[Instrumentation of birth weight in obstetric facilities]

An investigation on measurement of birth weight in facilities was made in the northern part of Fukuoka Prefecture from March 1989 to January 1991. The purpose of the investigation was to clarify the reliability of birth weight data in obstetric facilities. The author interviewed the manager of each facility. The data of 112 cases were analyzed. The following results were obtained: 1) Nurses and midwives measured birth weights in many facilities, but doctors rarely did. Birth weights were obtained within an hour after birth in almost all facilities. Tare and zero-adjustment were frequently checked in many facilities, but horizontal-adjustment was not checked in about a half of the facilities. 2) The types of scales were digital scales (48.2%), dial scales (31.3%), table-top platform scales (10.7%) and bathroom scales (9.8%). It was estimated that 70.6% of the all birth weights in these facilities were obtained with digital scales. The renewals of scales in the past 5 years has resulted in the widespread use of digital scales in facilities. 3) The accuracy and precision of each scale were examined with weights of 3000g. Digital scales were superior to the other types of scales in both accuracy and precision. The legal periodical inspection for scales improved accuracy. Procedures for measuring birth weight are not generalized among and within facilities. Digital scales have many merits for handling and reading. The spread of digital scales in facilities may decrease the degree of many kinds of errors in measurement, especially rounding errors, and improve the reliability of the data in the area.