FETAL CIRCULATION - fetomaternal circulation

Fetal circulation fetal heart
Circulatory changes at birth
Decribes the maternofetal circulation,

1. FETAL CIRCULATION Dr. M. GOKUL RESHMI Assistant professor OBG Dr. M. GokulReshmi

2. Distinctive features Fetal blood oxygenated by placenta not by lungs. The right ventricular output bypasses the lungs. The fetal heart chambers work in parallel, not in series, which effectively supplies the brain and heart with more highly oxygenated blood than the rest of the body. Dr. M. GokulReshmi

3. Fetal circulation Dr. M. GokulReshmi

4. Dr. M. GokulReshmi

5. Fetal circulation Bl ood in the right ventricle is 15 to 20 percent less saturated with oxygen than blood in the left ventricle. Almost 90 percent of blood exiting the right ventricle is shunted through the ductus arteriosus to the descending aorta. High pulmonary vascular resistance and comparatively lower resistance in the ductus arteriosus and the umbilical–placental vasculature ensure that only about 8 percent of right ventricular output goes to the lungs. Dr. M. GokulReshmi

6. CIRCULATORY CHANGES AT BIRTH After birth, the umbilical vessels, ductus arteriosus, foramen ovale , and ductus venosus normally constrict or collapse. Dr. M. GokulReshmi

7. After Aeration of the lungs at birth Marked increase in the pulmonary blood flow. Dramatic fall in pulmonary vascular resistance. Thinning in the wall of the pulmonary arteries. The more distal portions of the hypogastric arteries undergo atrophy and obliteration within 3 to 4 days after birth. Dr. M. GokulReshmi

8. DUCTUS VENOSUS Sudden fall of blood pressure in the IVC and the right Atrium. The valve of the ductus venosus constricts. The ductus venosus constricts by 10 to 96 hours after birth and is anatomically closed by 2 to 3 weeks. Dr. M. GokulReshmi

9. DUCTUS ARTERIOSUS The action of Bradykinin appears to be dependent on the high Oxygen saturation of the aortic blood. When oxygen tension reaches 50 mmHg in the ductus arteriosus it causes constriction of its smooth muscles. Constriction of ductus arteriosus in the first 24 hours 20%; 48 hours 82% and in 96 hours 100% of the duct is closed. Dr. M. GokulReshmi

10. Fetoplacental Blood Volume Fetoplacental blood volume at term is approximately 125 mL/kg of fetal weight. This is important when assessing the magnitude of fetomaternal Hemorrhage . Dr. M. GokulReshmi

11. Adult derivatives of fetal vascular structures Dr. M. GokulReshmi

12. Thank you... Dr. M. GokulReshmi