How to use the heart monitor?

Cardiac care is used cardiac monitor heart rate curve and contractions down pressure waveform for clinical analysis of graphics, is a major testing methods in evaluating fetal condition correctly.Beauty international heart monitor by microwave technology, no harm to children.Many parents are at home now for cardiac monitoring, so how to use the heart monitor?
General can hear heart when 12 weeks of pregnancy, but this time the cardiac sound is very light, with a heart monitor to hear, with a heart the receiver at the time of 18 weeks before he can hear heart.Pregnant women for 15 to 28 weeks of pregnancy, 3 times a day, every time 1 minute is safe.For pregnant women after the 28th week of gestation, fetal differentiation completely, can be extended custody of time and frequency.For high-risk pregnant women at 35 weeks later, should be in the hospital with a heart monitor continuous heart guardianship, if necessary, can continue to care for a long time.