aminobenzoate , 4-nitrophenol , 1-naphthol , 4-methylumbelliferone and 5-hydroxytryptamine ( the 'late foetal ' group ) surge to reach adult values , while activities towards bilirubin , testosterone , beta-oestradiol , morphine , phenolphthalein , and chloramphenicol ( the 'neonatal ' group ) remain negligible or at less than 10 % of adult values .
C0032961
gestation
C0014912
oestradiol