Q & A With Dr. Uday Thanawala: The Necessary Tests At Different Stages Of Pregnancy

As you step into motherhood, your and your baby’s health must be your first priority. Dr. Uday Thanawala, a leading obstetrician and gynaecologist, advises on the tests that must be taken at different stages of pregnancy.

Tests during the first trimester (first 12 weeks)

a. Haemoglobin (Hb), Complete Blood Count (CBC):

Having a low Hb and being anaemic in pregnancy is highly avoidable as your Hb should be above 11gm%. Being anaemic makes you lethargic. Less iron can adversely affect your baby too, since iron is needed for proper brain development of your child.
Blood count is done to make sure other blood parameters like platelets are normal.

b. Blood Sugar (Gestational Diabetes):

Do a 75 gms glucose challenge test. Irrespective of fasting (it is difficult to fast when you are pregnant), just take 75 gms of glucose with half a glass of water and give a blood sample for blood glucose exactly after 2 hours. Your blood sugar should be less than 140mg%.

c. Thyroid screen:

TSH (Thyroid Stimulating Hormone) is the test to be done and the value in the first trimester should be around or below 2.5.

d. Infection screen:

Infection status for HIV, Hepatitis B and C must be checked. We repeat these during pregnancy, even though they have been carried out before pregnancy. This is critical. If HIV or, HBsAg (Hepatitis B) is positive, there are measures available to treat so that transmission of infection from the mother to the child can be prevented timely.

e. Thalassemia status:

This can be done if the report is not known through a test prior to pregnancy.

f. Urine routine: 

Sometimes there are bacteria present in urine and cause harm to pregnancy.

At 11-12.4 weeks:

An ultrasonically is certainly recommended at this gestation to rule out defects in the fetus and to measure Nuchal Thickness (NT) (Skin fold behind the neck). This is a specialized scan and better to get it done from a reliable imaging center.

Screening for chromosomal anomalies like Down Syndrome-
A biochemical screening test known as a double marker is available and should be ideally done along with the NT scan described above.
Results of the NT scan, double marker test, age and weight are all fed into a computer software to give you your personalized risk of having a Downs baby.
If this comes as low risk, there is no need for further testing. If it comes as high risk, typically an invasive test like CVS (Chorionic Villus Sampling) is recommended.

At 16-20 weeks:

Screening for chromosomal defects – A triple marker or quadruple marker blood test can be offered, if double marker and NT scan not done earlier. Sensitivity is lesser than the results of the first trimester screening.

At 18-20 weeks:

Anomaly scan is a detailed scan of the foetus to rule out structural defects in the foetus.

At 24-26 weeks:

Blood tests need to be repeated – Hb, CBC – Blood volume increases thus, Hb can drop so must test again now.
75 Gram Glucose Challenge test – This test is a must now because a fair number develop gestational diabetes now. (Sugar could have been normal earlier). Routine Urine test follows.

32 weeks

Ultrasound Scanning – to monitor baby’s growth
Bloods – Nowadays repeating Hb, CBC, Sugar and urine tests is recommended – However, still many take only Hb, if required. Sugar test is repeated, if some signs like extra amniotic fluid develops. 

36 weeks and beyond

Investigations are individualized. You may require further scans for monitoring growth, Amniotic fluid and blood flow (Doppler Studies) to the baby.
NST (Non-stress test) – a test to check baby’s heart rate in response to movement may be ordered.