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The gestational age should be 17 weeks 6 days to 21 weeks 6 days as the ideal.
There are no absolute contraindications.
There are no relative contraindications.
There are no adverse effects. Medical ultrasound has been in use since 1950. There is no evidence in the medical literature to show any biological or hazardous effects to the foetus. It is a test that has no ionising radiation.
No specific post-procedural care is required.
Foetal magnetic resonance imaging (MRI) might be used to confirm abnormalities seen on ultrasound after 21 weeks gestation. MRI is not a screening examination and most MRI facilities do not offer this service, as it is highly specialised and usually carried out in conjunction with a comprehensive counselling and general foetal diagnostic service.
An obstetrician will usually be guided by a maternal foetal medicine specialist clinic or geneticist regarding the appropriateness of a referral for MRI. MRI is used to clarify abnormalities that are strongly suspected on ultrasound of the foetus, at or after 21 weeks’ gestation if other testing, such as amniocentesis and blood testing, fails to reveal a chromosomal abnormality that would explain the abnormal findings.
There is a reduction in the sensitivity of ultrasound for the detection of foetal abnormalities in obese patients, as the probe is at a greater distance from the foetus.
It might not be possible to see all the foetal structures in multiple pregnancies. Patients might be asked to return on another day to complete the examination when the foetuses might lie in a more optimal scanning position.
Page last modified on 29/3/2017.
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RANZCR® intends by this statement to exclude liability for any such opinions, advices or information. The content of this publication is not intended as a substitute for medical advice. It is designed to support, not replace, the relationship that exists between a patient and his/her doctor. Some of the tests and procedures included in this publication may not be available at all radiology providers.
RANZCR® recommends that any specific questions regarding any procedure be discussed with a person's family doctor or medical specialist. Whilst every effort is made to ensure the accuracy of the information contained in this publication, RANZCR®, its Board, officers and employees assume no responsibility for its content, use, or interpretation. Each person should rely on their own inquires before making decisions that touch their own interests.