Routine third trimester screening tests include a full blood count and blood group and antibodies, done at approximately 34 – 36 weeks gestation.
If you are rhesus negative then this test would generally be done at 34 weeks as you will require a prophylactic anti-D injection at this time.
The full blood count looks at your haemoglobin level and platelet level. If the haemoglobin level is reduced then you may require iron studies as well.
There are other third trimester screening tests that may be done which are not routine.
Firstly, you may require an ultrasound scan to check on fetal growth and wellbeing or placental location.
Another common test which is not routine is the low vaginal swab for GBS carriage. This test is generally done in those who are planning a vaginal delivery.
If group B streptococcus (GBS) is detected then you will require prophylactic antibiotics in labour to protect your baby against infection.