What should I check at 12 weeks of pregnancy?

Many people are trying to be parents for the first time, especially pregnant mothers. They feel nervous or even at a loss. They don’t know how to do many things and are constantly exploring and accumulating experience. At the twelfth week of pregnancy, you need to go to the hospital for some corresponding examinations. Below we introduce what specific examinations need to be done and what we need to prepare in advance?

A. Routine prenatal check-up items:

During the first prenatal check-up, doctors will usually ask expectant mothers to create a pregnancy health care handbook, determine the gestational age, calculate the expected date of delivery, and assess high-risk factors during pregnancy. Routine examinations will include blood pressure, body mass index, fetal heart rate, blood routine, urine routine, blood type (ABO and Rh), fasting blood sugar, liver function and kidney function, hepatitis B virus surface antigen, syphilis spirochete, HIV screening, and electrocardiogram, so that doctors can better understand the physical condition of the expectant mother and fetus. For expectant mothers who have not undergone premarital or pregnancy checkups, thalassemia screening will be added, and those who have pets at home will also need to add parasite checks. It is best to bring the expectant father along to the first prenatal check-up.

B. Key prenatal examination items: NT

Necessity of NT: In my country, doctors generally recommend nuchal translucency scans for people at high risk of Down syndrome, such as pregnant women over 35 years old, those who have given birth to a baby with Down syndrome, or those with a family history of giving birth to a baby with Down syndrome. Although a nuchal translucency scan cannot determine definitively whether the fetus is infected, it can help pregnant women decide whether further diagnostic testing is needed.

A nuchal translucency scan is a screening test used to assess whether a fetus may have Down syndrome. The NT test is different from diagnostic tests such as chorionic villus sampling or amniocentesis. They can provide a definite diagnosis, but the NT test can only indicate the risk. To determine whether the fetus has chromosomal abnormalities, further chromosomal analysis is still required through chorionic villus sampling or amniocentesis.

Interpretation of inspection items

1. NT effect: Fetuses with Down syndrome will have subcutaneous water accumulation, so the skin on the back of the neck will be thicker. If NT detects that the thickness of the fetal neck skin exceeds the standard value, it may be related to fetal chromosomal karyotype abnormalities and other structural malformations. The thicker the NT, the greater the probability of fetal structural abnormalities and chromosomal abnormalities.

In addition to detecting the risk of chromosomal abnormalities, thickening of the fetal nuchal translucency is also related to congenital heart disease.

If the NT test result exceeds the standard value range, pregnant women are advised to undergo follow-up fetal abnormality screening to further confirm the risk of fetal abnormalities so that timely countermeasures can be taken.

2. NT examination method:

(1) During ultrasound examination, the crown-rump length (CRL) and biparietal diameter of the fetus are first measured to determine the ultrasound gestational age. Then the fetal structure is checked in sequence, and some important indicators such as fetal heart rate, fetal movement, the connection between the umbilical cord and the fetus, the development of the fetal limbs, and the intracranial choroid plexus are observed to exclude fetal abnormalities such as holoprosencephaly, choroid plexus cysts, umbilical hernias, and other developmental abnormalities.

(2) The thickness of the nuchal translucency is measured in the sagittal section of the fetal long axis, with the fetal head in a straight line with the spine. Adjust the magnification so that the fetal body occupies about 3/4 of the screen size. The measurement point is placed at the inner edge of two high-echo lines for measurement. These two high-echo lines represent the skin echo and the soft tissue echo on the spine surface respectively, and the part between them is the nuchal translucency.

(3) Take a sagittal section of the fetus along its long axis, with the fetus in a naturally flexed position, and measure the thickest part of the subcutaneous anechoic transparent layer at the nape of the fetus’ neck, from the inner edge of the skin layer to the outer edge of the fascia layer. Measure three times and take the thickest value.[6]

(4) If the measured thickness of the fetal nuchal translucency is ≥3 mm (or ≥2.5 mm and the gestational age calculated based on the fetal crown-rump length is <12 weeks), the pregnant woman is recommended to undergo amniocentesis or chorionic villus sampling for fetal chromosome karyotype analysis.

3. Normal NT value: The nuchal translucency usually increases with the growth of the fetus and gradually disappears after 14 weeks of pregnancy. In China, doctors consider a nuchal translucency greater than 3 mm to be abnormal. Due to different individual conditions, some normal fetuses have more body fluids, which can easily affect the measurement results. If the nuchal translucency is thick, it does not necessarily mean that there is a problem with the fetus.

If the NT measurement is close to 3mm, pregnant women can consult a doctor to decide whether to undergo further examination to clarify the risk of disease. Generally speaking, the thicker the nuchal translucency, the higher the risk of fetal abnormalities. If the thickness has reached 6mm, there is a high risk of Down syndrome and other chromosomes, genetic syndromes and heart problems. At this time, it is recommended to conduct subsequent risk screening to clarify the condition and take countermeasures as soon as possible.

The above is a detailed introduction to the examination items to be done in the hospital at 12 weeks of pregnancy. Pregnant mothers in particular can learn about it in detail. When doing the examination, you must keep yourself relaxed and not too nervous. This examination is mainly to see whether the baby is growing healthily and whether there are any genetic diseases, so generally there is no problem.