First Trimester Screening

📋 What the First Screening Includes

The first prenatal screening (first trimester screening) is a comprehensive assessment performed at 11 weeks + 0 days to 13 weeks + 6 days of pregnancy. The optimal timing is 12-13 weeks, when the fetal crown-rump length (CRL) measures 45-84 mm. Results are most informative within this range.

The screening consists of two mandatory components:

• Fetal ultrasound — evaluation of anatomy and measurement of key markers (nuchal translucency thickness, nasal bone, CRL, etc.). Performed transabdominally or transvaginally.
• Biochemical blood test — measurement of free beta-hCG (free beta subunit of human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein A). Blood is drawn from a vein on an empty stomach.

Together, these two components are called combined screening. The ultrasound and biochemistry results are entered into a specialized program (most commonly the Fetal Medicine Foundation — FMF algorithm), which calculates an individual risk of chromosomal abnormalities based on maternal age, weight, ethnicity, and other factors. The accuracy of combined screening for detecting Down syndrome (trisomy 21) is 90-95%, with a false-positive rate of approximately 5%.

The purpose of screening is not to make a diagnosis but to identify a high-risk group for further evaluation. Screening is voluntary but recommended by the Ministry of Health of Ukraine (Order No. 417) for all pregnant women regardless of age.

🖥️ Ultrasound Markers and Normal Values

During the ultrasound examination, the doctor measures several key markers. Here are the main indicators and their normal values at 12 weeks of pregnancy:

Nuchal translucency (NT) is the most important ultrasound marker of the first screening. According to the Fetal Medicine Foundation (FMF), normal NT at 12 weeks averages 1.6-1.8 mm. Values up to 2.5 mm are considered normal. An NT measurement between 2.5 and 3.0 mm is borderline, and NT above 3.0 mm significantly increases the risk of chromosomal abnormalities. However, even an increased NT does not mean a diagnosis — it is just one factor in the overall risk calculation.

The nasal bone is absent in approximately 60-70% of fetuses with Down syndrome and in only 1-2% of healthy fetuses. This makes it a valuable additional marker, although its absence alone is not a diagnosis.

The doctor also evaluates overall fetal anatomy: skull contours, limb development, anterior abdominal wall, and bladder. At this gestational age, some major congenital malformations can already be detected (anencephaly, omphalocele, etc.).

🧪 Blood Biochemistry: Free Beta-hCG and PAPP-A

The second component of screening is a maternal venous blood test for two markers. Results are expressed in MoM (multiples of the median) — the ratio of the patient's value to the median for the given gestational age. Normal values range from 0.5 to 2.0 MoM.

How to Interpret Abnormal Results

In Down syndrome (trisomy 21), the typical pattern is: free beta-hCG elevated (often >2.0 MoM), PAPP-A decreased (often <0.5 MoM). This combination is characteristic but not diagnostic — similar deviations can occur in normal pregnancies.

In Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13), both markers are usually decreased — both free beta-hCG and PAPP-A below 0.5 MoM.

Low PAPP-A (even with normal free beta-hCG) may also indicate a risk of fetal growth restriction, preeclampsia, and other complications later in pregnancy. Therefore, the doctor may recommend additional monitoring even when chromosomal risk is low.

Important: Biochemical marker levels are influenced by maternal weight, smoking status, ethnicity, method of conception (IVF), and the number of fetuses. The laboratory adjusts for these factors when calculating MoM. Therefore, absolute values may differ between women — what matters is the corrected MoM value.

📊 How to Interpret Screening Results

The result of combined screening is an individual risk, expressed as a ratio such as 1:1,500 or 1:150. This means that among a certain number of pregnancies with similar parameters, one will result in a baby with the given condition.

What the Risk Numbers Mean

• 1:10,000 — very low risk (1 in 10,000)
• 1:1,000 — low risk
• 1:500 — moderate risk
• 1:250 — threshold level (in most laboratories)
• 1:100 — high risk
• 1:50 — very high risk

Threshold risk is the cutoff that separates "low risk" from "high risk." In most laboratories and protocols (including FMF recommendations), the threshold is 1:250 or 1:300. If your risk is "lower" than the threshold (e.g., 1:1,500 with a threshold of 1:250), the result is considered negative (low risk). If the risk is "higher" than the threshold (e.g., 1:80), it is considered positive (high risk).

What Is MoM?

MoM (multiples of the median) is the ratio of your value to the median (average value) for the given gestational age. For example, if the median free beta-hCG at 12 weeks is 40,000 mIU/mL and yours is 80,000 mIU/mL, your MoM = 2.0. Normal range: 0.5-2.0 MoM. Values outside this range require attention but are not a diagnosis on their own.

