Second Trimester Screening Singapore: What Tests Are Involved and Risks

“Do I really need another screening? I already did the first trimester one."

Second-trimester screening serves a different purpose than first-trimester tests. Here's why your doctor recommends it, what it checks for, and how it helps ensure your baby is developing well.

What is second-trimester screening?

Second-trimester screening is a set of prenatal tests offered to you between 15 and 20 weeks of pregnancy to check on your baby's development and health. These tests usually consist of blood tests and ultrasound scans that allow your doctor to assess the likelihood of certain conditions such as Trisomy 21 (Down syndrome), Trisomy 18 (Edwards syndrome) and neural tube defects.

The screening provides risk assessments – not definitive diagnoses. If results show higher risk for any condition, your doctor will recommend additional testing for a clearer picture.

What tests are recommended to be performed?

Second-trimester screening typically includes several tests to check your health and your baby's development. Here's what each test involves and why it's done.

General health screening

Your general health screening during the second trimester helps your doctor to understand your overall wellbeing. At each second-trimester appointment, your doctor will review your health and perform routine checks.

During this consultation, your doctor will ask about your current health, any existing medical conditions, and your family's medical history, including any genetic conditions that may run in your family. You'll also discuss lifestyle factors such as your diet, physical activity, and habits like smoking or alcohol consumption, as these can affect both your health and your baby's development.

Your doctor will then perform a following physical examination to check how your body is adapting to pregnancy.

Fundal height measurement:
- Measuring from your pelvic bone to the top of your uterus to track baby's growth (at 20 weeks, this should measure around 20cm)
Fetal heartbeat:
- Using a Doppler device to check heart rate (typically 120-160 beats per minute)
Swelling check:
- Examining legs, ankles, and feet for edema
Weight tracking:
- Monitoring weight gain since last visit
Blood pressure:
- Checking for any changes, particularly after 20 weeks
Urine testing:
- Screening for protein (preeclampsia indicator) and glucose levels

Foetal anomaly scan (Ultrasound)

The foetal anomaly scan is a detailed ultrasound that allows your doctor to see how your baby is developing. Performed between 20 and 24 weeks of pregnancy, this scan carefully examines your baby's organs and body structures, including the heart, brain, kidneys, spine, and limbs. It can identify certain structural variations or congenital conditions that may need additional monitoring or care after birth.

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Amniocentesis

Amniocentesis is a diagnostic prenatal test that can help doctors diagnose chromosomal conditions such as Down syndrome, Edwards syndrome and Patau syndrome, as well as certain genetic disorders and neural tube defects.

During the procedure, your doctor will collect a small sample of the amniotic fluid that cushions and protects your baby in the womb. This fluid contains cells from your baby that can be analysed to give you clearer information about your baby's genetic health. The test is usually performed between 15 and 20 weeks of pregnancy.

Gestational hypertension screening

High blood pressure during pregnancy, known as gestational hypertension, can occasionally develop even if you've never had blood pressure concerns before. Gestational hypertension screening involves regular blood pressure checks at prenatal appointments to identify elevated blood pressure (≥140/90 mmHg). Your doctor will monitor it regularly, paying particular attention after 20 weeks of pregnancy when certain pregnancy-related blood pressure changes can sometimes occur.

By keeping a close eye on your readings, your healthcare team can identify any changes early and provide appropriate care to keep you and your baby safe. Early detection helps prevent potential complications such as preeclampsia and supports a healthy pregnancy outcome. These regular checks are quick, simple, and one of the many ways your doctor ensures your and your child's well-being.

Oral Glucose Tolerance Test (OGTT)

The Oral Glucose Tolerance Test (OGTT) is an important screening tool used to check how your body processes sugar during pregnancy. This test helps identify gestational diabetes, a condition where blood sugar levels become higher than normal during pregnancy. Gestational diabetes can affect both you and your baby's health, but when detected early, it can be managed effectively with the right care and support.

After drinking the solution, blood samples will be taken at specific intervals (usually at one hour and two hours) to measure how your blood glucose levels change over time.

You'll drink a glucose solution (75g of sugar) and then have blood drawn at one-hour and two-hour intervals to measure your blood sugar response. The test takes a few hours at the clinic but helps ensure proper diabetes management if needed.

Ready to schedule your second-trimester screening appointments? Our obstetrics team at Thomson Medical can help you plan your routine tests. Contact us to arrange your consultation.

When is this screening performed during pregnancy?

Second-trimester screening is typically performed between 15 and 20 weeks of pregnancy, though some components like the detailed anomaly scan are done between 18 and 22 weeks. This timing isn't random, it's carefully chosen because your baby has developed enough for detailed examination, yet it's early enough to provide you with important information and options if any concerns are identified.

This window also coincides with an exciting phase of your pregnancy when many mothers begin to feel their baby's movements for the first time. Your doctor will work with you to schedule these tests at the most appropriate time based on your individual pregnancy and dates.

What is the difference between first-trimester and second-trimester screening?

First-trimester and second-trimester screenings are prenatal tests designed to assess the risk of certain chromosomal abnormalities and birth defects in a developing fetus.

