Evaluation of fetal heart rate variation during amniocentesis: correlation with fetal karyotype

We monitored the fetal heart rate (FHR) during amniocentesis in fetuses at 16-18 weeks of gestation and investigated whether an abnormal FHR is associated with chromosomal abnormalities.

This prospective study involves 807 women at 16-18 weeks of gestation who underwent genetic amniocentesis. The FHR, expressed as beats for minute, is recorded before (FHR1), immediately after (FHR2) and 60 min after (FHR3) the invasive procedure. Structural malformations detected by ultrasound and multiple pregnancy are excluded from the study.

Chromosomal abnormalities have been diagnosed in 27 fetuses. A mean FHR decrease after amniocentesis has been observed in normal and in abnormal fetuses. The mean variation during amniocentesis is significant in both groups (P < 0.01). The comparison between the mean FHR of the two groups shows no differences in FHR1 and FHR2 (P > 0.05) but a significant difference in FHR3 (P < 0.05).

The FHR decreases after amniocentesis; the decrease is larger in chromosomally abnormal fetuses than in normal fetuses. This difference in heart rate reaction to amniocentesis might be due to cardiac defects or developmental delay associated with the abnormal karyotype.