Timed 12-hour specimens in outpatient estriol monitoring.

Use of maternal urinary estriol excretion to monitor fetal status is often hampered by the difficulties of obtaining 24-hour specimens. Evidence is presented that timed, 12-hour overnight specimens may be substituted for the 24-hour specimens in certain patient groups. A simple non-refrigerated transport system which facilitates outpatient estriol monitoring is also described.