Cheaper at-home fetal heart monitors may not be medical-grade. (CBC)

Expectant parents should not rely on fetal heart monitors at home to give them an accurate picture of their baby's health, a doctor says.

"If not used properly these devices can provide false reassurance," Dr. Abhijoy Chakladar of Princess Royal Hospital in West Sussex, England, wrote in a commentary this week in the British Medical Journal.

Chakladar reported on the case of a 34-year-old woman who was 38 weeks pregnant.

One day, she noticed her baby was moving less than usual but reassured herself at home by listening to a fetal heart monitor. A few days later, however, the woman was unable to hear the baby's heartbeat so went to the hospital. An urgent ultrasound showed a death in the womb.

Doctors believe the woman had been hearing her own heartbeat or placental blood flow on the home monitor.

Chakladar said the tragic death may have been unavoidable, but use of a fetal heart monitor certainly led the woman to delay going to hospital.

Without training, the sounds heard on the home devices could easily be misinterpreted, he said. Home monitoring devices provide only a snapshot of the heart rate and "provide no indication of other important prognostic features," he said.

Medical professionals such as midwives and obstetricians provide context by taking histories and observing expectant mothers before making a diagnosis, Chakladar said.

At-home fetal heart monitors are often sold on the internet and may not be medical-grade, Rebecca Coombes, associate editor of the British Medical Journal, said in an accompanying editorial.

Chakladar called on health-care professionals to "educate expectant mothers about the limitations and consequences of untrained use of the devices."