Tests During Pregnancy

First Trimester Tests (1 - 12 Weeks)

First Trimester Screening Test (FTS)

Trisomy 21 (Down’s syndrome, Trisomy 18 (Edward syndrome) or Trisomy 13 (Patau syndrome) risk is calculated by using a mother’s age, the level of certain placental hormones (PAPP-A and BHCG) and the measurement of a space behind the neck of the fetus (nuchal translucency).  The blood test is done between 10 and 13 weeks and ultrasound between 12 and 14 weeks.  If the result comes back as high risk, a chorionic villus biopsy or amniocentesis is needed to make a diagnosis. 

Non-Invasive Pre-Natal Testing (NIPT)

Trisomy 21 (Down’s syndrome, Trisomy 18 (Edward syndrome) or Trisomy 13 (Patau syndrome) is screened for by analysing free DNA  fragments in the maternal circulation. A blood test is taken after 10 weeks and cell-free DNA from the mother, the placenta and the babying in the maternal blood is isolated and the risk for the above trisomies calculated. If the result comes back as high risk, a chorionic villus biopsy or amniocentesis is needed to make a diagnosis. It is a better but more expensive test than an FTS and can also test for other genetic abnormalities and the sex of the baby.  It takes around a week for the results to return. 

Chorionic Villus Biopsy (CVS)

With a CVS a small amount of placental tissue is obtained for genetic testing.  It can be done after 11 weeks gestation.  

Amniocentesis

With an amniocentesis amniotic fluid is taken from the fetus for genetic testing. A  needle is passed through the abdominal wall into the sac surrounding the fetus and a small amount of fluid aspirated.  It is usually done after 15 weeks of gestation.

Second Trimester Tests (13 - 28 Weeks)

Anatomy scan

An anatomy ultrasound scan is done between 19 to 20 weeks. This ultrasound scan looks at the baby in great detail.  They look in detail at the spine, brain, heart,  kidneys, placenta, etc.  They also assess the length of the cervix to reduce the risk of preterm delivery.

Third Trimester Tests (29-41 weeks)

Group B Streptococcus (GBS)

We recommend Group B Streptococcus(GBS) swabs at 36 weeks for all women who plan to have a vaginal birth.  These swabs are taken from the vagina and rectum and women who test positive are prescribed antibiotics in labour to prevent the transfer of this bacterium to the baby.

GBS is normally found in the bowel of adults but it comes and goes. At any given time  20% of people carry it.  So if a mother carries it at the time of the birth of her baby, she may pass it on to her baby.  Newborn babies have very little resistance against GBS and can get very sick from it very quickly.  Testing for and treating women who carry GBS reduces the risk of babies getting a GBS infection. 

Glucose Tolerance Test (GTT)

A GTT is a blood test that is routinely done on all pregnant women (unless previously diagnosed with diabetes) between 24 and 28 weeks of pregnancy.   Women have to fast overnight, the next morning a fasting blood glucose level is taken followed by a 75g glucose drink.  More blood is taken at the one and the 2-hour mark.  It is done to rule out/diagnose gestational diabetes (GDM). 

Women at high risk of gestational diabetes eg with previous GDM, over 40 years of age, a family history of diabetes, BMI >35, previous baby bigger than 4500g, Polycystic Ovarian Syndrome, BMI over 35 and ethnic group other than European should also get a GTT in the first trimester.   

Electronic Fetal Monitoring (EFM) or CTG

A CTG (cardiotocograph) is an electronic instrument that is used to monitor the heart rate of a fetus (a baby in utero).  We use it where there is a risk that the placental function may deteriorate which in turn will affect the fetus.  The heart rate is picked up with a special ultrasound probe and recorded on a piece of paper.  By looking for specific features we can tell if the fetus is well and it can also reassure us the fetus well for the next 3 days. CTGs can also be used to monitor the fetus in labour.  CTG is commonly used in women with diabetes, for growth restriction in the fetus, high blood pressure or where there is reduced fetal movements.