Objective: The purpose of this study was to evaluate the role of a slow embryonic heart rate in embryos before 7 weeks' gestation as a marker in screening for chromosomal abnormalities.
Methods: Fifty-seven embryos before 7 weeks' gestation with slow heart rates were compared with 1156 embryos of the same gestational period with normal heart rates. Embryos that showed an increased risk of chromosomal abnormalities in the screening blood tests underwent invasive analysis for abnormal karyotype detection.
Results: The rates of first-trimester death were 15.8% for pregnancies with slow embryonic heart rates (9 of 57) and 2.5% for those with normal heart rates (29 of 1156). Because of the increased risk of chromosomal abnormalities, amniocentesis was performed on 6 with slow embryonic heart rates and 61 with normal embryonic heart rates. After karyotype analysis, there were 2 fetuses with trisomy 21 in each group, which represented significantly higher percentage of embryos with trisomy 21 in the slow-heart rate group compared with the normal-heart rate group (P < .05).
Conclusions: When a slow embryonic heart rate is detected before 7 weeks' gestation, there is a higher likelihood of chromosomal abnormalities.