First Trimester Screening with OSCAR Test & 3D Fetal Ultrasound

Discovering you’re pregnant brings joy alongside natural concerns about your baby’s health. First trimester screening, including the OSCAR (One-Stop Clinic for Assessment of Risk) test combined with 3D fetal ultrasound, provides early insights into your baby’s development and chromosomal health. This comprehensive screening approach provides expectant parents valuable information during the 11-14 week period, helping guide decisions and providing reassurance during early pregnancy.

Dr. Harvard Lin

Obstetrician & Gynaecologist

MBBS (SG)|MRCOG (UK)|MMed (OBGYN) (SG)

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Suitability Techniques Process Results Benefits Considerations FAQ Conclusion

First Trimester Screening with OSCAR Test

Besides NIPT (Non-Invasive Prenatal Testing), the OSCAR test (One-Stop Clinic for Assessment of Risk) is another common option for first-trimester screening. While both tests aim to evaluate the risk of chromosomal conditions, they work in different ways. NIPT is a simple blood test performed from 10 weeks of pregnancy that analyses fetal DNA in maternal blood to estimate the risk of chromosomal conditions such as Down syndrome, with higher accuracy than conventional screening. The OSCAR test, typically performed between 11 and 14 weeks, combines a maternal blood test with an ultrasound scan that measures nuchal translucency to calculate chromosomal risk and assess early fetal development.

Although NIPT provides more precise risk estimates, it remains a screening test and may be followed by diagnostic procedures, such as amniocentesis, if the results indicate a higher risk. The OSCAR test, on the other hand, provides broader early pregnancy information, including a structural evaluation of the fetus; however, its accuracy for chromosomal conditions is slightly lower compared to NIPT.

The OSCAR Test incorporates multiple elements in its risk assessment. The biochemical component measures two pregnancy-related hormones in maternal blood: free beta-hCG (human chorionic gonadotropin) and PAPP-A (pregnancy-associated plasma protein A). These markers, combined with ultrasound findings and maternal factors, form the overall risk calculation.

Additionally, 3D fetal ultrasound technology enhances conventional screening by providing three-dimensional images of the fetus’s anatomy. This imaging allows visualisation of facial features, limb development, and organ formation, offering both medical insights and meaningful bonding opportunities for parents as they see their baby’s features in greater detail.

Ideal Candidates

All pregnant women between 11 weeks and 13 weeks 6 days of gestation
Women of any age seeking early pregnancy risk assessment
Couples desiring detailed information about fetal health
Pregnancies conceived through assisted reproductive technology
Women with previous pregnancy complications or losses
Individuals who prefer non-invasive screening before considering diagnostic tests
Parents wishing for early bonding through 3D visualisation
Multiple pregnancies requiring individual fetal assessment

Other Considerations

This screening may also be beneficial for:

Women aged 35 years and above
Family history of chromosomal abnormalities
Parents who have had a child with a genetic condition
Pregnancies with abnormal findings in early pregnancy scans
Women exposed to certain medications or substances of concern
Couples with consanguineous marriages
Parents who are carriers of genetic conditions

Our Obstetrician can help interpret results within the context of your circumstances and guide you through any additional test recommendations based on findings.

Screening Components & Technology

OSCAR Biochemical Analysis

The OSCAR test begins with maternal blood sampling, performed on the same day as the ultrasound scan. Laboratory analysis measures free beta-hCG and PAPP-A levels, comparing them to established ranges for gestational age. Abnormal levels of these markers can indicate increased risk for chromosomal abnormalities or pregnancy complications.

Nuchal Translucency Ultrasound

This specialised ultrasound measurement forms the cornerstone of first-trimester screening. Using high-resolution equipment, sonographers measure the clear space at the back of the baby’s neck. Increased nuchal translucency can suggest chromosomal abnormalities or cardiac defects. Additional markers assessed include the presence of the nasal bone, facial angle, and blood flow patterns.

3D Fetal Ultrasound Technology

3D ultrasound technology transforms traditional flat images into three-dimensional reconstructions. This enables a comprehensive evaluation of fetal anatomy, including facial features, brain structures, spinal alignment, and limb development. The technology captures multiple 2D images from different angles, reconstructing them into 3D images that reveal anatomical details.

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The Screening Process

Pre-Screening Preparation

Before your appointment, ensure accurate pregnancy dating through early ultrasound or last menstrual period records. No fasting is required for the blood tests. Wear comfortable, loose clothing that allows easy access to your abdomen. Many parents choose to bring their partners or a support person, as the 3D ultrasound can be a special bonding experience. You may also be asked to complete any pre-screening questionnaires about medical history, medications, and family genetic history.

