Fetal cardiac output and its distribution to the placenta and brain at 11-20 weeks of gestation
Year: 2009
Type: dissertation
Study design: Observational Study
Abstract: Objective: \nTo study some aspects of fetal heart structure and function using ultrasonography at 11-20\nweeks of gestation with an emphasis on the distribution of cardiac output to the placenta and\nupper body including brain.\n \nMethods:\nIn a cross-sectional study of unselected pregnant population, the structure of the fetal heart\nwas studied using transvaginal ultrasonography and feasibility of obtaining standard\nechocardiographic views and measuring different structures was evaluated in 584 fetuses at\n11+0-13+6 weeks of gestation. Reference ranges were established for the heart/ thorax\ncircumference ratio, ventricular size and the diameters of the aorta and main pulmonary artery\nat the respective semilunar valve levels.\nThe fetal cardiac function was studied in a prospective longitudinal study of 143\npregnant women from an unselected population who were serially examined three times\nduring 11-20 weeks of gestation. Blood flow velocities and diameters of the main pulmonary\nartery, aorta, aortic isthmus and umbilical vein were measured using pulsed-wave Doppler\nand B-mode ultrasonography, respectively and the reference ranges were constructed. The\nvolume blood flow (Q) was calculated as a product of mean velocity and cross-sectional area\nof the vessel. Reference intervals were established for the umbilical vein (Quv) and aortic\nisthmus (Qai) volume blood flows and the left (LVCO), right (RVCO) and combined (CCO)\nventricular cardiac outputs. The fraction of CCO distributed to the placenta was calculated as:\nQuv/CCO*100 and the fraction of CCO distributed to the upper body and brain was calculated\nas: (LVCO – Qai)/CCO*100.\n \nResults: \nIt was possible to study the fetal heart anatomy by obtaining standard echocardiograhic views\nusing transvaginal ultrasonograpy in a majority of cases in the late first trimester. The cardiac\nventricles and their outflow tracts showed a linear growth with advancing gestational age\nduring 11-14 weeks of gestation.\nThe CCO increased 1.9-fold from 11 to 20 weeks of gestation and the placental\nvolume blood flow almost tripled during the same period. The fraction of CCO diverted to the\nplacenta increased from 14% at 11 weeks to 21% at 20 weeks.\nAortic isthmus had a positive forward flow during the whole cardiac cycle\nduring 11-20 weeks of gestation. Aortic isthmus blood flow velocities as well as the diameter increased with advancing gestation, resulting in a significant increase in Qai from 1.9 to 40.5\nml/min during 11-20 weeks. However, the fraction of CCO directed to the upper body\nincluding brain remained relatively stable (approximately 13%) during this gestational period.\n \nConclusion: \nIt appears feasible to study fetal heart anatomy in late first trimester using transvaginal\nechocardiography and to confirm normality. We have established references ranges for the\nevaluation of some cardiac structures at 11-14 weeks of gestation and for the serial\nmeasurement of Quv, Qai and cardiac ventricular outputs at 11-20 weeks of gestation. Placental\nvolume blood flow and the fraction of CCO distributed to the placenta increases substantially\nduring 11-20 weeks of gestation reflecting faster placental growth relative to fetal growth and\nestablishment of low resistance circulation during the first half of pregnancy. The fraction of\ncardiac output directed to the upper body and brain is relatively small but fairly constant\nduring 11-20 weeks of gestation.
Author: Tommi Vimpeli
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2109893092