Meconium/analysis; Steroids/analysis; Sterols/analysis; 17-Hydroxycorticosteroids/analysis; 17-Ketosteroids/analysis; 17-alpha-Hydroxypregnenolone/analysis; Androstanes/analysis; Androsterone/analysis; Bile/metabolism; Chromatography; Chromatography, Gas; Chromatography, Paper; Chromatography, Thin Layer; Dehydroepiandrosterone/analysis; Female; Fetus/metabolism; Glucuronates/analysis; Humans; Infant, Newborn; Intestine, Small/physiology; Maternal-Fetal Exchange; Placenta/metabolism; Pregnancy; Pregnanes/analysis; Pregnenolone/analysis; Spectrum Analysis; Testosterone/analysis