Essential Tests During Pregnancy: What Every Expectant Mother Should Know

Author:  Nnenna Chiloli, MBBS, MPH

Medical Reviewer:  Azuka Chinweokwu Ezeike, MBBS, FWACS, FMCOG, MSc (PH)

Highlights

• Essential tests during pregnancy are important because they identify potential health issues early.

• Prenatal tests screen for genetic disorders, infections, and other conditions that may affect the mother and baby.

• First-trimester tests include blood tests, urine tests, ultrasound scans, and genetic screening.

• Second-trimester tests are anatomy scans, glucose screening, and the quadruple test. 

• Third-trimester tests involve Group B Streptococcus screening, repeat blood and urine tests, and ultrasound scans.
• Normal results indicate a healthy pregnancy, while abnormal results may require further testing.
• Prenatal tests enable early detection and prompt treatment, ensuring the best possible outcomes for mother and baby.

Introduction

Pregnancy is a time full of joy, wonder, and a bit of worry. From the first stir you feel to the first time you hear your baby’s heartbeat, each moment is full of both happiness and questions.

Pregnancy is the period when a baby grows inside a woman’s womb or uterus. It causes body changes as women’s bodies change to accommodate the growth of the baby.  The average duration of pregnancy is 40 weeks. It is divided into three stages or segments called trimesters.

Risk identification and prevention are two key steps during pregnancy. To achieve these aims, many lab tests are offered to all pregnant women who attend antenatal care. These tests tell a lot about your health and that of your unborn baby.

One of the key steps in this journey is prenatal (antenatal) testing. These tests are normal, widely recommended, and built for one aim, which is to keep you and your baby from harm. They offer peace of mind when all seems fine, and if there’s a need to look closer, they give health care providers the chance to act early.

Prenatal tests are conducted throughout pregnancy, beginning at the first prenatal appointment and continuing through the second and third trimesters. Most of them are simple and painless procedures, though some, such as certain genetic tests, are more complex.

Some prenatal tests are considered routine, meaning that almost all pregnant women who receive antenatal care undergo them. 

Why Prenatal Tests Matter

Prenatal tests can help identify health problems that could affect you and your baby. They enable the early identification of conditions that could interfere with your baby’s development, as well as prevent or treat issues that may arise during pregnancy, such as infections, gestational diabetes, and hypertension.

The tests can detect abnormal conditions during pregnancy [1].  This is important because spotting potential problems early gives more time to plan [2].  Some conditions are better managed or treated when detected early, so it's beneficial to identify them promptly.

Benefits for the baby,

• Identify treatable health problems that can affect the baby
• Show the baby’s size, sex, age, and position in the uterus
• Help determine whether a baby might have a birth defect, genetic problem, or other conditions.

 Benefits to the mother 

• Helps to determine some diseases in the mother that may worsen or affect the outcome of the pregnancy

Non-Routine Tests for High-Risk Pregnancies

For certain women, particularly those with high-risk pregnancies, additional non-routine tests are advised. The high–risk pregnancies may include women who are;

• Age 35 or older at the time of delivery
• Have had a premature baby
• Have had a baby with a birth defect(especially heart or genetic problems)
• Carrying more than one baby
• Have high blood pressure, diabetes, heart disease, kidney problems, seizures, and many others.
• Have pregestational diabetes 
• Exposed to known substances that affect the normal development of the baby, such as alcohol, tobacco, cigarette smoking, etc
• Exposed to radiation or harmful chemicals
• Have infections such as rubella

Types of Tests During Pregnancy

Although each trimester has its own spot check, they together provide a safety net that helps you and your medical team monitor your baby’s growth, avoid problems, and be ready for a safe delivery.

First Trimester Tests

The first trimester is all about getting to know your pregnancy. On your early visits, your provider will recommend the following tests;

• Blood Tests

The blood tests include the following;

• Blood Type and Rhesus(Rh) factor 

This helps detect if there’s a risk of Rh incompatibility(which can cause problems for the baby’s blood). Rh incompatibility occurs when you are Rh-negative and your baby is Rh-positive. 

The mother's body sees your baby as foreign and builds antibodies against the child’s blood [3]. A Rhesus immunoglobulin injection may be necessary.

• Genotype 

 Blood genotype identifies the type of protein (Haemoglobin) that is in the red blood cells. It checks if you or your partner carries inherited conditions such as sickle cell anaemia.

• Complete Blood Count. 

This checks for low blood count(anaemia) or infection.

• Infectious Disease Screening

This checks for:

• HIV 
• Hepatitis B 
• Syphilis, etc. 

The test ensures early identification and treatment, as well as the implementation of preventive measures against mother-to-child transmission of infection [4].

• Urine Tests

This test checks for sugar, protein, ketones, bacteria, and blood cells. It helps to detect issues like gestational diabetes, preeclampsia, or urinary tract infections.

• Ultrasound scan

Ultrasound is a test that allows your healthcare provider to see into your body without surgery. It uses sound waves to create images of the organs, tissues, and other structures inside your body.

