Prenatal Blood Tests | HealthReview

Why Prenatal Blood Tests Matter

Prenatal blood tests help monitor your health and your baby's development, screening for conditions that could affect the pregnancy if untreated.

First Trimester Tests

Test	Purpose
Blood type & Rh factor	Identifies blood type and Rh compatibility risk
CBC	Checks for anaemia and infection
Rubella & Varicella immunity	Confirms immunity to these infections
Hepatitis B & C, HIV, Syphilis	Screens for infections that can affect the baby
Thyroid (TSH)	Untreated thyroid issues can affect pregnancy
First trimester screening (PAPP-A, hCG)	Assesses risk of chromosomal conditions

Second Trimester Tests

Test	Purpose
Glucose Challenge Test	Screens for gestational diabetes (24–28 weeks)
Quad screen	Assesses risk of chromosomal and neural tube conditions
CBC (repeat)	Monitors for anaemia as pregnancy progresses

Third Trimester Tests

Test	Purpose
Group B Strep culture	Screens for bacteria that can affect the baby during delivery (35–37 weeks)
CBC	Final check before delivery
Repeat infection screening	If risk factors are present

Frequently Asked Questions

What blood tests are done early in pregnancy?

Early antenatal tests typically include blood group and rhesus status, full blood count for anaemia, and screening for infections such as HIV, hepatitis B, and syphilis to protect mother and baby.

What is screening for Down's syndrome?

Combined screening uses a blood test with a nuchal-translucency ultrasound to estimate risk; non-invasive prenatal testing (NIPT) offers a more accurate blood-based option where available.

Are prenatal blood tests compulsory?

No. Antenatal screening is offered and recommended, but you can choose which tests to accept after discussing the benefits and implications with your midwife or doctor.

How antenatal testing is scheduled

Antenatal tests follow a broadly standard timetable. At the booking appointment (ideally before 10 weeks) blood is taken for blood group and rhesus status, a full blood count to check for anaemia, and screening for infections including HIV, hepatitis B and syphilis. Screening for Down's, Edwards' and Patau's syndromes is discussed and, if accepted, performed between 11 and 14 weeks.

Later in pregnancy, a repeat full blood count and antibody screen is usually taken around 28 weeks, along with an oral glucose tolerance test for those at risk of gestational diabetes. Anti-D is offered at this point to women who are rhesus negative. Every test is optional, and your midwife should explain what each one looks for before you decide.

Prenatal Blood Tests: Complete Pregnancy Testing Guide