Parents should not count on three types of electronic devices designed to alert them when they’ve forgotten a baby strapped in a car seat, federal officials said Monday.

  The performance of the devices – one that relies on a chest buckle sensor and two that use seat pads – is too inconsistent, the National Highway Traffic Safety Administration said.

  “These sense the presence of a child; they just don’t do it reliably enough,” said Kristy Arbogast, a researcher at the Children’s Hospital of Philadelphia who tested the devices for the federal agency.

 “While these devices are very well intended and we do appreciate the manufacturers and inventors, we have found a number of limitations in these devices,” NHTSA Administrator David Strickland said. “We don’t think they can be used as the only countermeasure to make sure that you don’t forget your child behind in a car.”

  The three devices are the Suddenly Safe Pressure Pad, the ChildMinder Smart Clip System and the ChildMinder Smart Pad. There was no immediate response from the three manufacturers.

   The NHTSA report said that, in some cases, spilled liquids caused malfunctions, cellphone use interfered with device signals, devices turned off and on during travel and an improperly positioned child caused seat pads to malfunction.

   “In sum, the devices require considerable effort from the parent/caregiver to ensure smooth operation,” the report said.

   Arbogast said, however, that the designs of the three devices are conceptually sound.

   “Speaking with the manufacturers of these technologies, we know that many refinements already are underway,” she said.

  The report did not evaluate electronic devices that have come on the market since the study began. Nor did it test the effectiveness of non-electronic reminders such as wrist bands and similar items.

 Release of the report was timed to coincide with the hottest time of the year in a bid to draw attention to the deaths of infants and toddlers left behind in cars, where temperatures can soar past 130 degrees.

 NHTSA said heatstroke is the leading cause of vehicle-related deaths not involving crashes for children under 14. There were 33 child deaths due to hyperthermia in vehicles last year, and at least 49 deaths in 2010. They have been 527 heatstroke-related child fatalities reported since 1998.

  Strickland said there was no evidence that tied distraction from the use of a mobile device to cases in which a child was forgotten in a car.