In the first trimester ultrasound (sonography) may be used to confirm the presence of an intrauterine pregnancy or ectopic pregnancy. Ultrasound can estimate gestational age, the number of embryos and confirm embryonic life. It is used to help determine the cause of vaginal bleeding, evaluate pelvic masses or detect uterine abnormalities.
Scanning in the first trimester is to be performed transvaginally. Theexception tothis, is if the patient is undergoing genetic screening. In this case, the patientshould have a full bladder and the exam is performed transabdominally.
No preparation is required to a first trimester transvaginal sonogram. However ifthe patient is coming for genetic screening, the patient should have a full bladder.
In the second or third trimester, ultrasound may be used to estimate the gestationalage, evaluate fetal growth and estimate fetal weight. Ultrasound can determinethe position of the fetus, evaluate fetal anatomy and viability. Ultrasound can alsoassess the location of the placenta, its appearance and relationship to the cervix.
Scanning in the second and third trimester is performed using a transabdominalapproach, therefore the patient must have with a partially filled bladder. Infrequently, the cervix cannot be adequately visualized, a transvaginal sonogram is performed after the patient has emptied her bladder.
The patient should arrive with a full bladder. She should drink approximately 8ounces of fluid about 1 hour before her appointment time.