[Exercise test and differential diagnosis of fetal arrhythmia]

The cases here reported show in the first place that external fetal ECG is useful to detect fetal distress and should therefore be included as a prenatal control from the second trimester of pregnancy on, specially in cases where there is a past history of fetal death of unknown origin, or a family history of congenital heart defects. A fetal tolerance test to exercise should also be done in those cases with a past history of fetal death, distress or whenever chronic fetal distress may be suspected to take place because of the presence of maternal pathology (endocrine, cardiovascular, or infectious diseases, etc.). Fetal tolerance test to uterine contractions should also be done whenever possible to evaluate the tolerance of these fetuses to uterine contractility during labor. More studies are needed to establish standard guides of this method for the practical obstetrical management of products of high risk pregnancies.