Reliability of ultrasound dating
In spite of this ongoing debate as to the feasibility and efficacy of routine ultrasound evaluation in pregnancy, one thing remains clear: ultrasound examination of the fetus provides the most precise assessment of gestational age, especially in the first trimester.
This variance has evolved from years of study by several esteemed researchers who have sought the most accurate measurement parameters in determining gestational age and normal patterns of fetal growth.
The EDD from the early dating scan is used - if the last menstrual period is not known or is unreliable, or the dating scan differs from the last menstrual period dating by more than 5 days.
As the baby gets bigger, it starts to express its individual growth potential.
Sometimes a trans-vaginal examination shows that your pregnancy is less advanced than expected.
They further concluded that the costs associated with routine screening were too prohibitive to justify its use in the absence of clear medical indications.For example, when the margin of error is reported as a percent of the total, it is calculated against the number of days gestation verses the number of weeks.In other words, an 8% margin of error at 8 weeks' (or 56 days') gestation calculates to ± 5 days; at 18 weeks' (126 days') gestation, this represents a range of ± 10.08 days; lastly, at 28 weeks' (196 days') gestation, the margin of error continues to widen to ± 15.68 days.states that obstetricians are under no obligation to perform routine ultrasounds in low-risk women; however, it is reasonable to honor a patient's request for one.This is an interesting sidebar that provides some latitude in an otherwise firm stance echoing the RADIUS trial findings.