FIRST TRIMESTER- NUCHAL TRANSLUCENCY
This ultrasound is performed from 11 weeks and 1 day to 13 weeks and six days (CRL 45mm – 84mm).It is usually done transabdominally, bBut in some cases it may be necessary to have the scan transvaginally.
Objectives of ultrasound
Exact Pregnancy Age Determined: This is especially important for women who cannot remember the date of their last period, have irregular menstrual periods, or have conceived while breast-feeding or just after discontinuing the contraceptive pill. We measure the size of the fetus and then calculate the probable date of birth (40 weeks).
Risk Assessment for Down Syndrome and Other Chromosomal Abnormalities: Every woman should receive an assessment of her individual risk for this pregnancy. This is calculated taking into account the mother’s age, the measurement of two hormones in her blood (Papp-a and free beta-chorionic gonadotropin) and 4 ultrasound markers, which are: nuchal traranslucenecy (the fluid behind the fetal neck) that is and the most important marker, the nasal bone, the blood flow to the right side of the fetal heart (in the tricuspid valve) and the blood flow to the fetal ductus venosus canal (a small vessel in his liver). Parents will receive full advice on the importance of this risk and the various options for further testing.
Diagnosis of Multiple Pregnancy: About 2% of natural pregnancies and 10% of IVF conceptions result in multiple pregnancies. An ultrasound scan can determine if both fetuses are developing properly and if babies share the same placenta, which can lead to pregnancy problems. In such cases, it would be advisable to monitor pregnancy more closely.
Diagnosis of some major congenital abnormalities: Significant abnormalities may be visible at this gestational age, but a 20-week ultrasound scan is also required.
Diagnosing Early Pregnancy Failure (regression): Unfortunately, 2% of women who come for cervical ultrasound are found to have died, often several weeks before and without any warning. Couples will receive full advice on the possible causes of this problem and the options for future action that may be necessary.
Estimation of risk of preeclampsia and intrauterine growth retardation: In all patients at the end of the examination blood flow to the mother’s arteries will be measured ultrasound by Doppler examination. The result of this test can tell us which women are at increased risk of developing preeclampsia before 34 weeks, as well as which embryos are at risk of delaying their development in the third trimester.
Early Childbirth Risk Calculation: In all patients at the end of the test if they wish, the cervical length will be intermittently measured. We know that during pregnancy, the cervix must be long and closed. Women who have a short cervical screening increase the risk of preterm birth. The treatment in this case is proportionate to the problem.
Personalized Risk for Down Syndrome
The vast majority of babies are normal. However, all women, regardless of their age, have a small risk of having a child with physical or mental disabilities. In some cases the abnormality is due to a chromosomal abnormality such as Down syndrome.
The only way to know for sure if the fetus has a chromosomal abnormality is through a diagnostic invasive examination, such as chorionic duct staining (CVS) or amniocentesis. However, these tests have the risk of elimination of 1%.
It is up to you and your partner to decide whether or not the risk for the fetus having chromosomal abnormalities is high enough to warrant an invasive test. As a guideline, an invasive examination is usually offered if the risk for Down Syndrome is 1 in 300 or more.
The most accurate method for assessing the risk of the fetus having Down syndrome is carried out from the 11th to the 14th week of pregnancy and depends on the following:
- Mother’s age
- Amount of fluid behind the fetal neck (cervical slide)
- Presence or absence of fetal nasal bone
- Fetal heart rate
- The flow of blood through the tricuspid valve of the fetal heart
- The flow of blood through the vein to the fetal liver
- Presence or absence of any structural abnormalities
Level of the two hormones (free β-hCG and PAPP-A) in the mother’s bloodAfter the ultrasound, based on all of the above factors, the estimated risk for Down Syndrome will be discussed with you. Only you can decide whether you want to undergo an invasive diagnostic test. Regardless of whether or not you decide to have an invasive examination, a detailed ultrasound at 20 weeks is recommended to check for structural abnormalities in the fetus.