Last Updated on February 14, 2023 by Dr. Shikha Shiromani
Pregnancy-related diabetes could pose serious risks to the mother and her baby. In addition, if left untreated, a woman with GDM (gestational diabetes mellitus) is more susceptible to infections, ketoacidosis, hypoglycemia, and pre-eclampsia. Therefore, it is crucial to get tested for gestational diabetes and prevent any complications at the earliest. This article discusses the correct time to undergo the tests to diagnose gestational diabetes, the reason the tests are done between 24-28 weeks, and why these tests are not done earlier in pregnancy.
When is a test performed for gestational diabetes?
The most sensitive test for diagnosing gestational diabetes and pre-diabetes is Oral Glucose Tolerance Test or OGTT. In order to screen for gestational diabetes, the OGTT is routinely performed at 24 to 28 weeks of pregnancy. However, if you have a history of gestational diabetes, one OGTT is done earlier in the pregnancy, and then another OGTT is done at 24 to 28 weeks of pregnancy if the first test is normal.
Other tests, such as fasting plasma glucose test and random plasma glucose test may also be used in some cases.
Why is a woman ideally tested between 24-28 weeks for gestational diabetes?
A gestational diabetes test is usually done between 24 and 28 weeks of pregnancy, as this is when gestational diabetes often develops. The test is done to screen for high blood sugar levels, which, if left untreated, can lead to complications for both the mother and the baby. The screening for GDM is usually done at 24-28 weeks of gestation because insulin resistance increases during the second trimester, and glucose levels rise in women who do not have the ability to produce enough insulin to adopt this resistance. At 28 weeks, the test provides enough time for early detection and intervention if necessary, which can help ensure a healthy pregnancy.
Why aren’t gestational diabetes tests done earlier in pregnancy?
Gestational diabetes tests are not typically done earlier in pregnancy because false results can be seen. Testing later in the second trimester, around 24-28 weeks, provides a clearer picture of the mother’s glucose levels and helps ensure an accurate diagnosis of gestational diabetes. Additionally, gestational diabetes often develops later in pregnancy, making it more likely to be detected in the latter part of the second trimester. However, some women are tested earlier than 24 weeks of gestation because they have risk factors for type 2 diabetes, such as obesity, family history of type 2 diabetes, or fetal macrosomia during a previous pregnancy.
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