This information is for you if your baby's head, tummy or thigh bone has measured small on the fetal anomaly scan
This information is for you if your baby’s head, tummy or thigh bone has measured small on the fetal anomaly scan
This information is for you if a small measurement is the only unexpected finding on your fetal anomaly scan. Your midwife or hospital doctor (obstetrician) will explain in more detail which tests and care you might need. Every pregnant woman in Wales is offered a fetal anomaly scan when they are between 18 and 20 weeks pregnant.
The scan checks whether your baby appears to be developing as expected. This means it may show unexpected findings, such as a small measurement, and you may be offered further tests.
Contents
― What is a small measurement?
― What will happen next?
― What tests may I be offered?
― Ultrasound scans
― Blood test for infections
― MRI
― Genetic testing
― Further information
― Smoking
What is a small measurement?
During the fetal anomaly scan, the size of your baby’s head, tummy (abdomen) and thigh bone (femur) are measured to check how they are growing. The sonographer carrying out your scan will check whether these measurements are within the expected range. If any measurements are smaller than expected, they will tell you which measurement is small.
In most cases when a small measurement is the only unexpected finding on the fetal anomaly scan, your baby will grow and develop as expected.
The list below shows some conditions and outcomes that have been found in babies with a small measurement. The doctor or midwife will discuss with you which of these findings may be associated with your baby’s small measurement.
- Babies born smaller than expected
- Babies born too early
- Babies that have (or have had) a viral infection
- A medical condition you have which may affect your baby’s growth
- Babies that have a genetic condition
- An increased chance of stillbirth
What will happen next?
The doctor or midwife will explain what care you will be offered. They will explain more about the small measurement and discuss the tests you can have, how they are done and when you can have them.
They will review the care you have received in your pregnancy so far. They will also review the screening tests you have had and your scan findings. They will explain more about the scan findings and how they may be linked to other conditions, and about further tests you may be offered.
Some women decide not to have any further tests. The doctor or midwife will support whatever choice you make. You can ask them questions that are important to you. You may want to have another appointment to ask further questions. You might want your partner or another person to come with you for support. You may want more time to think before you decide what to do next. Depending on how small your baby’s measurement is, or the results of your tests, you may be referred to a fetal medicine specialist for a further review and to plan any follow-up care. This appointment may be at a different hospital.
What tests may I be offered?
This will depend on:
- which measurement is small, and
- how small the measurement is.
You may be offered another scan to monitor the measurement. You may also be offered regular scans during the rest of your pregnancy to check the growth of your baby.
You may be offered a blood test to see if you have had a recent infection, such as cytomegalovirus (CMV), syphilis, rubella or toxoplasmosis. If the blood test shows you have had a recent infection, the virus may have passed across the placenta (afterbirth) and infected your baby, which may cause harm.
If your blood test shows that you have had one of these infections, you may be offered an amniocentesis to check if it has passed to your baby. Antenatal Screening Wales has more information about amniocentesis on their web page ‘This information is for you if you have been offered further tests for suspected chromosomal or genetic conditions’. Your midwife can give you a copy of this.
If the hospital offers to refer you to a fetal medicine specialist, the specialist may discuss further tests, such as the following.
If your baby’s head measures small at your anomaly scan you may be offered an MRI scan later in your pregnancy to check how their brain is developing.
You may be offered an amniocentesis to test the amniotic fluid (the fluid that surrounds the baby in the womb) to see if your baby has a genetic condition.
You may want to think about what you might do if the test results show your baby has a genetic condition. Some women will want to prepare themselves for the birth knowing that their baby has a condition. Other women may decide to end the pregnancy.
You can get more information about amniocentesis on the Antenatal Screening Wales web page ‘This information is for you if you have been offered further tests for suspected chromosomal or genetic conditions’. Your midwife can give you a copy of this.
You can get more general information from the hospital doctor or the midwife who specialises in antenatal screening.
NHS 111 Wales
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