An ultrasound scan is a painless test that uses sound waves to create images of organs and structures inside the body. Unlike, X-ray, ultrasound scan does not create any radiation and thus is safe for pregnancy if used properly.
What is routine morphology scan?
Fetal structural abnormality would present at 2-3 in 100 pregnancy, risk various with maternal age and background history. Routine morphology scan is a screening test that should be done in all pregnant.
Why routine morphology scan has to be done at around 20 weeks?
The fetal structure is not well visualized on ultrasound scan if the gestation is too small. The fetal bone would obscure the view if the gestation is too advanced.
Procedure of routine morphology scan It would be done trans-abdominally. No restraint from drinking or urination is required. During the procedure, you would lie on the bed, small amount of aqua jelly would be applied on the abdomen for better contact between the ultrasound probe and the skin. The probe would be moved throughout your abdomen to get images of fetus. Unlike the routine ultrasound checkup, it takes longer for the routine morphology scan. In some situation, due to the unfavorable fetal position, you may need to be rescanned some time later or even reschedule the other date.
How is the accuracy of mid-pregnancy routine morphology scan? Routine morphology scan including examinations of fetal skull, brain, eye socket, lip, spine, heart, lung, diaphragm, stomach, kidney, bladder, abdomen, cord, limbs and external genitalia. There is limitation of ultrasound scan and therefore a normal routine morphology scan report does not mean baby does not have structural abnormality. The functional problem (e.g. mental problem, intelligence, visual or auditory ability etc); subtle structural abnormality (eg cardiac septal defect) or some features that is not able to be identified on ultrasound (eg imperforated anus, some Down’s syndrome etc) cannot be diagnosed on routine morphology scan. Some abnormalities may develop in late pregnancy eg hydrocephalus, bowel obstruction, achondroplasia. Thick maternal abdominal wall, reduced in liquor volume or unfavorable fetal position also affect the accuracy of ultrasound scan. Overall, routine morphology scan at mid pregnancy can diagnose 80% of severe congenital structural abnormality.
What to do if abnormality shown on routine morphology scan? In case fetal abnormality is identified, the obstetrician would monitor the condition and give appropriate counselling. Depends on the situation, he/she may contact the related professional eg paediatrician for joint care. If the condition is lethal, parents can decide for termination of pregnancy before 24 weeks of gestation.
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