The parents and the doctors indeed want to know as early as possible about the possibility of genetic anomalies. The earliest window available for getting such information is between 10 to 14 weeks (or 13 weeks + 6 days to be more precise) through the double market test and NT scan.
The NT Scan or Ultrasound Scan
The ‘NT Scan’ as it is popularly known as is an ultrasound scan performed in the first trimester (between 11 to 14 weeks) to measure Nuchal Translucency (NT) and nasal bone (NB). This gives important information about the babies’ health and progress of the pregnancy. The NT Scan is not like a regular ultrasound scan offered by any ultrasound center. It is a specialized scan which is performed by experienced ultrasonologist, fetal medicine specialist or gynecologist with experience in the measurement of nuchal, crown-rump length (CRL) and other ultrasound markers. The ultrasound scan readings should be combined with the biochemical marker to arrive at a more definitive risk assessment.
Double Marker – Two Biochemical Parameters
It has been found that there is a strong correlation between certain biochemical parameters and the fetal abnormalities. Two such biochemical parameters which are relevant in the first trimester are Free Beta-human chorionic gonadotropin (Free B-HCG) and ‘Pregnancy-Associated Plasma Protein (PAAP-A).
By combining the result of the NT Scan and the two biochemical parameters (Dual Maker or Double Marker) into a sophisticated risk calculation algorithm or software, we can provide a reliable indication for the risks of Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18) and Patau Syndromes (Trisomy 13). The First Trimester Screening presents significant advantages over other tests because of higher detection rates (90-95% with 5% false positive rates), and the availability of information at an early stage of pregnancy. ~ (Reference: Fetal Medicine Foundation).
Pre-eclampsia Screening – Two Biochemical Parameters
Pre-eclampsia is a frequent pregnancy disorder (incidence of 2-8%) affecting more than 1 million women worldwide annually. It is caused by the inadequate circulation of blood between placenta and uterus resulting in the decresed supply of oxygen and nutrients to the fetus. It can lead to Hemolysis, Elevated Liver enzymes, and Low Platelets also know as the HELLP syndrome. HELLP syndrome and eclampsia account for more than 50,000 maternal deaths per year. Early identification of high-risk women for pre-eclampsia can enable the clinician or gynecologist to take preventive measure and intensified monitoring of the pregnancy. Combing Serum markers of PLGF and PAPP-A measurements along with Mean Arterial Pressure (MAP) and Uterine Artery Pulsatility Index (UAPI) gives a very good detection rate of >905 with a 5% false-positive rate for Pre-eclampsia. Hence it is advisable to combine the Double Marker Test and the Pre-eclampsia screening for getting a more comprehensive assessment of genetic risks and the pregnancy outcomes.
Learn More about Pre-eclampsia Screening and Diagnosis
