Intracardiac pressures in the human fetus

OBJECTIVE—To obtain normal values for intracardiac pressures in the human
fetus.
DESIGN—Intracardiac pressures were measured directly in the four chambers of the human fetal heart during clinically indicated invasive obstetric procedures.
SETTING—Department of fetal medicine in a tertiary referral centre.
PATIENTS—39 fetuses between 16 and 29 weeks of gestation.
RESULTS—The ventricular waveforms obtained were similar to those found in postnatal life. There was an increase in ventricular systolic and end diastolic pressures with advancing gestation. There was no difference between left and right ventricular pressures. Atrial pressures were equal and remained constant in the gestational age range studied.
CONCLUSIONS—Fetal cardiovascular pressure measurements in the normal fetus assist in understanding the fetal circulation, and provide a basis for the assessment of cases of congenital heart disease that may be amenable to intrauterine treatment.


Keywords: fetus; ventricular pressure; congenital heart disease     

Intrahepatic lymphatics in the human fetus

Graphic reconstruction of dilated intrahepatic lymphatics in a 36 week old fetus displayed an anastomosing network of channels with intraluminal valves. Examination of the liver in 42 fetuses between the gestational age of 15 to 40 weeks showed that lymph vessels were visible as early as the 15th week. The detection of intrahepatic lymphatics was not related to the weight of the liver, the underlying cause of death, gender, or congenital anomalies.     

Live three-dimensional echocardiography of the human fetus

The purpose of this study was to investigate the feasibility of using a new three-dimensional ultrasound system to perform fetal echocardiographic examination in real time. The device consisted of a Philips Sonos 7500 (Andover, MA) ultrasound system and a 4 MHz, 4X matrix transducer. The study was approved by the Institutional Review Board and was performed with the informed consent of the mother. The study population consisted of 12 singleton fetuses with gestational ages of 16-37 weeks. Of these, ten fetuses had normal cardiac anatomy, one had complete atrioventricular septal defect, and the other a thickened tricuspid valve. The system allowed comprehensive visualization of fetal cardiac anatomy and color Doppler flow unattainable by two-dimensional approaches. This preliminary investigation suggests that live three-dimensional fetal echocardiography could be a significant tool for prenatal diagnosis and assessment of congenital heart disease in the human fetus.     

Ontogenesis of pituitary prolactin in the human fetus

To study the ontogenesis of PRL synthesis and secretion in the human fetus, PRL mRNA was measured in 12 pituitaries from fetuses of 16-27 weeks of gestation by hybridization of cytosol RNA with 125I-labeled single stranded complementary DNA (cDNA). Pituitary PRL content and serum PRL concentration were assessed by RIA. Pituitary weight increased with fetal age, ranging from 12 mg at 16 weeks of gestation to 41 mg at 27 weeks. The increased weight was due to an increase in cell number. PRL mRNA content did not change during weeks 16-20 of gestation. However, it increased rapidly after 21 weeks, reaching 11.5 times the 16-20 week value at 27 weeks. Pituitary PRL content was constant at a low level until 21 weeks, but thereafter it increased markedly. The increase was greater than that in PRL mRNA, and therefore, the PRL to PRL mRNA ratio was 10-fold greater at 27 weeks of gestation. Serum PRL concentrations also gradually increased after 21 weeks of gestation. These results indicate that marked increases in fetal pituitary PRL synthesis and release occur after 21 weeks of gestation.     

Growth of the great vessels in the normal human fetus and in the fetus with cardiac defects

BACKGROUND. There is a paucity of quantitative anatomic data regarding human great vessel development that could be useful as a reference for fetal echocardiographers who must distinguish abnormal from normal cardiac development at early stages. METHODS AND RESULTS. To determine normal growth patterns, we plotted the diameters of the aortic and pulmonary valves, ductus arteriosus, aortic isthmus, and descending aorta in 274 autopsy specimens from nonselected spontaneous abortuses of normal karyotype. There was a linear increase in the diameters of these structures within the developmental period studied (10-26 weeks). A relative narrowing of the aorta at the isthmus compared with the aortic valve and descending aorta probably indicates that the majority of fetal left heart output goes to the developing heart and brain. In contrast to previous studies of late gestation and neonatal animals, however, we found that the diameter of the aortic isthmus was larger than that of the ductus arteriosus, suggesting substantial isthmic blood flow in these midtrimester fetuses. Among nineteen other hearts with diverse defects, both of two hearts with a narrow isthmus had an enlarged ductus arteriosus and one heart with pulmonary atresia/intact septum had a narrow ductus and increased aortic valve diameter. CONCLUSIONS. During midgestation, the normal heart may have substantial aortic isthmic blood flow that diminishes due to rerouting in late gestation when increased requirements of the fetal brain and other organs prevail. Although fetal shunts may explain some vessel abnormalities, the majority of cardiac defects in this study were not associated with abnormal growth of the great vessels within this developmental age range.     

M-mode echocardiography in the developing human fetus.

The M-mode echocardiogram can be obtained in the developing human fetus from around the 16th week of gestation until term. Errors in interpretation of the M-mode echocardiogram can be avoided by concurrent two dimensional fetal cardiac examination. The pattern of motion of the mitral, tricuspid, aortic, and pulmonary valves and ventricular wall motion can be studied. Motion of the foramen ovale flap, which is characteristic in fetal life, can also be observed. Using the M-mode tracing, measurement data for six variables were made and growth charts constructed. The variables recorded were septal and left ventricular wall thickness, right and left ventricular internal dimension in diastole, aortic root dimension, and left atrial internal dimension. The measurements were made in normal pregnancies where the fetal heart was structurally normal. Confidence limits for each measurement were derived for gestational ages between 16 and 39 weeks.