During the Screening

The appointment usually takes about 45-60 minutes. It begins with a simple blood draw from your arm. You will then proceed to the ultrasound suite where you’ll lie comfortably while warm gel is applied to your abdomen. The sonographer performs systematic measurements, including crown-rump length for accurate dating and nuchal translucency measurement to assess chromosomal risk.

During 3D imaging, multiple angles of your baby are captured to create detailed images. You’ll see real-time visuals on the screen, and in many clinics, photos or digital copies are provided. The scan also includes a survey of key anatomy, such as brain development, facial features, heart structure, abdominal organs, spine, and limbs.

Immediate Post-Screening

After the scan, you can resume normal activities immediately. Preliminary ultrasound impressions may be shared at the appointment, but the final risk calculation is only available once blood test results are incorporated. Most clinics provide 3D images or videos for you to take home. Results typically become available within 3-5 working days, integrating all components into a comprehensive risk assessment.

Understanding Your Results


Risk Calculation Integration	The results combine multiple factors—maternal age, ultrasound findings, biochemical markers, and pregnancy history—into an individualised risk assessment. These are expressed as ratios (for example, 1:1000), indicating the likelihood of chromosomal conditions.
Low Risk Results	Most women receive low-risk results, generally defined as less than 1 in 1,000. These results suggest a low probability of the conditions being screened for, although they cannot guarantee a completely unaffected pregnancy. Usual prenatal care continues, including the second-trimester anomaly scan around 20 weeks.
High Risk Results	High-risk results, often defined as greater than 1 in 250, indicate a higher probability that warrants further evaluation. In such cases, our Obstetrician may recommend additional testing, such as non-invasive prenatal testing (NIPT) or diagnostic procedures like chorionic villus sampling (CVS) or amniocentesis. Genetic counselling is often suggested to help parents understand the findings and consider next steps.

Our team explains your screening results and guides you on further steps if needed.

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Benefits of First Trimester Screening

Early first-trimester screening in Singapore provides important advantages for pregnancy management and parental preparation. Identifying potential concerns in the first trimester allows more time for decision-making, specialised care planning, and closer monitoring when needed. For many parents, normal results offer reassurance and help reduce anxiety throughout the pregnancy journey.

The screening also enables comprehensive evaluation of fetal development, including the early detection of major structural abnormalities. When combined with 3D ultrasound, it provides clearer visualisation of facial features and movements, enhancing both clinical assessment and parental bonding. In pregnancies where risks are higher, early identification supports timely referral to maternal–fetal medicine specialists for further evaluation. Because the OSCAR test is non-invasive, it does not carry the small miscarriage risks linked to diagnostic procedures such as amniocentesis, while still providing valuable information.

Another benefit is the integrated nature of the OSCAR test. By combining ultrasound findings, biochemical markers, and maternal history, the screening offers more accurate risk assessment compared to individual tests alone. Standardised protocols also help ensure consistent, reliable results across different providers. Documentation from the screening can serve as a useful baseline for tracking fetal growth and development in later stages of pregnancy.

Limitations & Considerations

It is important to understand that first-trimester screening is a screening test, not a diagnostic one. It provides an estimate of risk but cannot confirm or rule out chromosomal abnormalities with certainty. A low-risk result is reassuring but does not guarantee the absence of all conditions, while a high-risk result does not mean a baby is affected. Some parents may experience anxiety from false positive results, while false negatives can give false reassurance.

Technical factors can also influence accuracy. The timing of the test is crucial and must be performed between 11 and 14 weeks of pregnancy. In some cases, maternal body composition may affect ultrasound image quality, and certain fetal positions can make nuchal translucency measurement more challenging, sometimes requiring a repeat scan. Multiple pregnancies add further complexity, as each fetus must be assessed individually.

Finally, couples should be prepared for the emotional impact of the results. High-risk outcomes can cause significant stress even if further testing later confirms no abnormalities. Detailed 3D imaging may also reveal findings that require unexpected follow-up, which can be emotionally challenging. Access to professional support and counselling is an integral part of the screening process to help families navigate these experiences.

Cost Considerations

The cost of first trimester screening in Singapore varies depending on the clinic, the technology used, and whether both biochemical and ultrasound components are included. The OSCAR test typically combines blood tests with a specialised ultrasound for a comprehensive assessment. Some clinics may include 3D ultrasound as part of the package, while others may offer it as an add-on.

