Congenital Abnormalities And Chromosomal Defects

Congenital Abnormalities And Chromosomal Defects

Between 9-10 weeks

Ultrasound scan confirming absence of structural defects like bowel protruding through abdominal wall defect (omphalocele) and general appearance of the fetus then proceed to

Non-invasive prenatal testing (NIPT) - this uses cell free DNA collected from the mother's blood to detect chromosomal abnormalities with a 99% detection rate for Down's syndrome and ascertain the baby's sex as early as 9-10 weeks gestation. In the event of NIPT abnormalities mother's are advised to have chorionic villus sampling (CVS) which is an invasive test whereby a biopsy is taken from the placenta to check further for chromosomal abnormalities particularly aneuploidy.

Combined test 11 - 13 weeks

This is less accurate than NIPT and involves ultrasound scan and blood tests from the mother. the scan is to check for nuchal translucency (NT) which is the thickness of skin fold behind the baby's neck.

12 - 14 weeks

At this stage all is expected to be normal, however, definitive problems with NIPT or combined test might indicate the need for amniocentesis which is an invasive test like CVS.

20 - 22 weeks

Anatomy scan is performed to look in minute detail at structure of the baby and rule out birth defects in addition to see the size, growth, weight and baby's gender.

What are the risk factors?

  • Mother's age above 31 years
  • Previous history of fetal anomalies
  • Family history
  • Medical conditions such as diabetes, problems related to the mother taking medication

32 - 34 weeks

Growth ultrasound scan is performed in addition to routine physical examination. An account will be given with regard to attendance of antenatal classes in teaching newly pregnant women how to cope with the last four weeks of pregnancy, how labour starts, pain relief methods and breastfeeding.

36 - 38 weeks and until delivery

Further and final growth ultrasound scan, examination of the cervix to determine if labour is imminent or not and baby's head engagement. Check for group B streptococcus (GBS) this is performed by taking a swab from the birth canal for laboratory test about this specific type of bacteria which can require antibiotic treatment during labour if positive.



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