Antenatal Screening 101: Understanding Tests for a Healthy Pregnancy

Antenatal screening plays a vital role in ensuring the health and well-being of both mother and baby during pregnancy. These tests, offered at different stages of pregnancy, help monitor foetal development, detect potential complications, and support informed decision-making. While not all tests are necessary for every pregnant woman, understanding their purpose and timing is crucial for navigating pregnancy care effectively.

This guide outlines the most common antenatal tests available in the UK, explaining when they’re offered, why they’re conducted, and what they involve.

What Is Antenatal Screening?

Antenatal screening includes a series of tests offered during pregnancy to check for potential health concerns in the mother or baby. These screenings can detect genetic conditions, monitor foetal growth, and identify risks of complications such as pre-eclampsia or gestational diabetes.

Why Is Antenatal Screening Important?

Detects early signs of health conditions in the baby, such as chromosomal abnormalities or structural issues.

Identifies maternal health concerns, like infections or gestational diabetes.

Provides reassurance and enables informed decision-making during antenatal appointments.

Antenatal Tests by Trimester

First Trimester (Weeks 1–12)

The first trimester is a critical time for confirming the pregnancy, assessing early risks, and establishing baseline maternal health.

Booking Appointment

In the UK, the first antenatal appointment, known as the booking appointment, typically occurs between weeks 8 and 10. This visit includes a detailed medical history review, discussions about lifestyle factors, and initial screenings.

Blood Tests

At the booking appointment, the following blood tests are usually performed:

Blood Type and Rh Factor: To determine if the mother is Rh-negative. If she is, anti-D treatment may be needed later in pregnancy to prevent complications.

Full Blood Count (FBC): Checks for anaemia or other blood conditions.

Infectious Disease Screening: Identifies infections like HIV, syphilis, and hepatitis B.

Rubella Immunity: Ensures the mother is protected against rubella, which can harm the baby if contracted during pregnancy.

Urine Tests

Urine samples are routinely tested for:

Protein: High levels may indicate pre-eclampsia later in pregnancy.

Glucose: Elevated levels could signal gestational diabetes.

Bacteria: Detects urinary tract infections, which are common during pregnancy.

Combined Screening

Offered between weeks 10 and 14, the combined test includes:

Nuchal Translucency Ultrasound: Measures fluid at the back of the baby’s neck to assess the risk of chromosomal conditions like Down’s syndrome.

Blood Test: Checks for specific hormones and proteins associated with chromosomal abnormalities.

Combined screening is optional, and parents may choose whether to proceed based on their preferences.

Second Trimester (Weeks 13–26)

The second trimester focuses on detailed assessments of foetal growth and identifying conditions that may require medical management.

Mid-Pregnancy Ultrasound (20-Week Scan)

The 20-week scan, also known as the anomaly scan, is a detailed ultrasound that checks:

Foetal Development: Assesses the baby’s organs, including the heart, brain, and kidneys.

Placenta Position: Ensures it’s not blocking the cervix (placenta previa).

Amniotic Fluid Levels: Confirms there’s enough fluid to support the baby’s growth.

This scan is offered to all pregnant women in the UK as part of standard antenatal care.

Screening for Gestational Diabetes

Gestational diabetes screening is not routinely offered to every pregnant woman in the UK. It’s typically recommended if you:

Have a BMI over 30.

Had gestational diabetes in a previous pregnancy.

Have a close family history of diabetes.

Are from certain ethnic backgrounds with higher risks.

The glucose tolerance test (GTT), performed between weeks 24 and 28, involves drinking a sugary solution and measuring the body’s response.

Quadruple Test

If combined screening wasn’t performed in the first trimester, the quadruple test is offered between weeks 15 and 20. This blood test checks for markers indicating a higher risk of Down’s syndrome.

Third Trimester (Weeks 27–40)

The third trimester focuses on monitoring foetal well-being and preparing for delivery.

Group B Streptococcus (GBS) Screening

GBS screening is not routinely offered in the UK but may be conducted if:

You had a baby previously affected by GBS.

GBS was detected in your urine earlier in pregnancy.

You go into preterm labour.

If GBS is present, antibiotics are typically given during labour to protect the baby from infection.

Non-Stress Test (NST)

The NST is performed if there are concerns about foetal movement or growth. It monitors the baby’s heart rate in response to movement, ensuring they’re receiving enough oxygen.

Biophysical Profile (BPP)

A BPP combines an ultrasound and NST to evaluate:

Foetal Movements: Ensures the baby is active and thriving.

Breathing Movements: Checks lung function.

Amniotic Fluid Levels: Confirms there’s enough fluid for the baby’s comfort and safety.

Specialised Antenatal Tests

Some antenatal tests are only recommended if initial screenings indicate a higher risk of complications.

Chorionic Villus Sampling (CVS)

CVS involves collecting placental tissue to test for genetic conditions like Down’s syndrome. It’s usually offered between weeks 10 and 13 if combined screening shows a higher risk.

Amniocentesis

Amniocentesis tests a small sample of amniotic fluid for genetic conditions or infections. It’s typically offered from week 15 onwards if required.

Doppler Ultrasound

This specialised ultrasound measures blood flow in the placenta and umbilical cord, ensuring the baby is receiving enough oxygen and nutrients.

Preparing for Antenatal Tests

Tips for Expectant Mothers

Stay Informed: Understand why each test is offered and discuss your options with your midwife or doctor during your antenatal appointments.

Follow Instructions: Some tests, like the GTT, may require fasting.

Ask Questions: If you’re unsure about a test, your healthcare provider can explain the benefits and risks.

Supporting a Healthy Pregnancy

While antenatal tests are crucial, maintaining a healthy lifestyle also plays a significant role in pregnancy outcomes.

Nutrition

A balanced diet with adequate intake of fruits, vegetables, and whole grains supports maternal and foetal health. Supplementing with antenatal vitamins ensures you meet essential nutrient requirements.

Physical Activity

Regular physical activity, such as yoga during pregnancy, strengthens muscles, improves circulation, and promotes relaxation. Joining pregnancy yoga classes ensures safe and effective exercise.

Relaxation and Self-Care

Incorporating relaxation during pregnancy, such as mindfulness or prenatal massage, helps reduce stress and improve overall well-being.

Antenatal screening is a vital part of pregnancy care, offering reassurance and vital insights into maternal and foetal health. Understanding the purpose, timing, and optional nature of many tests helps expectant parents make informed decisions. Regular antenatal appointments and open communication with your healthcare provider ensure that you’re well-prepared for each stage of pregnancy. By combining thorough antenatal care with a healthy lifestyle, you can navigate your pregnancy journey with confidence and peace of mind.