	First trimester screening	Second trimester screening
Timing	Usually performed between 11 and 13 weeks of pregnancy.	Usually performed between 15 and 20 weeks of pregnancy.
Tests	Involves a nuchal translucency (NT) ultrasound and a maternal blood test (PAPP-A and hCG).	involves a maternal blood test (e.g., quad screen or multiple marker screening)
Purposes	Identifies the risk of Down syndrome, Edwards syndrome, and other chromosomal abnormalities, as well as certain birth defects.	Assesses the risk of Down syndrome, Edwards syndrome, neural tube defects (like spina bifida), and some other conditions.
Accuracy	More accurate	Not as accurate as first-trimester combined screening or non invasive prenatal testing (NIPT)

Additionally, your doctor may recommend for you to go for a combined screening which is a combination of first and second-trimester screenings (integrated or sequential screening) to improve detection rates.

Our Specialists in Obstetrics and Gynaecology (O&G)

What to prepare for this screening?

Second-trimester screening requires minimal preparation. Here's what you need to know before your appointment.

Clothing:
- Wear loose, comfortable clothes so your abdomen can be easily accessed for the scan.
Ultrasound:
- The scan may take about 45 minutes. You’ll need to have a full bladder, so try to drink water beforehand.
- You can eat normally before your appointment as no fasting is required
Blood tests:
- Your doctor may order a set of blood tests called multiple markers which tests for:
  - Alpha-fetoprotein (AFP)
  - Human chorionic gonadotropin (hCG)
  - Estriol
  - Inhibin A

Since every pregnancy is unique, it’s best to confirm with your doctor if there’s anything specific you need to prepare.

What do the results mean?

When you receive your screening report, it may show either a screen negative or screen positive result.

Screen Negative:
- This means your baby has a lower chance of having trisomy 21 (Down syndrome) or trisomy 18. It does not mean there is absolutely no chance.
Screen Positive:
- This means there is a higher chance of your baby having trisomy 21 or trisomy 18. It does not confirm that your baby has these conditions.

If your result is screen positive, your doctor will discuss further diagnostic tests to give you clearer answers.

Still have concerns about your results and want further confirmation? Reach out to our specialists in Obstetrics and gynaecology.

Are there any risks for this procedure?

The good news is that second-trimester screening tests, including blood tests and ultrasound scans, are completely safe for both you and your baby. These routine screening tests carry no risk of miscarriage, bleeding, or infection.

However, if your screening results suggest a higher chance of certain conditions, you may be offered diagnostic tests such as amniocentesis or chorionic villus sampling (CVS). These diagnostic tests do carry a small risk of complications, including miscarriage (less than 1 in 200), minor bleeding, or infection. While these risks are small, we know that any risk to your pregnancy can feel significant and worrying.

Your doctor will never rush you into making a decision about diagnostic testing. If it's recommended, you'll have time to discuss the potential benefits of having more definitive information alongside the small risks involved. Your healthcare team will help you weigh these factors based on your individual circumstances, values, and what feels right for your family. Whatever you decide, you'll be supported.

Every pregnancy is unique, and your screening plan should be too. If you'd like to discuss which second-trimester tests are recommended for your individual situation, our obstetrics and gynaecology specialists are here to support you. Request an appointment.

FAQ

What does a second trimester screening test do?

Second-trimester screening assesses the risk of certain birth defects and genetic conditions in the fetus. It also helps determine the likelihood of conditions like Trisomy 21 (Down syndrome), Trisomy 18 (Edward syndrome) and neural tube defects.

Which scan is done in the second trimester of pregnancy?

The 20 week ultrasound, also known as the anatomy scan or anomaly scan, is typically performed during the second trimester of pregnancy, usually between 18 and 22 weeks. This scan assesses the baby's anatomy, including the brain, heart, limbs, and other organs, to detect any potential birth defects or abnormalities.

When is the second trimester screening done?

Second-trimester screening is typically carried out between the 15th and 20th weeks of pregnancy. This crucial period allows providers to collect essential information about the developing foetus through various tests. These screenings are designed to assess the risk of specific genetic conditions and birth defects, thereby providing valuable insights into the baby's health and development. This timeframe is optimal because it offers a balance between early enough detection of potential issues and obtaining clear and comprehensive results.

Will I get results on the same day?

No, you will not receive your second trimester screening results on the same day. This is because the tests taken require the laboratory testing and identification. Results are usually available within 5 business days. Your healthcare provider will discuss the results with you once they are received.

How does your baby develop during the second trimester?

The second trimester screening plays a crucial role in monitoring your baby's health. This is a period of significant growth and development for your baby, making it extra important to screen for potential birth defects and genetic conditions. Knowing how your baby should be developing during this time would give you a better understanding of what to expect.

Organ development:
- Major organs such as heart, lungs, brain and kidneys are largely formed, but continue to mature and develop.
Growth spurt:
- Your baby undergoes a rapid growth phase, increasing in size and weight.
Quickening:
- Mothers typically start feeling fetal movement (quickening) around 16-25 weeks.
External development:
- Your baby develops features like hair, eyebrows, eyelashes, and fingernails.
Movement and activity:
- Your baby becomes more active, with periods of kicking, stretching, and turning.
Organ function:
- The heart, kidneys, and other organs continue to develop and refine their function.

How long does it take to get second-trimester screening results?

Second trimester screening results are typically available within 5 to 10 business days after the blood sample is collected and sent to the lab. Some labs may have a faster turnaround time, with results available in as little as 5 calendar days. Your healthcare provider will receive the results and then discuss them with you.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, schedule an appointment.