In the name of god First Trimester Screening Dr.M.Moradi

First Trimester Screening A method to identify women at risk for having an aneuploid fetus from the general population Also can identify other birth defects such as congenital heart defects and diaphragmatic hernia Performed during weeks gestation Patient Preferences and earlier diagnosis/ reassurance

All patients have a 2% to 3% risk of birth defects, regardless of their prior history, family history, maternal age, or lifestyle. Chromosome abnormalities account for approximately 10% of birth defects.

A detailed fetal anatomic survey performed at 18 to 22 weeks remains the primary means for detecting the majority of serious ‘‘structural’’ birth defects. first-trimester screening at 11 to 14 weeks has developed into the initial screening test for many patients.

The primary advantage of first trimester screening is earlier diagnosis of abnormalities (or early reassurance of the anxious patient), with the option of an earlier and safer pregnancy termination.

Advantages of 1st Trimester Screening Information earlier, more options Reduce number of invasive procedures May identify other severe anomalies (or risk for) at time of scan and increased risk of adverse pregnancy outcome—referral for 2 nd Δ evals. Good time to date pregnancy accurately NT good for multiple gestation

First Trimester Screening GOALS of this screen: To increase sensitivity, decrease false-positive rates To decrease number of “unnecessary” invasive prenatal diagnosis tests. NOT to increase number of elective abortions. U/S measurements (NT) and free B-hCG, PAPP-A

Use of the guidelines proposed by the Fetal Medicine Foundation have resulted in a high consistency in results

Nuchal translusency

History ◦ Dr.langdon Down 1866 ◦ 1980s ◦ 1992…..prof Nicolaid…. Normal range? Mechanism? Normal Karyotype with increased NT

The mechanism for increased NT may vary with the underlying condition. The most likely causes include heart strain or failure and abnormalities of lymphatic drainage. Evidence for heart strain includes the finding of increased levels of atrial and brain natriuretic peptide mRNA in fetal hearts among trisomic fetuses

Nuchal Translucency Measurements must be performed by certified individual!

True sagital Position Caliper Separation of amnion magnification

The normal range for NT measurements is gestational age dependent. the median NT increases from 1.3 mm at a crown-rump length (CRL) of 38 mm to 1.9 mm at a CRL of 84 mm. The 95th percentile increases from 2.2 mm at a crown rump length of 38 mm to 2.8 mm at a CRL of 84 mm.

The ability to measure NT and obtain reproduciblen results improves with training; good results are achieved after 80 and 100 scans for the transabdominal and the transvaginal routes, respectively

screening Basic ◦ NT ◦ BIOCHEMISTRY Advanced

The two most effective maternal serum markers currently used in the first trimester are pregnancy- associated plasma protein A (PAPPA) and free B-human chorionic gonadotrophin (B-hCG). Maternal serum free b-human chorionic gonadotropin (b-hCG) normally decreases with gestation after 10 weeks and maternal serum PAPP-A levels normally increase. Levels of these two proteins tend to be increased and decreased, respectively, in pregnancies affected by trisomy 21.

PAPP-A and Free B- hCG On average, baby with trisomy 21 will have 2.0 Mom for B-hCG and 0.4 MoM PAPP-A

Basic screening High risk 1/50 Moderate risk Low risk 1/1ooo

Advanced ◦ Nasal bone ◦ Facial angle ◦ Ductus venosus ◦ Tricuspid regurgitation

Professor Kypros Nicolaides.

The fetal nasal bone can be visualized by sonography at 11–13+6 weeks of gestation (Cicero et al 2001). Several studies have demonstrated a high association between absent nasal bone at 11–13+6 weeks and trisomy 21, as well as other chromosomal abnormalities.

Three line

Fronto maxillary angle

GA dependent CRL=45mm, 84’ CRL=84mm, 76’ Above 95% for age=increased risk of trisomy

Ductus venosus

Sample size Angle Filter sweep speed

Tricuspid regurgitation

Fetal heart rate In normal pregnancy, the fetal heart rate (FHR) increases from about 100 bpm at 5 weeks of gestation to 170 bpm at 10 weeks and then decreases to 155 bpm by 14 weeks. At 10–13+6 weeks, trisomy 13 and Turner syndrome are associated with tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia (Figure 5; Liao et al 2001). In trisomy 21, there is a mild increase in FHR.

Urinary bladder

In first trimester ◦ >7mm=megacystitis ◦ 7-15 mm….. ◦ >15mm……