[Fetal functional atrioventricular blocks in pregnancies at risk]

Because antepartal and subpartal CTG monitoring is now widespread, fetal cardiac arrhythmias are being diagnosed ever more frequently. In a high-risk group of 148 pregnancies with placental insufficiency and preterm births, 14 CTGs manifested a rigid rectangular pattern, with alternating normal-frequency and slightly bradycardial cycles. The change in frequency occurred suddenly. All the children of the high-risk group were delivered by cesarean section and weighed less than 2500 g at birth. There is no description in the literature of similar CTG curves with sligthly bradycardial phases. However, there are some descriptions of cases of fetal AV blocks with severe bradycardias. These frequently occur in combination with fetal cardiac abnormalities and collagenoses of the mother. In the present authors' group these underlying conditions were not diagnosed. The fixed numerical ratio of the output frequency to slight bradycardia in the CTGs described here supports the tentative diagnosis of an atrioventricular conduction disorder, with relatively high conduction from the atrium to the ventricle. Since the arrhythmias did not continue in the newborns post partum it may be assumed that they were functional events. Birthweight, Apgar score, and the placental weight of the 14 births with the rectangular CTG curve described were lower than in the control group, i.e., the other 134 births. The CTG patterns described appear to have been caused by a chronic supply deficiency, resulting in functional AV conduction disorders. This CTG course should therefore be reason enough for intensive fetal monitoring.