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Researchers report the first known study that analyzed how the fetal heart fills after each contraction beginning at the 16th week of pregnancy and continuing to the age of 12 months after birth. Doppler ultrasound was used to determine filling patterns at 16 weeks, every 4-6 weeks thereafter until birth, and at the ages of 1 and 2 days, 6 weeks, 6 months and one year. Results show that the fetal heart has filling properties similar to adults with heart disease. The heart was stiffer and the right side of the heart was dominant rather than the left.

Chronically inadequate oxygenation of the fetal heart appears to induce ventricular enlargement and increased blood vessel development. Researchers deprived fetal sheep of oxygen by diluting their blood. Oxygen-deprived, or hypoxic, hearts were bigger, had larger capillaries, and denser capillary networks than the hearts of fetuses normally oxygenated. Vascular endothelial growth factor and hypoxia-inducible factor 1 alpha protein levels were higher in the ventricles of hearts deprived of oxygen. Oxygen deprivation may cause compensatory changes in the fetal heart.

It appears that the human heart adapts to the transition to life outside the womb and during the first year of life by increasing the size of the ventricles. Researchers used echocardiography to periodically assess heart anatomy and function in 52 normal fetuses beginning as early as 16 weeks gestation and ending at 12 months old. Heart rate decreased during pregnancy and after birth without a change in ventricular ejection fraction and without a change in contractility. This suggests that the ventricles adapt by increasing in size.

Atrial natriuretic factor (ANF) levels in the atrial chambers of the heart rise with increasing gestation in fetal sheep. ANF acts as a diuretic and helps maintain low blood pressure. The hearts of 51 fetal sheep at different gestational ages and five newborn lambs were dissected. Fetal heart weight increased from 70 days' gestation until term at 147 days. ANF levels were higher in the atria than in the ventricles. Atrial ANF levels were lowest at 70 days' gestation and peaked at 140 days. ANF levels in the newborn were lower than those at 140 days' gestation. Ventricular ANF levels remained low between 70 and 130 days with a peak at 100 days' gestation. At 140 days ventricular ANF levels were similar to those found in newborns. Atrial ANF levels were on average 20 times greater than ventricular levels in both fetuses and newborns. ANF messenger ribonucleic acid signals were strong in the atria at 110 days' gestation, though they were low at 90 days.

A simple, low cost and non-invasive personal computer based system for the acquisition of passive acoustic signal is developed. The system hardware consists of a phonocardiographic sensor, a heart sound signal preprocessing circuit, and a personal computer, while the system software consists of a fetal heart sound acquisition program, a signal analysis program, and a data storage function block. The acquisition program is used to switch on or off of the hardware equipments for initializing the sampling rate, the number of acquisition channels and other relevant setups. The collected data in its original form is saved through storage function block for the purpose of further subsequent analysis. In this study, an attempt has been made to develop a phonocardiography based data acquisition system for non-invasive fetal monitoring applications with many advantages like long term home monitoring and high performance to cost ratio. The system was justified by recording the fetal heart sound from 21 subjects with different gestational period. The result shows that the overall accuracy of the system is 98.02%. The developed system can be efficiently used by a fetal heart sound monitoring system for long-term fetal heart rate monitoring in a fully passive manner. Keywords: Electronic Fetal Monitoring | Data Acquisition | Phonocardiography | Noise | Heart Rate, Introduction Electronic fetal monitoring (EFM) is a method for examining the condition of an unborn in the uterus by noting any unusual changes in its heart rate (1). The EFM [...]