Patient: Examination and laboratory tests: 22 years old, Down’s screening done at 14 weeks + 3 days of pregnancy, Trisomy 21 is 1 to 280 screening result critical risk, Trisomy 18 is 1 to 100,000, screening result low risk, screening item: open neural tube defects (NTD) Screening result: unable to calculate Recommended genetic counseling Treatment: no medication, no surgery since pregnancy! Medical history: first child, no medical history! Is amniocentesis or other tests needed? Doctor: According to the Ministry of Health standards for midtrimester maternal serological prenatal screening, the time frame for midtrimester screening usually refers to 15 weeks to 20+6 weeks of pregnancy. You were screened at less than 15 weeks and therefore cannot perform an open neural tube malformation risk calculation. Down syndrome screening results may use 1/270 as the positive cut-off value (critical value), i.e. a screening result risk rate ≥ 1/270 is a high-risk pregnancy; Trisomy 18 screening results may use 1/350 as the positive cut-off value, a screening result risk rate ≥ 1/350 is a high-risk pregnancy. Of course laboratories can use their own positive cut-off values if they have established them. But they are generally between 1/250 and 1/350. It can be considered low risk according to the Ministry of Health’s midtrimester maternal serological prenatal screening criteria. However, Down’s syndrome screening is only a screening test and has a high rate of false positives and false negatives, requiring amniocentesis for confirmation. For those near the risk threshold, amniocentesis or noninvasive prenatal testing is preferable to rule out risk.