The ultrasound for the first-trimester screen is used for the following;

• To confirm your pregnancy
• To detect multiple pregnancies
• To determine the baby’s age
• To calculate the baby’s due date
• To detect early signs of developmental concerns
• To detect certain chromosomal disorders, such as Down syndrome

• Early genetic screening

This is done in women who are at risk of having babies with abnormalities. It is a non-routine test.Genetic screening (First Trimester Screen) checks for the following:

•  Pregnancy-associated plasma protein-A (PAPP-A),
• Human chorionic gonadotropin 
• Nuchal translucency (Checked with ultrasound)

When abnormal, it indicates the need for other tests like Chorionic villus sampling and amniocentesis.

Second Trimester Tests

• Anatomy scan

This is an ultrasound scan. It’s done at 18 to 22 weeks of pregnancy. It checks the following;

• Baby’s organs and overall growth [5].
• Location of the placenta
• Confirm the number of babies in the womb
• The sex of the baby, if you want
• The baby’s age

• Anomaly scan

This is the use of an ultrasound scan to check your baby’s organs to identify any anomalies, such as;

• Absence of a large part of the brain(anencephaly)
• Failure of the spine to close fully(spina bifida)
• Opening in the upper lip(cleft lip)
• Serious problems in the heart

•  Oral Glucose Tolerance Test (OGTT)

Pregnancy can affect how your body handles sugar by reducing insulin (a substance that regulates blood sugar) action. The reduction in insulin action becomes apparent in the second trimester, and insulin resistance increases as the pregnancy progresses.. 

This means diabetes in pregnancy usually develops in the second or third trimesters, and glucose tolerance may return to normal after delivery [6].

A glucose screening test (OGTT) screens for gestational diabetes, a condition that can affect both you and your baby if not managed. This test is done between the 24th and 28th week of pregnancy.

• Quadruple test

Quadruple test measures the levels of four substances in the pregnant woman’s blood, namely;

• Alpha-fetoprotein,
• Human chorionic gonadotropin 
• Unconjugated estriol
• Inhibin A 

This test assesses the risk of birth defects or chromosomal abnormalities in the unborn baby. It is typically suggested when earlier screening wasn't done.

Third Trimester Tests

These tests help to ensure both you and your baby are ready for a safe delivery.

• Group B Streptococcus screening (GBS)

Group B streptococcus is a bacterium that lives in your vagina or rectum. It can be passed to the baby during childbirth and can cause serious complications.

GBS is a simple swab test that checks for the presence of the bacteria. If identified, antibiotics during labour can prevent the baby from contracting it.

• Repeat tests

Your health care provider may recheck the following tests in the third trimester of pregnancy;

• Blood test. This checks for anaemia and Rhesus antibody if you are Rhesus negative.
• Urine to check for protein or sugar, and signs of infection
• Ultrasound for the baby’s position and growth.

Third trimester ultrasound checks for;

• Baby’s growth
• Amount of amniotic fluid
• Baby’s position
• Placental position
• Placental health

Understanding Test Results

Your doctor would explain the tests to you. A normal result shows that the test didn’t identify any problem.  It means that your pregnancy is not at risk.  For instance, your ultrasound might show your baby is growing well. 

Although normal results don’t entirely ensure a problem-free pregnancy, they suggest that things are going as they should.

An abnormal result does not always mean something is wrong. It is a pointer to more tests or checks. For example, if your blood test shows that your blood count is low, your healthcare provider will do more tests to find the cause and treat it properly.

Conclusion

Essential tests during pregnancy are not just about finding problems. They help you and your healthcare provider work toward the best care. It’s made to keep you and your baby safe and well.

By identifying risks early, healthcare providers can quickly find and treat the condition. It also helps you and your family to prepare for the care your baby might need later.

References

1. Padoan A. Laboratory tests for monitoring physiological pregnancy. Journal of Laboratory and Precision Medicine [Internet]. 2020 Jan 20 [cited 2025 Sep 16];5(0). Available from: https://jlpm.amegroups.org/article/view/5236

2. Dean L. The Rh blood group. In: Blood Groups and Red Cell Antigens [Internet] [Internet]. National Center for Biotechnology Information (US); 2005 [cited 2025 Sep 16]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2269/

3. CDC. Pregnancy and HIV, Viral Hepatitis, STDs, & Tuberculosis Prevention. 2025 [cited 2025 Sep 16]. Screening and testing for hiv, viral hepatitis, std & tuberculosis in pregnancy. Available from:https://www.cdc.gov/pregnancy-hiv-std-tb-hepatitis/php/screening/index.html

4. Bethune M, Alibrahim E, Davies B, Yong E. A pictorial guide for the second-trimester ultrasound. Australas J Ultrasound Med [Internet]. 2013 Aug [cited 2025 Sep 16];16(3):98–113. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029995/

5. Jabaz D, Jenkins SM. Sonography 2nd trimester assessment, protocols, and interpretation. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 [cited 2025 Sep 16]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK570574/

6. World Health Organization. Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy [cited 2025 Sep 25]. Available from: https://iris.who.int/bitstream/handle/10665/85975/WHO_NMH_MND_13.2_eng.pdf

Disclaimer:
The information provided on this website is for general educational and informational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.

Published September 30, 2025