Combined first trimester screening: when to do it and what it detects

Combined screening is a routine exam performed between the 11th and 13th week of pregnancy. It is not diagnostic, that is, it does not give a confirmation, but it only estimates the risk of certain chromosomal anomalies such as Down syndrome, Edwards or Patau. In different regions it is not expressly defined as mandatory but it is often recommended and integrated into booking and public assistance, and widely promoted as a standard and free exam. The test is called “combined” because it combines two checks: - an ultrasound to measure nuchal translucency, i.e. the thickness of a small liquid space behind the neck of the fetus.- a mother's blood test to evaluate the levels of two substances produced by the placenta (PAPP-A and free beta-hCG) .The results are processed together, also including the mother's age and other clinical information, to calculate the specific risk of the fetus.The test does not pose risks to the mother or the child.What happens after the screening? If the risk is high, it does not necessarily mean there is a problem, but the doctor may suggest more in-depth tests such as the fetal DNA test (NIPT) or invasive diagnostic tests (villocentesis or amniocentesis). Screening can be done free of charge in a public hospital or in private centers affiliated with the NHS, with the request of the treating doctor or gynecologist. It is important to book within the 10th week of pregnancy to be sure to perform the test in the right period, between the 11th and 13th week plus 6 days.