Blood tests during pregnancy of second trimester
Tests & Procedures, Women

Blood Tests To Be Done During Second Trimester of Pregnancy

Blood tests or any other investigations done during pregnancy are advised on the basis of an elaborate maternal case history as a means to ensure that the pregnancy is smooth and uneventful.

Blood tests done during pregnancy not only help in early detection a problem but also provide valuable information regarding the course of pregnancy.

Second Trimester Of Pregnancy

The duration of the second trimester is 13-28 weeks. New features of pregnancy can be observed during the second trimester. These include:

  • Progressive enlargement of the lower abdomen by the growing fetus
  • Quickening (feeling of life) – The perception of active fetal movements by the pregnant woman. These provide positive evidence of a live fetus.
  • Chloasma – Pigmentation over the cheeks and forehead. It can be noticed at about 24th week of pregnancy
  • Breast Changes – Breasts enlarge further with prominent veins under the skin, Montgomery’s tubercles and a variable degree of the stria may become visible.
  • Linea Nigra – A linear pigmented zone extending from the lower abdomen to the midpoint at end of ribs.
  • Stria – Also called stretch marks, pink or white may become visible
  • Fetal Heart Sounds (FHS) – Is the most conclusive sign of an active pregnancy and a live fetus.
  • Vaginal Changes – Bluish discolouration of the vulva, cervix, and vagina

Blood Tests During Pregnancy Second Trimester

Blood tests during pregnancy are conducted as a part of antenatal or prenatal care. Some blood tests done during the second trimester of pregnancy are

1. Blood Group And Rh Factor

Test for blood group and Rh factor is done not only for the other but also for the father. If the Rh factor of parents do not match (for example, the mother is Rh positive and the father is Rh negative), the mother may develop antibodies which can be harmful to the fetus.


No specific preparation such as fasting is required for blood group testing.


Blood group and Rh factor testing requires the collection of the venous blood sample.

Results and Interpretation

Blood group may be A, B, O or AB. Rh factor may be positive or negative.

2. Complete Blood Count (CBC)

CBC test may have to be done if it has not been done during the first trimester. A complete blood count helps to understand the nutritional status of the mother, presence or absence of anemia. It also gives a general idea regarding the blood cell indices.


Testing for a complete blood count does not require any specific preparation.


Testing for a complete blood count requires the collection of the venous blood sample to be sent to the laboratory for testing.

Results And Interpretation

Some valuable CBC indices are given in the table below with their normal values. Any blood counts below or above the normal reference range is considered to be abnormal.

Sr. No. CBC indices Normal values
1. Hemoglobin 12 – 14 gram%
2. Red blood cells (RBC) 2.5 – 5.5 million/
3. White blood cells (WBC) 5000 – 10000/
4. Platelets 1.5L – 4.5L/

3. Multiple Marker Test

This test is done specifically during the second trimester of pregnancy. This test may also be combined along with other screening tests during the first trimester and is then called the integrated screening test

Screening Tests

These blood tests are done in order to screen for illnesses common in India such as hepatitis B, HIV, syphilis, rubella, and chicken pox. Screening tests not only help in early diagnosis but can also help in providing immediate care and treatment for any of these illnesses during pregnancy.


Screening tests for infections do not require any specific preparation.


Blood tests for screening infections during pregnancy is done by a collection of a venous blood sample which is then sent to the laboratory for testing.

Results And Interpretation

Screening tests for infections may be termed positive or negative based on the presence or absence of infections.

[ReadBlood Tests That Requires Fasting ]

4. Multiple Marker Test Helps To Detect The Following

  • Neural Tube Defects (Birth Defect Of The Brain or Spinal Cord) – Spina bifida and anencephaly being the commonest neural tube defects)
  • Chromosomal Abnormalities – Such as trisomy 18 or Down’s syndrome


Multiple marker test or the integrated screening test does not require any kind of preparation.


Multiple marker test requires the collection of a blood sample from the vein which is then sent to the laboratory for testing.

Results And Interpretation

The test may or may not be combined with other radiological techniques to definitively diagnose neural tube defects. Results of the test will be interpreted accordingly.

5. Glucose Screening

This test is done specifically to detect gestational diabetes mellitus in pregnant women. Blood glucose testing is done at 24-28 weeks of pregnancy, but may also be done earlier if the pregnant woman is at high risk for developing gestational diabetes mellitus.

Blood glucose screening is usually done by testing for periods of fasting and post-prandial (2 hours after meals).


Testing for fasting blood glucose levels requires fasting for 12 hours before the blood sample can be collected and sent for laboratory investigation.

Post-prandial blood glucose test does not require fasting. It is done 2 hours after meals.


Blood glucose levels testing requires the collection of a blood sample from a vein or it can also be done by pricking the index finger with a lancet and using glucose test strips for quicker results.

Results and interpretation

Normal values for blood glucose levels are:

  • Blood glucose (fasting): 80 – 120 mg/dl
  • Blood glucose (post-prandial): 120 – 140 mg/dl

Blood tests during the second trimester of pregnancy are often done along with other radiological investigations such as:

  • Routine Sonography – This is done to obtain a detailed report of fetal anatomy, location of placenta and integrity of the cervical canal. Gestational age can also be understood by means of sonography during the second trimester of pregnancy.
  • Magnetic Resonance Imaging (MRI) – MRI may have to be done to ascertain fetal anatomy in the presence of some skeletal or chromosomal abnormalities.

Since blood tests advised during pregnancy can cause worry and panic for any pregnant woman, it is important to receive complete information about the tests advised and reasons why they have been advised to you.