Modern obstetrics has advanced by leaps and bounds in the last decade, in a harmonious interaction between the specialist and technology. We have gone from being observers to interventionists, but we have achieved a decrease in the rate of invasive procedures in favor of little or no invasive methods thanks to imaging, particularly Sonography, serum studies and non-invasive genetic studies in maternal blood.

With the discovery, the development and worldwide approval of the use of fetal DNA (cffDNA) in maternal blood took a giant step in the non-invasive fetal diagnosis.

Prenatal diagnosis began seriously in the 60s through the use of genetic amniocentesis, was performed late and blind (no Sonography) only in high-risk populations and maternal age over 35 years, leaving aside the vast majority of pregnant women, with a relatively high cost and not without complications (5% of abortions). Even though it represented a great advance, it was an inadequate diagnostic test to serve the general pregnant population, amniocentesis is not a screening test, it is a diagnostic test. Therefore, screening or screening tests had to be developed to select the high-risk population that would require the amniocentesis diagnostic test.

Non-invasive Prenatal Diagnosis

The oldest and archaic method in prenatal diagnosis was the diagnosis of pregnancy, which was only done when there was enough abdominal growth and fetal movements to determine without a doubt the presence of a pregnancy with a live fetus

The auscultation of the fetal heart to determine fetal vitality was first described in 1600 (ear against the abdominal wall of the mother), subsequently (1819) the fetal stethoscope was developed, in 1931 the first rudimentary electronic fetal stethoscope was developed and in 1964 the first Doppler device for continuous fetal frequency monitoring

In the 70’s, the first screening tests were performed to detect risk of hidden congenital malformations between weeks 15 and 21 of pregnancy, Spina Bifida, a relatively frequent disabling malformation, by measuring the AFP (Alpha Feto Protein) in blood. maternal It is the first screening test applicable to large populations. Later it is used for the detection of Down Syndrome (Trisomy 21) and other Trisomies, some time later (18 and 13).

In the 80-90s new promising markers are added, Human Chorionic Gonadotropin (hCG), Estriol (E3) and Inhibin A (iA) to improve the detection rates of chromosomal disorders through the use of Double Tests (AFP, hCG), Triples (AFP, hCG and E3) and Quadruples (AFP, hCG, E3 and iA).

In the 90s, the use of large-scale obstetric ultrasonography was initiated thanks to technological advances, routine medical training and the reduction of costs; The real revolution in fetal diagnosis begins, seeing the embryo and the fetus as patients. Clinical Sonography was already in use for 20-30 years but the images were descriptively poor and of low resolution, insufficient for the precise anatomical diagnosis that we know today.

In the first decade of 2000, new screening procedures were established, unifying serological tests in maternal blood with fetal data evaluated by Sonography, the Combined Test, surpassing the previous ones because it was more sensitive to detect fetal risk in an earlier gestational age, 11 to 13.6 weeks. The Combined Test includes the ultrasonographic measurement of the Nucal Translucency by Sonography (see Genetic Eco of the First Trimester ) and 2 maternal serum markers: PAPP-A (Plasma Protein A Associated with Pregnancy) and the b hCG (free fraction of the beta fraction of the hCG). Thus, serological tests progress towards the First Trimester to allow early diagnosis and management of pregnancy complicated by fetal chromosomal malformations.

The First Trimester Genetic Ultrasound that was developed from the beginning of this century as a systematic study of the fetus from 11 to 13.6 weeks has generated deep knowledge about fetal life and has improved exponentially the diagnostic and research capacity of high-risk teams. resolution by detecting small indirect markers of chromosomal, genetic diseases and unambiguous alterations of most isolated congenital malformations or detectable syndromes. High resolution sonography in experienced hands is not only an excellent screening method but also has a great potential to diagnose hundreds of minor and major congenital malformations.

The detection and study of free fetal DNA in maternal blood is the most recent advance in early chromosomal and genetic non-invasive clearing, starting at week 10 of gestation. It is based on the detection of known genetic abnormalities (pathological DNA sequences) in the fetal DNA (placental) that circulates freely in the maternal plasma during the current pregnancy. Although it is a very advanced test does not meet certain characteristics to say it is diagnostic, so it is considered a method of screening or research. If an unfavorable result is obtained, an invasive diagnostic procedure must be performed

Invasive Prenatal Diagnosis

Invasive methods are diagnostic and include the definitive procedures to determine the chromosomal or genetic diagnosis that is suspected due to anomalous findings in the ecosonographic study or high risk results in serological or genetic tests of fetal DNA: Amniocentesis, Cordocentesis and Corial Vellosity Biopsy .

These tests are based on obtaining samples of fetal origin, amniotic cells, placental tissue or fetal whole blood. Because they are invasive, they can lead to the loss of pregnancy, a remote but existing event.

Non-invasive Prenatal Diagnosis

The cornerstone of non-invasive fetal diagnosis is fetal ecosonography. There is no method that exceeds it in diagnostic amplitude, safety, cost, effectiveness and reproducibility.

As a screening test it helps to detect chromosomal or genetic syndromes indirectly due to the presence of markers that indirectly suggest the potential presence of abnormal syndromatic conditions.

As a diagnostic procedure, it has a very high detection rate of unequivocal structural anomalies in multiple organs and systems, that is, it can issue accurate and unambiguous diagnoses of multiple anomalous conditions of almost all fetal organs. For example, an isolated primary congenital heart disease can not be detected by any method of screening or genetic or chromosomal diagnosis (the results of these tests would be negative, indicating a healthy baby), it is a structural antenatal diagnosis exclusively demonstrable by Sonography.