Although it represents an additional cost during pregnancy, many couples find value in early screening for the reassurance it provides and the opportunity for early bonding. Early detection of potential issues can also help reduce long-term healthcare costs through timely management. Some clinics may offer package deals that combine first and second trimester screenings, which can be more cost-effective. It is advisable to clarify what is included in the package price and discuss payment options during your consultation.

Frequently Asked Questions (FAQ)

When is the optimal time to have the first trimester screening with the OSCAR test?

The OSCAR test is usually performed between 11 weeks 3 days and 13 weeks 6 days of pregnancy. This period allows accurate measurement of nuchal translucency while providing sufficient fetal development for anatomical assessment. Many parents choose the 12–13 week mark, as it often gives clearer imaging for both measurements and 3D ultrasound. Our Obstetrician may confirm the most appropriate timing based on your pregnancy records.

How accurate is the OSCAR test in detecting chromosomal abnormalities?

When biochemical markers are combined with nuchal translucency ultrasound, the OSCAR test detects about 85–90% of Down syndrome cases and similar rates for other major chromosomal conditions. Accuracy can vary depending on maternal age and individual pregnancy factors. It is important to note that this is a screening test, not a diagnostic test. Our Obstetrician can explain how the results apply to your specific situation.

Is 3D ultrasound safe for my baby during the first trimester?

Yes. 3D ultrasound utilises the same type of sound waves as traditional 2D scans, but they are processed differently to create three-dimensional images. No harmful effects have been reported when scans are performed by trained professionals who follow safety guidelines. Exposure time and settings are kept within recommended limits to ensure safety for both mother and baby.

What if my screening shows high risk?

A high-risk result does not mean your baby has a chromosomal condition. Our Obstetrician can discuss additional options, which may include non-invasive prenatal testing (NIPT) or diagnostic procedures such as chorionic villus sampling (CVS) or amniocentesis. Genetic counselling may also be recommended to help you understand the findings and consider your next steps. In many cases, follow-up testing confirms that the pregnancy is unaffected.

Can I eat before the OSCAR blood test?

No fasting is required for the OSCAR test. You can follow your usual diet before your appointment. Staying hydrated helps with blood collection and may improve ultrasound imaging. If you experience morning sickness, a light meal before your visit may help you feel more comfortable during the procedure.

Will I definitely see my baby’s face with 3D ultrasound at this stage?

At 11-14 weeks, facial features are still developing but often visible on 3D ultrasound. The clarity of images depends on factors such as fetal position, amniotic fluid levels, and the location of the placenta. Our Obstetrician can try different angles to obtain good views, but it may not always be possible to capture a perfect image at this stage.

Conclusion

First-trimester screening with the OSCAR test and 3D fetal ultrasound offers expectant parents valuable insights during early pregnancy. By combining biochemical testing with detailed imaging, this non-invasive assessment provides valuable information during a critical stage of pregnancy.

While the screening cannot give a definitive diagnosis, it supports informed decision-making and helps guide appropriate prenatal care. Whether the results bring reassurance or highlight the need for further evaluation, early screening plays a crucial role in pregnancy management.

Ready to Take the Next Step?

If you’re in your first trimester and considering comprehensive screening, our Obstetrician can help you understand your options. Book your appointment today to learn more.

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Dr. Harvard Lin

Obstetrician & Gynaecologist

MBBS (SG)|MRCOG (UK)|MMed (OBGYN) (SG)

Dr. Harvard Lin is renowned for his expertise in female pelvic medicine and reconstructive surgery.

Dr. Lin’s journey in medicine began at the prestigious National University of Singapore, where he earned his Bachelor of Medicine and Bachelor of Surgery (MBBS). His commitment to excellence led him to further his education by becoming a Member of the Royal College of Obstetricians and Gynaecologists (MRCOG) through the Royal College of Obstetricians and Gynaecologists in the United Kingdom. He also holds a Master of Medicine (Obstetrics and Gynaecology) from the National University of Singapore.

As the Chief Coordinator of Gynaecologic Services at the National University Health System (NUHS), Dr. Lin plays a pivotal role in ensuring the highest quality care for women’s health. His leadership is also evident in his position as the Deputy Clinical Director of Obstetrics and Gynaecology at NUHS, where he contributes to shaping gynaecologic practices and growth across the cluster including Ng Teng Fong Hospital, Alexandra Hospital and Jurong Medical Centre.

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