Dating viability sonogram
A gestational sac can be reliably seen on transvaginal ultrasound by 5 weeks' gestational age (approximately 3 weeks after ovulation).The embryo should be seen by the time the gestational sac measures 20 mm, about five-and-a-half weeks.A short cervix preterm is undesirable: At 24 weeks' gestation a cervix length of less than 25 mm defines a risk group for preterm birth, further, the shorter the cervix the greater the risk.
Ultrasound scans offer an alternative method of estimating gestational age.
Some resources indicate that there are clear reasons for this and that such scans are also clearly beneficial because ultrasound enables clear clinical advantages for assessing the developing fetus in terms of morphology, bone shape, skeletal features, fetal heart function, volume evaluation, fetal lung maturity, Second-trimester ultrasound screening for aneuploi- dies is based on looking for soft markers and some predefined structural abnormalities.
Soft markers are variations from normal anatomy, which are more common in aneuploid fetuses compared to euploid ones.
This includes checking the status of the limbs and vital organs, as well as (sometimes) specific tests for abnormalities.
Some abnormalities detected by ultrasound can be addressed by medical treatment in utero or by perinatal care, though indications of other abnormalities can lead to a decision regarding abortion.
There is no difference, however, in perinatal death or poor outcomes for babies.