Obstetric / Pregnancy Ultrasounds
Dating / Viability Ultrasound
The first ultrasound in pregnancy is often referred to as the dating scan. It is typically performed before 10 weeks gestation, most commonly around 7-8 weeks gestation.
Why is the scan recommended at 7 weeks?
From 7 weeks the pregnancy sac is usually visible within the uterus, and the embryo can often be seen along with the ability to visualise the fetal heartbeat. Multiple pregnancies (i.e. twin or triplet) can be identified at this gestation also.
Before 7 weeks it may be too early to clearly see the embryo or confirm the fetal heartbeat.
If your pregnancy was conceived using IVF, the dating scan is generally scheduled 5 weeks after the embryo transfer date.
How is the scan performed?
To achieve clear images and the most accurate measurements, preference for a pregnancy under 10 weeks gestation is that it be done using a transvaginal (internally) method.
This method provides high resolution images of early pregnancy structures, is completely safe and routinely used in early gestation. If you opt to decline a transvaginal scan, please speak to our staff on preparation requirements for an abdominal scan.
What will be assessed during the scan?
During the scan, the sonographer will examine:
- The pregnancy sac and embryo
- The crown-rump length (CRL) of the embryo, which is used to estimate your due date.
- The presence and rate of the fetal heartbeat
- Your ovaries and cervix
What if the results are inconclusive?
Occasionally, it may be too early to collect the necessary information to accurately assess the pregnancy. This is not uncommon, especially if ovulation or implantation occurred later than expected.
In such cases, your doctor may recommend a follow up scan after a suggested interval to reassess development and confirm pregnancy viability.
Pre-NIPT Ultrasound
Before having a sample collected for your Non-Invasive Prenatal Testing (NIPT), UCFW offers a pre-NIPT ultrasound (subject to availability) for your peace of mind. The scan is the first part of the process, followed by a maternal blood test.
The pre-NIPT scan serves several important purposes:
- Confirm gestational age – NIPT samples can only be tested once the fetus measures at least 10 weeks. This scan ensures that the pregnancy has reached the appropriate gestation.
- Assess for multiple pregnancies – Twins or triplets can be identified at this stage and it enables the laboratory to accommodate this in their report.
- Update the due date – if this is your first scan it may help to establish a more accurate due date based on fetal measurements.
Once a pregnancy of 10 weeks + gestation is confirmed, the maternal blood sample can be collected and sent for testing.
Speak to your doctor or obstetrician to request a referral for NIPT then contact our clinic to speak to one of our staff about booking your appointment.
First Trimester Ultrasound
The first trimester ultrasound—also known as the early anatomy scan—is typically performed at 13 weeks of pregnancy. At this stage, an exceptional amount of fetal detail can be assessed using advanced imaging techniques.
This scan includes:
- Confirmation of the due date
- Detailed early anatomy of the fetus (brain, face, heart, abdomen, spine, and limbs)
- Measurement of nuchal translucency (NT)
- Evaluation of the placenta
- Assessment of the cervix and ovaries
A combination of trans-abdominal and trans-vaginal ultrasound is usually used to obtain the most accurate and detailed images. While many fetal anomalies were traditionally not identified until the 20-week scan, advancements in ultrasound technology now allow many of these conditions to be detected as early as 13 weeks.
Nuchal translucency (NT)
The NT scan measures the fluid-filled space at the back of the fetus’s neck. To adequately measure the NT, it has to be done before the fetus reaches 13 weeks and 6 days. An increased NT measurement can be associated with chromosomal abnormalities such as Down syndrome, as well as certain structural conditions.
Screening for down syndrome
By 13 weeks, many expectant parents have already completed non-invasive prenatal testing (NIPT), which analyses fetal DNA through a maternal blood sample. Others may choose the First Trimester Combined Screening (FTCS), which combines a blood test, NT measurement, fetal length, and maternal age to assess risk. FTCS is less accurate than NIPT, and some people choose not to undergo any screening. Regardless of the chosen method, NT is always measured, as an increased NT can signal a higher chance of abnormalities.
Pre-eclampsia risk assessment
During the scan, blood flow in the uterine arteries is also measured to help assess the risk of pre-eclampsia—a condition that can affect both mother and baby.
Additional assessments
The scan also evaluates the placenta, amniotic fluid levels, cervix, and ovaries to provide a comprehensive overview of early pregnancy health.
How is the scan performed?
For optimal imaging, both trans-abdominal and trans-vaginal ultrasounds are often used. Vaginal ultrasounds are safe during pregnancy and quite often offers enhance views of the developing fetus, especially in early gestation.
Morphology Scan
A routine ultrasound is offered at around 21 weeks of pregnancy, commonly referred to as the mid trimester scan or morphology scan. This detailed examination plays a vital role in assessing fetal development and maternal anatomy.
What is assessed:
- Detailed fetal anatomy: brain, face, spine, heart, abdomen, limbs, and external genitalia (gender)
- Placental location and structure
- Amniotic fluid volume
- Maternal pelvic anatomy and cervix
This scan is designed to identify major fetal abnormalities. However, it’s important to note that not all abnormalities can be detected at this stage. Some conditions may develop later in pregnancy, while others – such as cerebral palsy, certain biochemical disorders, or some chromosomal abnormalities – cannot be identified by ultrasound.
Limitations of the scan may include:
- Fetal lie (position of baby in the uterus) may limit visibility of certain structures
- Increased distance between the ultrasound probe and fetus (e.g., due to maternal body habitus or fibroids)
Every effort is made during the allocated appointment to obtain all required images. However, occasionally a repeat scan may be necessary to complete the assessment.
Third Trimester Ultrasound
A third trimester ultrasound may be performed any time from 23 – 40 weeks of pregnancy. This scan is not routine for all pregnancies but is commonly recommended in certain situations.
Reasons for a third trimester ultrasound include:
- Baby measuring larger or smaller than expected
- Unclear fetal position (e.g., breech)
- Gestational diabetes or high blood pressure
- Risk factors for pre-eclampsia
- Multiple pregnancy (e.g., twins or triplets)
- Reduced fetal movements
- History of a small baby in a previous pregnancy
What is assessed:
- Fetal growth and estimated weight
- Fetal position
- Amniotic fluid volume
- Placental location and blood flow (via Doppler)
- Cervical length (prior to 28 weeks)
- Review of fetal organs and development
The possibility of obtaining a 3D image of the baby at this scan is entirely dependent on a number of contributing factors, such as fetal position, fluid levels, maternal anatomy and whether there is a clear pocket of fluid in front of the baby at the time of the scan.
