Real-time ultrasound studies of fetal activity in the third trimester
This thesis consists of four studies. All studies involved the use of a real-time ultrasound scanner. The real-time picture was displayed on a television screen and a manual punch attached to an electronic timer used to record each breath and trunk movement of the fetus. This data was stored on punched tape and analysed by computer. Study I was designed to investigate the various patterns of fetal activity in the third trimester in normal pregnancy,and to investigate some of the factors that might. influence this activity. Twenty-four hour studies were followed by further investigations during the day. Both fetal respiratory movement and fetal trunk movement were found to vary consider ably at any time of day. They were influenced by time of day,meals, gestational age, glucose, and catacholamine levels. The normal fetus was however usually very active and periods of complete inactivity rarely lasted longer than ten minutes. Another way of expressing this is that "Total Fetal Activity" (TFA) (Fetal respiratory plus trunk movement) was rarely below 10% in any one recording period of thirty minutes or more. It was thought that this fact might be useful clinically.Study 2 was designed to investigate the hypothesis (widely accepted at the time) that maternal appreciation of fetal movement was effective in detecting more than 80% of fetal movement. It was found that maternal appreciation of fetal movement was extremely variable, ranging from 0-90% detection. It was felt that the study of fetal movement with ultrasound gave significantly more information than maternal sensation.Growth-retarded fetuses (Study3) were then studied over 24 hoursand during the day. Some growth-retarded fetuses had grossly diminished fetal activity. Levels of TFA below 10% correlated well with abnormal fetal heart traces.Study 4 investigated the incidence of fetal respiratory and trunk movements in the fetuses of mothers with diabetes mellitus. The incidence of respiratory movement was much higher and this was thought to be directly related to maternal blood glucose levels.