Prenatal Testing: Normal Ranges for Various Tests


As a parent you always wish a healthy life for your baby. I am sure you want to protect your little one. Prenatal tests are some tests which help doctors to protect your baby from deadly diseases and monitor its growth and development. So every pre natal visit should be done and followed. None of the prenatal or postnatal visit should be missed. Here is some information about the tests you may have to go through.

What are pre natal tests actually?

Pre natal tests are various tests done during pregnancy. They are done to monitor the growth and development of your baby. They also help you to detect the abnormalities early, which can help to prepare yourself mentally, physically as well as financially.

Why are tests done?

  1. Growth and development- these tests help you to monitor growth and development of your baby. The anatomical development is checked from time to time. These tests are done in every trimester so that any anatomical or developmental anomalies can be detected and then can be corrected, prevented or managed.
  2. Congenital diseases- congenital diseases are the diseases which are caused to baby due to infection to mother or on their own inside the uterus. These diseases may cause anatomical defects or lifelong physiological problems. Some of the diseases are fragile X syndrome, Tay Sachs syndrome, thalassemia, spinal muscular atrophy, cystic fibrosis, heart diseases etc.
  3. Complication in pregnancy- complicated pregnancy does not necessarily mean any disease. Complicated pregnancy involves high blood pressure of mother, diabetes to mother, more than one foetus, malnourishment, unusually more or less pain, unusual weight gain or late pregnancy. All of these are considered as complications in pregnancy. These pre natal tests help to identify them and act accordingly.
  4. Number of babies– Ultrasound is a routine pre natal test. In first trimester only you will get to know the number of foetus. This helps parents to plan accordingly.
  5. Sex determination– if you are excited about knowing the sex of baby in advance then you can know the sex of baby through pre natal tests. Though in some countries it is illegal to determine the sex of baby.

List of Prenatal tests

prenatal testing

Type of tests

  1. Screening– screening tests are done normally to check mother for any diseases. Some examples of screening tests are
  • Blood tests– to test for various infections like syphilis, hepatitis, toxoplasmosis, cytomegalo virus, rubella virus etc. they are done in areas where women are prone for them.
  • Urine tests– urine tests are done for glucose, protein, excess urea, uric acid or bacteria in urine. They help to check for some common infections during pregnancy.
  • Ultrasound– USG is done for checking the growth and development of baby. It is done when there is risk of any anatomical anomaly to the baby.
  1. Check up– these are tests done for monitoring regular growth of baby. These are not much expensive and also non invasive. Parents should not skip these tests though. I am sure you want to be certain about the health of your baby.
  2. Diagnostic tests– diagnostic test are done to be sure about the disease. They may be invasive, but they are not done until some risk factors are present. Oral glucose tolerance is one such test, when mother has a risk of diabetes then oral glucose tolerance test is done to diagnose gestational diabetes mellitus. Without risk factor these tests are not performed.

Prenatal tests-

Tests done in 1st trimester

a.  Blood tests– blood tests done in first trimester are generally for knowing any pre existing diseases in mother. They detect pre-existing infections. Also if mother is anaemic then it can be known, so that we can start treatment for anaemia well in advance, which will prevent the baby from suffering. Also blood group of mother is checked, this is for two reasons

  • For keeping blood ready in case of post partum haemorrhage. It is a risk factor in complicated pregnancy.
  • If mother is RH negative and father is RH positive then she has to be given a shot of RH immunoglobin to prevent RH incompatibility between mother and child. The immunoglobin is given at 28 weeks and other one after delivery

b.  Glucose tolerance test-it is done for diagnosis of diabetes mellitus. If the women suffered from gestational diabetes in previous pregnancy or her mother or sister has suffered from gestational diabetes then doctors may suggest glucose tolerance test.

c.  Ultrasound– Ultrasound is very useful test done during pregnancy. It is very important to monitor the growth and development of the baby. In first trimester mainly the points which are observed are-

