Pregnancy Ultrasound Scans: A Complete Guide for Expectant Parents
Medically reviewed by Daniela Stan MSc Medical Ultrasound, Consultant Sonographer & Clinical Director — July 2026
Types of Pregnancy Ultrasound Scan
Pregnancy ultrasound scans are performed at different stages of pregnancy to assess fetal development, confirm viability, establish gestational age, screen for chromosomal abnormalities, assess fetal growth and wellbeing, and determine fetal position. The NHS provides two routine scans: the dating scan at 10–14 weeks and the anomaly scan at 18–21 weeks. Private scans can be booked at any stage of pregnancy, with or without a GP referral.
Early Pregnancy Scan (6–10 Weeks)
An early pregnancy scan confirms the location of the pregnancy (intrauterine vs ectopic), establishes viability by detecting a fetal heartbeat, and provides an accurate gestational age estimate. It is particularly valuable for women who have experienced previous pregnancy loss, IVF patients, and those with symptoms of concern such as bleeding or pain.
At 6–8 weeks, the scan is typically performed transvaginally (using an internal probe) for the clearest images. From 9–10 weeks onwards, a transabdominal approach is usually sufficient. Our early pregnancy scan is available from £235.
Dating Scan (10–14 Weeks)
The dating scan measures the crown-rump length (CRL) of the fetus to establish an accurate estimated due date (EDD). It also assesses the number of fetuses (identifying twins or higher-order multiples), fetal viability, and the nuchal translucency (NT) measurement — a marker used in combined first-trimester screening for chromosomal abnormalities including Down's syndrome. Our baby dating scan is available from £235.
Baby Gender Scan (16–22 Weeks)
Fetal sex can be determined on ultrasound from approximately 16 weeks, with accuracy increasing with gestational age. At 18–22 weeks, accuracy is typically 95–99% in experienced hands. Our baby gender scan is available from £235 and can be combined with a growth and wellbeing assessment.
Growth and Wellbeing Scan (28+ Weeks)
Growth scans assess fetal biometry (head circumference, abdominal circumference, femur length), estimated fetal weight, amniotic fluid volume, placental position, and Doppler blood flow in the umbilical artery. They are recommended for pregnancies with risk factors for fetal growth restriction (FGR), including maternal hypertension, diabetes, previous FGR, and multiple pregnancy. Our growth ultrasound scan is available from £235.
From Our Practice: The Reassurance Scan
A pattern we see regularly in our pregnancy scanning service is the woman who has experienced a previous miscarriage and is now pregnant again. She is anxious in the early weeks and wants reassurance that the pregnancy is progressing normally before her NHS dating scan at 12 weeks. She books an early pregnancy scan at 7–8 weeks. In the majority of cases, the scan confirms a viable intrauterine pregnancy with a normal fetal heartbeat, and the patient leaves significantly reassured. In a small proportion of cases, the scan identifies a missed miscarriage or an ectopic pregnancy — findings that require urgent clinical management. In these cases, the early scan has enabled earlier intervention and avoided the distress of a missed miscarriage discovered later in pregnancy.
Drawn from typical cases seen at our Marylebone clinic. This is a composite scenario representative of patterns we encounter regularly.
Private Pregnancy Scans vs NHS Scans
NHS pregnancy scans are provided free of charge at 10–14 weeks (dating) and 18–21 weeks (anomaly). Private scans are available at any gestational age, without a referral, and typically offer shorter waiting times, longer appointment slots, and the option to bring a partner or family member. Private scans are not a replacement for NHS scans — the NHS anomaly scan at 18–21 weeks is a comprehensive structural survey that is not replicated by a private gender or growth scan.
For a detailed comparison, see our article on NHS vs private pregnancy scans.
Frequently Asked Questions
Is ultrasound safe during pregnancy?
Yes. Diagnostic ultrasound uses sound waves, not ionising radiation, and has an excellent safety record in pregnancy. BMUS and NICE recommend that ultrasound should only be performed when there is a clinical indication — but there is no evidence of harm from diagnostic ultrasound at standard clinical settings.
How early can a heartbeat be detected on ultrasound?
A fetal heartbeat can typically be detected transvaginally from approximately 6 weeks of gestation (measured from the first day of the last menstrual period). Transabdominal detection is reliable from approximately 7–8 weeks.
Do I need a full bladder for a pregnancy scan?
For early pregnancy scans performed transvaginally, a full bladder is not required. For transabdominal scans from 10 weeks onwards, a moderately full bladder improves image quality. Specific preparation instructions are provided at booking.
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Ready to book your pregnancy ultrasound scan?
Our consultant sonographers are available Monday to Saturday at our Marylebone clinic. No GP referral needed. Instant verbal results. Written report within 24 hours.
References
- NICE. Antenatal care. NG201. 2021 (updated 2023). Available at: https://www.nice.org.uk/guidance/ng201
- British Medical Ultrasound Society. Guidelines for the safe use of diagnostic ultrasound equipment. 2010 (reviewed 2023). Available at: https://www.bmus.org/
- Royal College of Obstetricians and Gynaecologists. Fetal Growth Restriction. Green-top Guideline No. 31. 2023. Available at: https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/
