Pregnancy Screenings and Scans

Prenatal screening tests encompass various tests that your doctor recommends for you during pregnancy. There are additional tests and scans that you may want to do to get rid of certain doubts.

These screening tests begin at your first prenatal appointment and are mostly non-invasive. A screening test only tells you if you are at risk, or high probability of a particular condition.

Once you notice the early signs of pregnancy and take a test to confirm pregnancy, the next step is to go through what to do after a positive pregnancy test, a large part of which is screenings and scans. Listed below is details of what each one entails:

FIRST TRIMESTER SCREENING

The first-trimester screening or 12-week scan is a prenatal test that gives you information at an early stage about certain chromosomal conditions that your baby might be at risk at. This focuses particularly on trisomy 21, commonly referred to as Down syndrome, and trisomy 18, also called Edwards syndrome. The 12-week scan tells you the number of babies you are having, calculates the age and the delivery date of the baby and screens the baby for any common chromosomal conditions. Combined first trimester screening uses a blood test and a nuchal translucency ultrasound. The tests have different timing windows, so check when to book each with your care team.

There is a blood test that measures pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (HCG) and indicates the level of these pregnancy-specific- substances in the mother’s blood.
An ultrasound exam is conducted for nuchal translucency. This measures the size of the clear space in the tissue at the back of the baby’s neck.

What are the risks and what should you do to prepare yourself for the test?

Combined first trimester screening involves a blood test and ultrasound. Ask the clinic how to prepare, including any bladder or food and drink instructions. Australian ultrasound preparation guidance.

Why is the first trimester screening done?

Combined first trimester screening estimates the chance of particular chromosome conditions, including Down syndrome and trisomy 18. It does not diagnose them. Trisomy 18 is a serious condition, but an individual prognosis should be discussed with specialists rather than presented as a certain age of death. Screening information; Australian trisomy information.

This is one of the first prenatal screening tests and gives you results at an early stage during the pregnancy. The first trimester screening is an optional test and evaluates if the mother is at an increased risk of carrying a child with Trisomy 18 or down syndrome. It does not tell you if the baby will be born with one of these conditions.

This first trimester screening sets the course of action for the future pregnancy – taking decisions about other diagnostic tests, mentally preparing you for caring for a child with special needs (if the baby is at a high risk of chromosomal abnormality) and taking treatment and management decisions post-delivery.

Please note that this is just an indicative test – a low risk does not guarantee that baby will be born without any abnormalities and similarly a high risk is no sure shot reason for your child to have down-syndrome.

If everything comes out fine during the tests, it is believed to be one of the most amazing moments for the parents to be. You see your baby for the first time, you get to hear the heartbeat and if you are lucky, you may see some movements as well.

Ask your clinician which screening pathway is appropriate for your stage of pregnancy and previous tests. NIPT is another screening option from 10 weeks. It estimates the chance of certain chromosome conditions and is not a diagnosis. Ask your clinician about the options, limitations and costs. Additional screening is not automatically needed for everyone. Prenatal screening options.

SECOND TRIMESTER SCREENING

The second trimester screening popularly known as the 20th-week scan or anatomy scan is scheduled between Week 18 and Week 22 of your pregnancy. It checks the growth and development of the baby, the positioning of the placenta, may show the baby’s sex if you want to know, scans the body parts and checks any spinal issues like spina bifida, limb abnormalities and heart defects. It may also indicate if your baby has a genetic condition.

Second trimester maternal serum screening may be an option depending on your stage of pregnancy and earlier tests. It is not a compulsory addition to every anatomy scan. Ask your clinician what information it could add. Australian screening information.

Why is the 20th-week scan done?

Evaluate the baby’s growth. Your health care provider takes measurements during the ultrasound to determine if your baby is growing at a normal rate.

The scan examines structures such as the spine and checks development. Your clinician interprets the findings in context; a heart-rate number alone is not a wellbeing test. Ultrasound information.

Assess the risk of placenta previa – The placenta is the source of vital nutrients and oxygen-rich blood for the baby. The ultrasound studies the amniotic fluid levels (the fluid that surrounds the baby in the uterus) and any placenta complications that require special attention. Too little or too much of the fluid is not good.

Identify any birth defects or abnormalities – An ultrasound helps to check for congenital heart defects which is extremely common by evaluating the function of the four chambers of the heart.

Ultrasound can identify some structural differences and findings that may prompt further assessment. It cannot identify every genetic condition or guarantee normal organ function. Australian ultrasound guidance.

Investigate and possible complications – They check for premature labour possibilities using a transvaginal ultrasound wand to inspect the cervix. Ideally, it should be closed and long, however, if it is shortened or/ and opened the risk of premature labour is high

Why is the quad screen done?

Second trimester blood screening estimates the chance of certain conditions; it cannot diagnose them. Which conditions are included depends on the test offered.

Down syndrome (Trisomy 21): This is a chromosomal abnormality that causes lifelong intellectual and developmental impairment. It also leads to health problems for certain children.

Trisomy 18: Trisomy 18 can cause serious health and developmental difficulties. The outlook varies and should be discussed with specialists.

Spina bifida: Spina bifida is a birth defect in the spinal cord and the bones of the spine. It occurs when a part of the neural tube is unable to develop or close properly.

Abdominal wall defects: these are birth defects where the baby’s abdominal organs or intestines stick through the belly button.

Pregnant woman having an ultrasound examination with a healthcare professional.

THIRD TRIMESTER SCREENING

Later-pregnancy tests and monitoring have different purposes. Your clinician will discuss what is appropriate for your circumstances; not all of the tests listed below are routinely needed. Results guide care but cannot guarantee wellbeing. Australian antenatal test guidance.

Biophysical profile: A biophysical profile may be used when more assessment is needed. It combines observations such as movement and amniotic fluid with other information to help assess the baby’s wellbeing.

Group B streptococcus screening may involve a vaginal and rectal swab around 35 to 37 weeks, depending on your service. If you carry GBS or have relevant risk factors, your team may recommend intravenous antibiotics during labour to reduce the risk of infection in your baby. Australian GBS guidance.

A non-stress test may be recommended when extra assessment is needed. The reason and frequency are individual decisions for your care team, rather than an automatic weekly schedule. Fetal monitoring guidance.

A fetal monitor is strapped across the mother’s abdomen and it measures the baby’s heart rate as it moves. This test is also used to monitor overdue babies.

Electronic fetal heart-rate monitoring may be recommended during pregnancy or labour for particular reasons. Ask your team what the test can show, its limitations and how it will guide care. Tests involving contractions are not a routine requirement for every high-risk pregnancy and should only be discussed and performed through specialist care. Australian fetal monitoring information.