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Screening in Pregnancy

From Mediwikis

What is it?

Screening tests in pregnancy aim to detect a disease or condition in its very early stages, where treatment can be offered. The potential benefits of a screening test should outweigh any possible risks from the test. At stages after 18 weeks, the symphysis/fundus height, and blood pressure & proteinuria are screened for

Timetable

Planning

Ideally when a couple are planning to have a baby, they should visit their GP to get information, discuss any lifestyle changes (smoking, food), and start folic acid (400micrograms normally, or 5 mg for high risk women).

Booking

Booking should ideally take place before 10 weeks gestation. See Early Pregnancy for more information.

12 weeks

Dating scan- gestational age, estimate date of delivery, detect multiple pregnancies.

16 weeks

Discuss results of screening, offer further investigation, counseling or treatment if appropriate.

18-20 weeks

Ultrasound scan of child including four chambers of heart and markers for Down's Syndrome

25 weeks

Only undertaken in nulliparous women.

28 weeks

  • Test for anaemia & alloautoantibodies
  • Offer treatment for above

31 weeks

For Nulliparous women only

  • Review results of 28 week tests

34 weeks

  • Review results of 28 week tests
  • Offer specific information regarding labour, birth & caesarean section

36 weeks

  • Screen for abnormal fetal presentation, confirm by ultrasound
  • Offer external cephalic version, where contraindications are not present.

Offer information on breastfeeding, postnatal care of the baby and oneself

38 weeks

Offer information on prolonged pregnancy and induction.

40 weeks

For nulliparous women only

  • Offer further information on prolonged pregnancy

41 weeks

Offer:

  • membrane sweep
  • Induction of labour

42 Weeks

For women who decline induction, provide bi-weekly monitoring

Screening for Down's Syndrome (Trisomy 21)

All pregnant women in every pregnancy should be offered the screening test for trisomies, (this includes Down's syndrome, Edward's syndrome (trisomy 18) and Patau's syndrome (trisomy 13)), though it is their decision on whether they take the tests or not. It is important that women are given all the possible information they might need to make a decision on whether to have the tests and the options for going forwards if they come back positive before the tests are performed. This is a key moment in every pregnancy and one that many mothers are very concerned about and should be dealt with carefully.

The combined test involves a lot of information that is combined to formulate the risk figure it includes:

  • Maternal age
  • PAPPA serum level
  • Beta hCG serum level
  • Nuchal translucency measurement (performed at the viability and dating scan ~11weeks)

The test is 75% sensitive and has a 3% false positive rate in detecting Down's syndrome.

The triple test is another screening test that can be offered to pregnant mothers when screening has to take place after 14weeks (e.g. late booker) or a detailed USS (ultrasound scan) to measure nuchal translucency is not available. The triple test is a blood test that measures the levels of:

  • AFP
  • hCG
  • Oestriol

This test is not as accurate as the combined test which is preferable.