Ultrasound Scans

Mr Willam Dennes is a specialist in fetal medicine and can perform ultrasound scans at any time of your pregnancy from 8 weeks of pregnancy. These can be carried in our clinic at the same time as your appointment.

Important scans (and a usual minimal expectation) is a scan at 11-14 weeks and at 20 weeks (Anomaly scans). Additional scans may be indicated for medical reasons (such as twins, placenta location or advanced maternal age). Serial scans at 28, 32 and 36 weeks may be arranged for reassurance and accurate assessment of fetal growth. Current ultrasound fees can be found here.

11-14 week scan (including nuchal translucency scan)

The nuchal translucency refers to the measurement of the fluid behind the fetal neck. The scan is also an accurate way of dating the pregnancy (by measuring the length of the fetus from its head to its bottom; the crown-rump length, or CRL) therefore accurately calculating the expected date of delivery (EDD). Approximately 10% of assisted conceptions result in multiple pregnancy. Early ultrasound scanning can identify multiple pregnancies, and this is the best time to establish whether twins are identical or non-identical (monochorionic or dichorionic). In a very small number of pregnancies (<1%) the fetus has a major abnormality, which may be visible at this early scan. If an abnormality is found the significance and management options will be discussed. The scan is usually carried out trans-abdominally (by scanning the abdomen). It is not necessary to have a full bladder. Assessment of the Nuchal translucency is important in assessing risk of chromosome abnormalities, genetic syndromes and cardiac conditions.

Whilst the majority of pregnancies result in a normal outcome all women (irrespective of their age) have a chance of delivering a baby with a chromosomal abnormality, such as Down Syndrome. This risk can be determined from the mother’s age (date of birth) and this risk increases with maternal age.

Non-invasive prenatal screening (NIPT)

Non-invasive prenatal testing (NIPT) or cell-free DNA screening (cfDNA) is designed to screen for:

• Trisomy 21 (Down syndrome)
• Trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome)
• Sex chromosome aneuploidy (abnormalities in the number of X or Y chromosomes)

In addition, NIPT can also assess fetal sex. This is optional (no additional cost).

NIPT has a high detection rate for these conditions, and has no risk to the fetus. They are however screening (rather than diagnostic) tests. NIPT can be carried out anytime in pregnancy from 10 weeks (when the fetal fraction is sufficient for the test to be carried out). NIPT can be performed in both IVF and twin pregnancies.

We suggest the Illumina test – arranged through TDL in London. Results are usually obtained within 7 days.

The only way to know for certain whether or not the fetus has a chromosomal abnormality is by performing an invasive, diagnostic test such as chorionic villous sampling (CVS), between 11 and 16 weeks or amniocentesis, after 16 weeks.

Anomaly scan

The anomaly scan is a detailed ultrasound caried out between 20-24 weeks. It will assess not only fetal growth and well-being but also is a detailed assessment of the fetal structure and anatomy  (fetal brain, face and lips, heart, stomach, abdomen and kidneys, spine and limbs). If you wish you can find out the fetal sex.  A normal 20 week scan will reduce the risk of both chromosomal and genetic abnormalities. It would be expected to identify the majority (70%) of structural abnormalities. An assessment of fetal well-being is made by assessing fetal growth (biometry), amniotic fluid and Dopplers (blood flow). Placental function can be determined by measuring uterine artery blood flow.

Growth scan

Subsequent growth scans usually assess fetal growth and well-being to assess normal progress of the pregnancy. Measurements of the fetal head, abdomen and limbs will provide an estimate of the fetal weight. Measurement of amniotic fluid and blood flow (Dopplers) is an assessment of fetal well-being. Ultrasound can also confirm fetal presentation (confirm the baby is head down) at the end of pregnancy. 3D imaging can provide imaging of the fetal face – ideally at around 28 to 32 weeks, dependent on fetal position.