Fetal heart rate is a relative marker for fetal aneuploidy . It is also related to some chromosomal abnormalities.
At 5 weeks the embyo’s heart rate is around 110 bpm and increases up to 170 bpm at 9 weeks . It decreases to 150 bpm at 14 weeks.
Turner’s syndrome and trisomy 13 are associated with fetal tachycardia , trisomy 18 and triploidy with bradycardia and in trisomy 21 there is a mild increase in the fetal heart rate.