Device May Aid Pregnancy Monitoring

By Marcia Wood
June 19, 1998

An expectant mother's chances of delivering a healthy, normal-weight baby may increase in the future. That's thanks to a promising new technique for monitoring the pregnancy.

Called bioimpedance spectroscopy, the technique may allow fast, convenient and painless measurements of water-weight gains during pregnancy. Scientists with the Agricultural Research Service, the University of California at Berkeley, and Xitron Technologies, Inc., San Diego, Calif., showed that bioimpedance measurements correlate significantly with infant birth weight. The researchers measured water-weight gain of 10 women before pregnancy, at intervals throughout pregnancy, and after delivery.

With further study, bioimpedance spectroscopy may augment ultrasound monitoring, according to ARS research physiologist Marta D. Van Loan at the Western Human Nutrition Research Center, San Francisco. Van Loan led the bioimpedance monitoring.

Low-birth weight babies--those weighing less than five and one-half pounds at birth--have an even greater risk of early health complications than premature babies. An expectant mother who does not eat properly, exercises too vigorously, takes diuretics or abuses drugs, for example, may deliver an underweight infant.

Physicians have known for more than four decades that moderate water accumulation during pregnancy is a strong indicator of proper fetal growth. The ARS-led investigation, however, was likely the first to show that bioimpedance spectroscopy may offer an safe, accurate and inexpensive way for physicians to detect subnormal water-weight gains in time to help their patients take corrective action.

Bioimpedance measurements take less than two minutes to perform. They involve sending a harmless current between electrodes positioned on the hand and foot. A personal computer linked to the bioimpedance spectrometer processes these measurements. It then prints out an estimate of the patient's water load, called "total body water."

Scientific contact: Marta D. Van Loan, USDA-ARS Western Human Nutrition Research Center, P.O. Box 29997, Presidio of San Francisco, CA 94129, phone (415) 556-5729, fax (415) 556-1432, mvanloan@whnrc.usda.gov.