First Trimester Investigations – why are they essential ?

I cannot explain how important First trimester investigations are in preventing complications later on in the pregnancy. In this discussion you will learn why and what are the 10 essential tests that one must undergo in the first three months of pregnancy.

Pregnancy is the most wonderful news a woman, a couple can receive. But with great news comes great responsibility. Responsibility of brining a healthy child into this world. How do we do that? If the couple has had a preconception counseling done, then we know that both have been screened for basic disorders and the lady was primed for a healthy and safe pregnancy. However, if the couple did not have any such consult or investigations, then an unhealthy environment may prevail inside of her.

Why is it so important to get First Trimester investigations early in pregnancy? Why can’t we do these tests once the pregnancy settles down?

When your pregnancy first gets detected after a missed period, the embryo or forming baby is already about 2 weeks old. The first 3 months of pregnancy is the time of what we call ‘organogenesis’ that is when most of the vital organs of the baby are forming. Common sense thus states that if there is something unhealthy in your body environment at this time, it can negatively and permanently affect your child.

Secondly, that unfriendly environment can also increase the chances of miscarriage.

Last but not the least, certain deficiencies in early pregnancy can also increase the chances of complications for the mother during late pregnancy.

Let’s discuss the 10 First Trimester Investigations which I feel are essential once your pregnancy has been confirmed with a positive beta hCG:

Hemoglobin Test (Hb):

It’s very important that you start pregnancy with a good Hb level. We know that the role of Hb is to carry oxygen to the various parts of the body and thus with its deficiency, the small embryo growing inside of you can be deprived of good oxygen supply. Since the blood volume is set to increase to about one and half times in pregnancy owing to greater needs for the mother as well as her baby, there is obviously going to be more Hb requiring to be produced. Although not mandatory, it makes sense to also check for Ferritin levels. Ferritin gives us a clue about the iron stores. Iron is an essential ingredient in the manufacture of Hb. Even if the Hb levels are normal but the iron stores are low, we know that in due course of time, when iron stores are depleted, the Hb levels will start to fall.

There are some women who genetically have low Hb. Thalassemia is the most common blood genetic disorder in our country. It might be of major variety or minor variety. If major, then it’s incompatible with life unless the person undergoes repeated blood transfusions, sometimes even weekly. In the minor variety, the only complaint the person will have is that the Hb always keeps low, maybe around 10 or so. The person will go through life without a problem. Trouble starts when two people who both have thalassemia minor get married. There is a 25 % chance of having a child with the major variant that is incompatible with life. I once had a couple who had a love marriage and they both only discovered during pregnancy that both had the minor variant. Luckily for them, the child escaped with a minor variety of thalassemia. A simple blood test can tell us about thalassemia, and it makes every sense to test for it during early pregnancy itself.

Blood group.

We all know it’s important to know the blood group but why is it important to know about it in the first 3 months itself? If the woman has an Rh -ve blood group and her husband has a positive one, then the woman will require some injections around the 6th month of pregnancy. She will require the same injection in the 1st month too in case she has any spotting or bleeding at that time. In case she doesn’t get the injection because the blood group wasn’t tested then the future pregnancies could get complicated.

Blood sugars:

I can’t emphasize enough the importance, not only of testing sugars in the first 3 months of pregnancy but also of doing it the right way. I won’t elaborate this here since the subject is so important that it deserves a separate episode by itself on Gestational diabetes.

Thyroid abnormalities:

Any disorder of the thyroid gland can result in miscarriages in the first 3 months, improper brain development in the baby and abnormal weight gain or loss for the mother. Thus, it makes sense to find out the thyroid glad status at the earliest.

  • This is exactly when although in non-pregnant states, if one has a TSH value below 10 milli IU/ L and doesn’t have symptoms, he or she does not need treatment.
  • But if the same lady is trying to conceive or is pregnant, the value must necessarily be between 2.5 and 3.5 m IU/L.

Vitamin D.

One study was done in rural north India… and mind you in rural India, exposure to sunlight is plenty, 88.6% of adolescent girls, 74% of pregnant women and 94% of babies born to such mothers had vitamin D deficiency. We know vitamin D is important for strong bones but how is it important in pregnancy and that too in the first 3 months?

Increased risk of high blood pressure in pregnancy, higher risk of gestational diabetes, 4 fold increase in cesarean section, vaginal infections, low birth weight of the baby, convulsions in the newborn, impaired growth and bone development in the fetus, increased chances of asthma, respiratory infections and low immunity in the child…..whew……all of it because of Vit D deficiency not being corrected in the first 3 months of pregnancy. That’s how important it is and that why its on my list of essential first trimester investigations

Check for Rubella status.

Now vaccination for the Rubella virus along with Measles and mumps is given after birth and women of childbearing age probably would be immune. Yet we do find many women not to be immune and if such a woman gets pregnant and if this virus were to affect her during pregnancy, the child could be born with serious congenital defects. Ideally, we test for it during the pre-conception time but if it hasn’t been checked then, it makes sense to do the test right away in pregnancy.

Urine routine and culture.

I don’t know why but this simple test is often ignored despite enough evidence for its testing. There is something called asymptomatic bacteriuria which happens commonly in pregnancy, which means bacteria being present in urine but the patient showing no symptoms. Thus, if one were to base the test only on symptoms, one would miss. This urine infection can, of course, become more severe and cause pain and discomfort but even without symptoms, it can cause miscarriages, preterm delivery and low birth weight of the baby.

Ultrasound at 6 weeks of pregnancy.

Ultrasound in one of the most essential first trimester investigations to help confirm a viable pregnancy.

A vaginal scan done 6 weeks from the first day of the last menstrual period has 3 functions:

  1. To document that the pregnancy is safe, and the baby’s heartbeat can be seen
  2. To show that the bay is inside the uterus and not anywhere else causing what we call as Ectopic pregnancy
  3. Last but not least it also helps to accurately date the duration of pregnancy esp. in women with irregular periods.

Ultrasound is not harmful in any way and neither is the act of doing it vaginally. They use only sound waves and are thus not harmful at all to the baby

Extended First Trimester screen.

This involves doing an ultrasound between 11 to 13 weeks of pregnancy and a blood test along with it. It is a very important landmark and this test should not be missed. It gives a few of these insights:

It tells us the probability of the child having Downs’s syndrome, which is probably the most common cause of mental retardation and happens because of a genetic defect.

A good sonologist using an excellent machine can already start telling you if the baby’s heart and brain are going to be normal…. Although the scan is better done between and 18 and 22 weeks but even at this early stage one can get hints.

Through the associated blood test, we can also predict what are the chances of this mother developing high blood pressure later in pregnancy and if indeed the risk comes high, we have ways and means of mitigating this risk and ensuring a safe pregnancy.

So, you see while on one hand, you may feel that this is a normal natural conception for you and why is the doctor asking for so many tests, there is a strong reason behind that decision. The first trimester investigations will ensure you have a smoother and hopefully uncomplicated pregnancy and give your child the healthy development and safe entry into this world which he or she deserves.

Also read:

Vaginal bleeding during pregnancy first trimester


Hard facts about constipation during pregnancy

Do look up:


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