Routine prenatal screening tests
Many screening tests are used routinely in pregnancy to assess the health of the mother and baby. Screening includes, for example, tests for maternal diabetes and infections, ultrasounds in second and sometimes third trimester to assess fetal growth and placental placement, and blood tests for iron levels.
Screening for chromosome and structural anomalies
Optional screening tests are also available to identify pregnancies at increased risk of chromosome anomalies such as trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), trisomy 13 (Patau syndrome) and some structural anomalies such as neural tube defects (including spina bifida).
Prenatal screening tests for chromosome and structural anomalies include:
- Combined first-trimester screening. This test combines information from ultrasound (nuchal translucency) and maternal serum markers to calculate risks for trisomies 21, 18 and 13.
- Non-invasive prenatal testing (NIPT, also known as cell-free DNA screening). This can be performed any time from 10 weeks gestation and examines fetal DNA in a maternal blood to provide a risk assessment for the common trisomies (and sometimes for sex chromosome anomalies such as Turner syndrome and Klinefelter syndrome).
- Second-trimester maternal serum screening. This is a stand-alone blood test that screens for trisomies 21 and 18, as well as neural tube defects, including spina bifida.
Screening tests do not diagnose these conditions; they only identify women at increased risk. Guidelines produced by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists recommend that all women are advised of the availability of prenatal screening tests at pre-pregnancy counselling or as early as possible in the pregnancy. Out-of-pocket costs for these tests vary.
High risk results
Women with a highrisk screening result should have access to genetic counselling services for support. They may choose to proceed with diagnostic tests such as chorionic villus sampling or amniocentesis to confirm whether the baby is definitely affected by the condition in question.
Participation is voluntary
Participation in prenatal screening is voluntary. Healthcare providers should support each woman to make an informed choice about whether to have the tests or not.