  • Conformation of pregnancy– pregnancy is confirmed by ultra sound in first trimester
  • Size– according to size of embryo the age can be detected. The date of labour can also be predicted. Growth of the baby can be compared with expected growth chart.
  • Position– if there is implantation of embryo in any other place than normal then it can be understood and treated accordingly. It is known as ectopic pregnancy.
  • Multiple gestations– No of embryo’s can be detected. This helps to plan the nutrition of the mother as well as helps the parents to plan their future accordingly.
  • Nuchal translucency- nuchal translucency means checking the accumulation of fluid on the back of the neck. It is done at 11-14 weeks of gestation. If there is fluid accumulation at the back of the neck then there can be higher risk of Down’s syndrome. Thus doctor can treat the condition early and prevent down’s syndrome

d.  Blood pressure– blood pressure is checked from time to time as a basic test of the mother. Blood pressure of the mother is monitored because of the risk of pre eclampsia, eclampsia and gestational hypertension. These are the greatest threat to a mother during pregnancy. All these condition include one primary symptom i.e. increase in blood pressure. Ranges of BP in pregnancy are

  • <140/90 mm of Hg- Normal
  • 140/90-149/99 mm of Hg – mild hypertension
  • 150/100-159/109 mm of Hg – moderate hypertension
  • >160/110 mm of Hg – severe hypertension

e.  Chorionic villa sampling– chorionic villous sampling means checking the samples from the chorionic villas of the embryo. This test is nit done unless needed. It is done only if, there is any history of genetic disease, any sibling is suffering from any genetic disease or if mother has suffered abortion in past due to any genetic condition of baby. Then the sample of chorionic villa is tested for genetic diseases. This test is done early than amniocentesis. It helps us to detect disease early thus we can prepare and prevent disease early.

Tests done in 2nd trimester

a.  Blood tests– in second trimester blood test are done mainly to diagnose certain diseases which have greater chances during pregnancy. Level of protein markers are checked in serum which indicates any abnormality in foetus. Other enzymes like human gonadotropin hormone, genetic makers are also checked. These markers are checked in case of any risk factor present in mother.

b.  Urine test– urine test are done to check glucose and proteins in urine. Results are

  • Presence of glucose- presence of glucose indicated gestational diabetes mellitus. Glucose should not be present in urine.
  • Presence of protein- proteins also should not be present in urine. They indicates problem in functioning of kidney. During pregnancy there are lots of changes in body. Many organs are affected; lots of hormonal changes are caused. Kidneys are at greater risk during pregnancy. So protein levels have to be checked for their normal function.

c.  Amniocentesis- amniocentesis is a specific diagnostic test. Amniotic fluid has foetal cells they can be checked for chromosomal disorders like Down’s syndrome, spina bifida etc. But this is done only if

  • There is family history of genetic disorder
  • Mother is more than 35 years
  • Parents are carrier of any genetic disorder
  • Mother suffered abortion due to any related conditions

d.  Ultrasound– ultra sound in 2nd trimester is again commonly done. It is done to monitor the growth of baby and find any anatomical defects


Tests done in 3rd trimester

a.  Mature amniocentesis– mature amniocentesis is amniocentesis done in 35-37 weeks of pregnancy. It is done to check the development of lungs. Since after birth if lungs are not developed then baby will suffer from hypoxia. This is mainly done in premature babies or babies lagging in development

b. Ultrasound– ultrasound in last trimester is done only when any anatomical anomaly is suspected. And also to know the position of the baby

c.  Group b streptococci– group streptococci is a very common yet dangerous bacteria. It can be transferred to mother or baby if delivery or any procedure is done without maintaining proper sterility. They can also attack mother through any infected person. Hence maintaining hygiene and protecting mother from any potential threat is very important.

d.  Swabbing– swabbing of vagina may be done to avoid any infection during birth. It is done only is suspected cases. Test for cytomegalo virus, rubella, hepatitis b, streptococcus etc. is done.

These were the prenatal test you may have to go through. These tests are very important for the protection of your baby. They will help you to connect with your baby during the pregnancy as well as protect it from any diseases. After all, “prevention is far better than cure”.

Hope this article was of help for all our parents!! Please share your comments/queries/tips with us and help us create a world full of Happy and Healthy Babies!!