It is known that steroid hormones increase in the blood and urine during pregnancy. For the steroid metabolism in pregnancy there has been proposed a concept of feto-placental-maternal relationship by incubation experiments of fetal adrenals and placenta perfusion experiments and histochemical experiments. More recently with advent of isotopes it has become possible to measure blood steroid hormones so that the steroid metabolism in pregnancy is being elucidated by degrees. During the period from the terminal fetal stage to the newborn stage the adrenal cortex is known to undergo remarkable morphological changes. Namely, it is known that the fetal adrenal weigning ten times that of adult adrenal exists mostly in the fetal zone, which atrophies (shrinks) rapidly after birth and that the activity of 3β-ol-dehydrogenase in the fetal adrenal is extremely weak. In the fetal stage the steroid metabolism is conducted by the maternal-placental relationship, but on delivery this relationship is abruptly severed so that the steroid metabolism is carried out now independently. In view of a great morphological change of the adrenal and steroid metabolism in the fetal stage, the adaptation to the external environments in the newborn stage is truly mystical indeed. An especially interesting problem is just how 3β-ol-dehydrogenase known to possess only a weak activity in the fetal stage would operate in the newborn stage. For the purpose to elucidate how this 3β-ol-dehydrogenase operates on the urinary steroid hormones in newborn stage, the author paid a special attention to the urinary pregene-5en-20α or β-diol (Δ5-pregnenediol to be abbreviated to Δ5 Pd). Δ5-Pd is a saturated form pregnenolone and is a direct metabolite in the urine derived from pregnenolone. Consequently, Δ5Pd, when there occurs a decrease in the activity of 3-β-ol-dehydrogenase or some disturbance so that an excessive precursor flows into the pathway of steroid metabolism and the blood pregenenolone concentration becomes abnormally high, overflows resulting in a large quantity of it in the urine. In other words, when there is an excessive amount of Δ5Pd in the urine it can be considered that there is some abnormality of the steroid metabolism. Therefore, so long as the steroid metabolism in the newbron stage is being conducted smoothly, there would occur no appreciable change of Δ5Pd. With Δ5Fd as it is quite difficult to isolate and colorimetory, most of attempts of isolation-coloration procedures are done with Δ-5-3β-ol-steroid as a whole. The author devised a new method of isolation-coloration of Δ5Pd for the purpose to elucidate the adaptation of newborn to external environments from urinary steroid hormones, and carried out the measurements of Δ5Pd with lapse of time using urine collected from normal newborn babies. The results are summaried as follows. 1. By means of florisil column chromatography and impregnant TLC, it was possible to isolate Δ5Pd into pregnenolone, 17-OH-pregnenolone, 17-OH-progesteron and DHA, with allmost the same polarity. 2. By the new coloration method with Δ5Pd the color sensitivity as high as 1.5 to 2 times that of Oertel and Eik-Nes was attained. 3. As for the identification of Δ5Pd, it has been confirmed by the spots with the same Rf in the impregnant TLC, and in gas liquid chromatography using two kinds of filler by the same R. R. T., and by the coincidence of serial absorption curves in the coloration method. 4. As regards time-lapse (diurnal) changes of Δ5Pd, looking at the average values, there could be seen not so much change after birth, decreasing gradually. Looking at separate individuals, they could be divided into three groups: postnatal decreasing group, postnatal ascending group, and no change group. 5. The steroid metabolism of newborns has been indicated to be being carried on smoothly from the low values of Δ5Pd. 6. It has been demonstrated that the adaptation of newborns to external environments is completed by 5.7th (5th to 7th) postnatal day.