Prenatal checkups

Prenatal checkups

Cervical translucency has been a basic prenatal ultrasound examination for several years now. It takes place in the first trimester of pregnancy (11⁺¹ to 13⁺⁶ weeks of amenorrhea).

This is a measurement made in the back of the neck of the fetus and gives us information about a possible chromosomal abnormality (Down syndrome or others) or some other congenital disorder (eg heart disease). Generally, the higher nuchal translucency, the greater the chance that there is some abnormality in the fetus.

This value (measured in mm), combined with the age of the mother, the gestational age and with the measurement in the mother’s blood of the proteins PAPP-A and free β chorionic gonadotropin, gives us a probability of the birth of a child with a chromosomal abnormality ( Combined Test). We consider that if the value of the combined test is greater than or equal to 1/300, then there is an increased probability that the fetus suffers from Down syndrome.

This means that out of 300 mothers who have the same result on the Combined Test, 1 mother is carrying a fetus with Down syndrome. In these cases, some invasive method such as trophoblast retrieval or amniocentesis is suggested to the expectant mother, but methods that involve a risk of miscarriage (<1%).

Alternatively, we can also recommend the measurement of free fetal DNA with a simple blood test in the mother with a reliability that exceeds 99%. In general, we should keep in mind that with the Combined Test we diagnose 85% of fetuses with Down syndrome, with 5% false positive results. In these cases, the first test is usually done with a simple blood test on the mother, and if a mutation is found that indicates that she is a carrier, then the same test is performed on the father. If the father is also found to be a carrier then the next step will be to detect the mutation in the baby as well by taking amniotic fluid (amniocentesis) or taking a sample of trophoblast. But because every couple is different and every pregnancy unique, the treatment is individualized and adapted to each case.