Fractionation as in dating

22-Apr-2015 09:37

A positive ONTD screen result means there is an increased risk for the fetus to be affected with an open neural tube defect or other congenital abnormality.

If the patient’s AFP is less than 3.5 multiples of the median (Mo M), if ultrasound dating confirms the gestational age and a singleton pregnancy, and if the gestational age is less than 18 weeks, testing a newly collected sample can be considered.

The earliest EDD calculated by ultrasound should be used for dating purposes.

An ultrasound derived EDD is most accurate when determined in the first trimester. For example, accuracy of an ultrasound EDD is ±7 days in the first trimester and ±10 days in the second trimester.

Furthermore, it’s very unlikely that the typical marker pattern (low AFP, u E3, and h CG) seen in a trisomy 18 positive screen will normalize after recalculation.

For optimal NTD screening, collect samples when the patient is at 16 to 18 weeks gestation. Documentation of the abnormality in the family may enable a more specific risk assessment or indicate whether additional studies should be performed.

A cutoff of 1 in 270, the risk of a 35-year old, is used to determine if a pregnancy is for Down syndrome.

This allows the patient and her partner to better understand her risk of carrying a Down-syndrome affected fetus and to weigh it against the risks and consequences of amniocentesis or cf DNA.

There is no consensus in the literature as to what constitutes a low unconjugated estriol (u E3) level.

Furthermore, it’s very unlikely that the typical marker pattern (low AFP, u E3, and h CG) seen in a trisomy 18 positive screen will normalize after recalculation.

For optimal NTD screening, collect samples when the patient is at 16 to 18 weeks gestation. Documentation of the abnormality in the family may enable a more specific risk assessment or indicate whether additional studies should be performed.

A cutoff of 1 in 270, the risk of a 35-year old, is used to determine if a pregnancy is for Down syndrome.

This allows the patient and her partner to better understand her risk of carrying a Down-syndrome affected fetus and to weigh it against the risks and consequences of amniocentesis or cf DNA.

There is no consensus in the literature as to what constitutes a low unconjugated estriol (u E3) level.

This cutoff is used regardless of the patient’s age, since it’s the historical cutoff for offering diagnostic testing (amniocentesis).