Prenatal Diagnostic Consultation

The reason for the Prenatal Diagnostic Consultation is to detect fetal malformations early in pregnancy. For this reason various ultrasound scans are performed throughout pregnancy.

The first ultrasound performed is before the 11th week of pregnancy to confirm pregnancy.

The next Ultrasound is the Morphological Scan which is performed during the 1st Quarter of pregnancy at between the 11th and 13th week and 6 days.

The 2nd Quarter Morphologic Ultrasound should occur around 21-22 weeks, when the sex of the baby can usually be detected. 

The Morphological Ultrasound is repeated during the 3rd quarter or 32nd  weeks of pregnancy (in some situations between 28th and 36th week). The development of the main organs such as the brain, heart and kidneys, the location of the placenta and the volume of amniotic fluid, among others, are evaluated.

Although any pregnant woman can be followed in the Prenatal Diagnosis Consultation, it is indicated fundamentally in the following risk situations:

• Increased risk for Trisomy;
• Anomalies diagnosed by ultrasound;
• Risk of malformations due to the use of medication and / or radiation;
• Serious maternal diseases;
• Personal or family history of genetic, metabolic or chromosomal disease;
• Previous obstetric complications such as a dead fetus or fetus malformation;
• Significant changes in fetal growth;
• Complicated twin pregnancy;
• Maternal age> 38 years;
• Depending on the situation, specific screening tests may be necessary, such as amniocentesis or chorionic villus biopsy, fetal MRI, fetal echocardiogram, among others.

1st Trimester Ultrasound Scan - When, Why, and How?

When is the Ultrasound Scan performed?

First-trimester ultrasound is performed between 11th and 13th week and 6 days.

What is the reason for this ultrasound?

• To confirm that the pregnancy is developing and that it is inside the uterus;
• To determine the number of babies, thus identifying a twin pregnancy;
• To determine at what stage is the pregnancy and the expected date of delivery;
• To evaluate fetal anatomy. Some malformations can be diagnosed as early as the first trimester. However, there are others that can only be diagnosed or confirmed in the morphologic ultrasound, performed at 21-22 weeks;
• Screening for chromosomal problems (Trisomy 21, 18 and 13). The main purpose of this ultrasound is to calculate the probability of the baby having Trisomy 21 (also known as Down Syndrome), Trisomy 13 or Trisomy 18, depending on the age of the pregnant woman (risk increases as maternal age increases). Several ultrasound markers are evaluated as in sick babies they may show alterations. The most important are the translucency of the neck (small accumulation of fluid in the nape of the neck) and the bones of the nose. To achieve a 95% detection rate, all this ultrasound information should be combined with the results of specific analyses of the mother's blood (biochemical screening);
• Preeclampsia screening. This disease is specific to pregnancy and is identified due to high blood pressure and alterations in the function of some organs  of the pregnant woman (brain, kidney and liver). It can also prevent the growth of the fetus. It is important to identify pregnant women who are at high risk of preeclampsia so that preventive measures are initiated.

How is this Ultrasound Scan performed?

• Most ultrasound scans are abdominal;
• One week before the ultrasound the pregnant woman should have blood collected for biochemical screening. This screening consists in the analysis of two hormones resulting from pregnancy (BhCG and PAPP-A) and then integrating the results in the final calculation of the ultrasound;
• Before the ultrasound the pregnant woman will be seen by the nurse where weight and blood pressure will be measured.

2nd Trimester Ultrasound Scan – When and Why?

When is it performed?
The morphological scan is performed between the 21st and 22nd week. 

What is the reason for this ultrasound?

In the morphological scan the following is evaluated:

• The growth of the baby;
• All organs and systems to exclude malformations, brain, face, heart, gastrointestinal tract, abdominal wall, limbs, kidneys and spine are all closely observed.
• The sex of the baby;
• The location of the placenta;
• The volume of amniotic fluid;
• The passage of blood into the placenta by observing uterine arteries;
• The risk of preterm labor by measuring the cervix.

3rd Trimester Ultrasound Scan – When and Why?

When is it performed?

The 3rd Trimester Ultrasound, also called the developmental ultrasound, usually takes place on  the 32nd week of pregnancy. In specific situations it can also be performed on the 28th and 36th week.

What is the reason for undergoing this ultrasound? 

• The main reason is to assess whether the baby's growth is progressing normally;
• The development of major organs such as brain, heart and kidneys are reviewed;
• The location of the placenta and the volume of amniotic fluid are confirmed;
• The baby's well-being is assessed by studying blood circulation in the umbilical cord and brain;
• Determining the risk of preterm birth by measuring the size of the cervix.