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Prenatal diagnosis is the set of techniques used to detect fetal anomalies. Although most of them do not have treatment during pregnancy, their knowledge is of crucial importance to be able to control pregnancy, as well as to plan the birth at the right time and place to treat the sick newborn.

During a pregnancy three important, high-resolution ultrasounds, are performed with different objectives at each moment.

11-14 weeks’ scan

In this exploration, the ultrasonographic markers of chromosomal anomalies (nuchal translucency, nasal bone …) are evaluated. Their study allows, along with blood markers, perform what is called combined screening and determine the risk of trisomy 21 (down syndrome) among others.

The ability to diagnose combined screening can be significantly improved with figures close to 99-100% through the non-invasive prenatal tests of fetal DNA in maternal blood, whose use has been widespread throughout the world in the last 5 years and have allowed to increase dramatically the diagnosed cases, decreasing the anxiety of the future parents and all without risk.

Tranquility is one of the most reliable non-invasive prenatal tests on the market.

Morphological ultrasound of the 20 weeks

In the middle of gestation, biometrics (fetal measurements) and fetal morphology are evaluated. It is a good time to study the heart, brain, spine, abdomen, limbs, face, etc.

Third trimester scan

Carried out on week 33-34, it allows re-evaluating the anatomy again and mainly confirming the adequate fetal development and growth as well as the volume of amniotic fluid and the fetal presentation (cephalic, breech, etc.) for the delivery.

In twin pregnancies, some additional exploration is performed and in those that share the placenta (monochorionic), the controls are biweekly.

Ultrasound allows a non-invasive and innocuous study of the fetus in depth, both morphologically and in terms of the detection of growth delays that can benefit from close control and even in some cases of severely affected fetuses of premature birth. It also favors the mother-child emotional bond and its normality helps to reduce the anxiety and fear of the future parents.


Dr. Javier Pérez Pedregosa

Gynecologist. Director of Maternal Fetal Medicine Unit. Hospital Sanitas La Moraleja and HM Puerta del Sur, Madrid. Associate Professor of Medicine. Francisco de Vitoria University.