Ultrasonography

Ultrasound is referred to as sound waves traveling at a frequency (cycles per second) above 20,000 hertz. In the second half of the 20th century, a great innovation began in pregnant examination with the visualization of the pregnant uterus (womb) and its contents. This development gave rise to the specialty of fetal medicine (perinatology). Pregnancy care is almost unimaginable without ultrasonography, which has become widespread today and is considered almost as the sixth sense.

Ultrasonography in antenatal care includes fetal anatomical evaluation and specialized studies to identify abnormalities in the first and second trimesters of pregnancy. An ultrasound evaluation performed according to standards recommended by international and national associations provides vital information regarding the anatomy, physiology, development and well-being of the fetus. The real-time image on ultrasound is created by sound waves reflected back from the placenta, amniotic fluid, fetal tissue interfaces, and fluids. In the presence of a valid medical necessity, ultrasonography is applied with the principle of having the least possible exposure and gaining the necessary diagnostic information (ALARA principle = as low as reasonably achievable). A causal relationship between diagnostic ultrasonography and known adverse effects in pregnancy has not been demonstrated.

First Trimester Ultrasonography

Early pregnancy can be evaluated using transabdominal, transvaginal, or both. The purpose of ultrasonography in this period;

Detection of intrauterine (intrauterine) pregnancy
Evaluation of suspected ectopic pregnancy
Identifying the cause of vaginal bleeding
Evaluation of pelvic pain (groin pain)
Calculation of gestational age
Diagnosis and evaluation of multiple pregnancies
Detection of heart activity
Chorionic villus sampling
Assisting in locating and removing intrauterine devices
Evaluation of certain fetal anomalies such as anencephaly in high-risk patients
Screening for Down syndrome screening is a measure of translucency of nuchal translucency

Head-to-rump distance (CRL) is the most accurate biometric determinant of gestational age. This measurement, if done carefully, determines the gestational age with a difference of 3-5 days. Gestational sac, starting from the 5th week by transvaginal sonography; An embryo with cardiac activity can be reliably imaged from week 6 onwards. The embryo should be visualized transvaginally when the mean diameter of the sac reaches 20 mm. Heart movements can usually be seen by transvaginal examination when the embryo reaches 5 mm. If cardiac activity is not detected in an embryo under 7 mm, a repeat examination is recommended within a week.

Neck Transparency (NT)

The evaluation of nuchal translucency (nuchal translucency= NT), which is a part of the first trimester chromosomal anomaly (Down syndrome) screening, has a great impact on the number of pregnancies undergoing late first trimester ultrasound examination. It is the largest thickness of the transparent subcutaneous tissue area between the skin and the soft tissue lying on the spine of the fetus behind the neck. 11-14. measured using certain criteria between weeks. There is an increased risk for fetal chromosomal abnormalities (Down syndrome) and various structural anomalies, including cardiac abnormalities, with increased nuchal translucency.

First Trimester Fetal Anomaly Screening

Evaluation of patients with increased risk for selected fetal anomalies is another indication for first trimester ultrasonography. Research in this area needs to be compatible with sonography performed as part of aneuploidy imaging. focused on anatomy that can be seen in weeks. With today’s technology, it has revealed an average detection rate of about 40%. Since the first trimester ultrasound is not reliable in detecting many major anomalies, it should not replace the second trimester anatomical evaluation (detailed ultrasonography).

Second Trimester Ultrasonography (Detailed Ultrasonography)

If abnormal findings are obtained in the standard ultrasonography examination, a detailed anatomical evaluation is performed with the result of the screening test or when an anomaly is suspected in the history, with a targeted examination. Targeted inspection is performed and interpreted by an experienced operator. The sensitivity of sonography for second trimester fetal anomaly screening varies depending on factors such as gestational age, mother’s body structure, fetal position, device characteristics, examination type, operator’s ability, and specific anomaly. For example, maternal obesity is associated with a 20% decrease in fetal anomaly detection rate, regardless of the type of examination.

Conditions requiring detailed fetal anatomical evaluation;

Congenital, genetic or chromosomal birth history
Known or suspected fetal anomaly or presence of growth restriction in an existing pregnancy
Conditions that increase the risk of congenital anomaly in the fetus;
Diabetes in the mother diagnosed before pregnancy or before the 24th week of pregnancy
Conceiving with assisted reproductive technology (IVF)
High body mass