Ultrasound Scans

This is an ultrasound examination that is usually carried out at 7-10 weeks of pregnancy.

The aims of this scan are to determine the number of embryos present and whether the pregnancy is progressing normally inside the uterus.

This scan is useful for women who are experiencing pain or bleeding in the pregnancy and those who have had previous miscarriages or ectopic pregnancies.

The figure on the left shows a normal pregnancy at 7 weeks of gestation. The figure on the right shows the empty sac of an anembryonic pregnancy at 7 weeks.

This scan is carried out from 11 weeks + 3 days to 13 weeks + 6 days. The scan is usually performed transabdominally but in a few cases it may be necessary to do the examination transvaginally.

 Aims of the nuchal scan

• To date the pregnancy accurately. This is particularly relevant for women who cannot recall the date of their last period, have an irregular menstrual cycle, or who have conceived whilst breastfeeding or soon after stopping the pill. We measure the size of the fetus and from this we calculate the expected date of delivery.
• To diagnose multiple pregnancy. Approximately 2% of natural conceptions and 10% of assisted conceptions result in multiple pregnancy. Ultrasound scanning can determine if both babies are developing normally and if the babies share the same placenta which can lead to problems in the pregnancy. In such cases it would be advisable to monitor the pregnancy more closely.
• To diagnose major fetal abnormalities. Some major abnormalities may be visible at this gestation. However it will still be necessary to have a 20 week anomaly scan.
• To diagnose early miscariage. Unfortunately, in 2% of women who attend for a nuchal scan it is found that the fetus has died, often several weeks before and without any warning. Couples will receive full counselling as to the possible causes of this problem and the options for subsequent measures that may be necessary.
• To assess the chance of Down’s syndrome and other chromosomal abnormalities. Each woman will be given an estimate of her individual chance for this pregnancy. This is calculated by taking into account the age of the mother, measurement of two hormones in the mothers blood and the scan findings of nuchal translucency thickness, nasal bone, blood flow through the fetal heart and ductus venosus and fetal abnormalitites. Parents will receive full counselling concerning the significance of these chances and the various options for further investigations including invasive testing or the Harmony test

This is a detailed scan at 20-24 weeks of pregnancy.

During the scan we examine each part of the fetal body, determine the position of the placenta, assess the amount of amniotic fluid, and measure fetal growth. Special attention is paid to the brain, face, spine, heart, stomach, bowel, kidneys and limbs.

If any abnormalities are detected the significance of the findings will be discussed and the couple will be given the opportunity to have further counselling with Professor Nicolaides.

During the nuchal scan (11-13 weeks), the anomaly scan (20-24 weeks) and wellbeing scan (30-34 weeks) we routinely examine the fetal heart and connecting blood vessels.

A specialist examination of the fetal heart is recommended for:

• Women with family history of congenital heart abnormalities, those with diabetes mellitus and those taking antiepileptic drugs
• Fetuses with suspected heart defect and those with increased nuchal translucency or certain non-cardiac abnormalities detected during the routine scans

Specialist fetal heart scans at the Fetal Medicine Centre are carried out by Professor Julene Carvalho, who is a Consultant in Fetal and Paediatric Cardiology at the Royal Brompton Hospital. The scans are usually performed from 18 weeks of gestation, but can be undertaken from as early as 13 weeks if necessary. If an abnormality is found, a detailed explanation of the problem and the outlook for the baby will be provided to the parents and a plan for the subsequent management of the pregnancy will be discussed.

This is a transvaginal scan to measure the length of the cervix.

It is recommended in women at high risk for preterm birth, including multiple pregnancies, those with a previous preterm birth, abnormalities of the uterus or previous cervical surgery.

This examination is usually carried out at the time of the anomaly scan but in women with previous preterm birth it may be necessary to perform a series of scans starting from 16 weeks.

This ultrasound scan is usually carried at about 32 weeks of pregnancy.

Some obstetricians advise that this scan is offered to all women. Others reserve such scans for those women who have had previous complications of pregnancy such as pre-eclampsia, growth restriction, diabetes, stillbirth, and for those women who develop a problem during the course of their current pregnancy.

This scan aims to determine the growth and health of the fetus by:

• Measurement of the size of the fetal head, abdomen and thigh bone and calculation of an estimate of fetal weight
• Examination of the movements of the fetus
• Evaluation of the placental position and appearance
• Measurement of the amount of amniotic fluid
• Assessment of blood flow to the placenta and fetus by colour Doppler ultrasound