It is important to understand: screening is not a diagnosis. A positive screening result (high risk) only means the woman falls into a group for which further evaluation is recommended. Statistically, among women with a positive screening, only 2-3% have a confirmed chromosomal condition. In other words, most "positive" results turn out to be false positives.

Screening results should be interpreted by a geneticist or obstetrician-gynecologist who considers all factors together. Do not attempt to interpret individual numbers on your own.

⚠️ What If the Risk Is High?

A high-risk screening result is not a diagnosis — it is a reason for further evaluation. Your doctor may recommend one of two approaches:

NIPT (Non-Invasive Prenatal Test)

NIPT is a maternal blood test that analyzes cell-free fetal DNA circulating in the mother's blood from weeks 9-10 of pregnancy. The test determines the risk of trisomy 21 (Down syndrome), 18 (Edwards), and 13 (Patau) with accuracy exceeding 99% for trisomy 21 and approximately 97-99% for other trisomies.

Advantages of NIPT: safe (no risk to the fetus), highly accurate, results in 5-10 business days. Limitation — it is still a screening test, not a diagnosis. A positive NIPT requires confirmation with an invasive procedure.

Invasive Diagnostic Testing

If NIPT is positive or if the woman wants a definitive diagnosis immediately, an invasive procedure is performed:

• Chorionic villus sampling (CVS) — sampling of chorionic villi through the abdominal wall or cervix. Performed at weeks 11-14 of pregnancy. Karyotyping results in 7-14 days.
• Amniocentesis — sampling of amniotic fluid through the abdominal wall. Performed at weeks 16-18 (possible up to week 20). Results in 14-21 days.

Both procedures provide a definitive diagnosis (fetal karyotype) with reliability >99.9%. However, they carry a risk of complications: the risk of miscarriage is approximately 0.5-1% (per ACOG and RCOG data). In experienced centers, the risk may be lower (0.1-0.3%).

The decision about invasive testing is made by the woman together with a geneticist. The doctor explains the risks and benefits of each method, considering the individual situation. There should be no pressure from medical staff — it is the woman's right to choose the next steps.

Algorithm of actions for high risk:

1. Genetic counseling — discussion of screening results
2. NIPT or invasive testing directly (at the woman's choice)
3. If NIPT is positive — invasive confirmation (CVS or amniocentesis)
4. Genetic counseling based on results — discussion of diagnosis and prognosis
5. Decision-making — the woman and her family independently determine the next steps

💰 Where and How Much Does Screening Cost in Ukraine

In Ukraine, the first screening can be done either free of charge or privately:

Free of Charge

At state women's consultations (prenatal clinics), screening is provided free of charge with a doctor's referral. This is guaranteed by the Medical Guarantee Program of the National Health Service of Ukraine (NHSU). Contact your obstetrician-gynecologist, who will issue referrals for the ultrasound and blood test. However, in some regions there may be waiting lists or limited availability of high-quality ultrasound equipment.

Private Clinics (Paid)

Costs vary by city, clinic, and doctor qualifications. Prices are generally higher in Kyiv and other major cities. When choosing a private clinic, look for FMF certification of the doctor performing the ultrasound — this guarantees adherence to international NT measurement standards.

NIPT is offered by several laboratories in Ukraine. Blood samples are often sent to foreign laboratories (USA, Germany, Cyprus), so results may take up to 10-14 business days. Cost ranges from 5,000 to 15,000 UAH depending on the panel (basic — trisomies 21, 18, 13; extended — additional microdeletions and sex determination).

Regardless of where you have your screening, always discuss the results with your doctor. Do not try to interpret the results on your own — only a qualified specialist can properly evaluate the data in the context of your specific pregnancy.

📌 Summary: Key Facts About the First Screening

The first prenatal screening is a safe and informative assessment that helps evaluate the risk of chromosomal abnormalities in early pregnancy. Here are the key facts:

• When: 11+0 to 13+6 weeks of pregnancy (optimal — 12-13 weeks)
• What it includes: Fetal ultrasound + blood test for free beta-hCG and PAPP-A
• Accuracy: 90-95% for detecting Down syndrome (combined screening)
• Result: Individual risk (e.g., 1:1,500 — low, 1:80 — high)
• Threshold: Usually 1:250 or 1:300 — below = low risk, above = further evaluation recommended
• High risk does not equal diagnosis: It is a reason for NIPT or invasive diagnostic testing
• Screening is voluntary but recommended by the Ministry of Health of Ukraine for all pregnant women

Remember: screening was designed to reassure the majority of women (since most results are normal) and to identify those who need additional evaluation in a timely manner. Trust your doctor, ask questions, and do not panic about numbers — they are just one part of the bigger picture.