Can You Rest Assured After the Glucose Challenge Test is Normal? Do Not Underestimate the Tolerance of Hyperglycemia

Speaking of the most difficult "checkpoint" for pregnant women to check during pregnancy, blood sugar must be on the list. Is diabetes diagnosed during pregnancy different from the diabetes we often say? Normal of the glucose challenge test means that you are really pass?

Speaking of the most difficult "checkpoint" for pregnant women to check during pregnancy, blood sugar must be on the list. Is diabetes diagnosed during pregnancy different from the diabetes we often say? Normal of the glucose challenge test means that you are really pass?

What is the Screening of the Glucose Challenge Test in Pregnancy?

Diabetes is divided into four types: type 1 diabetes, type 2 diabetes, special types diabetes and gestational diabetes. Pregnancy glucose challenge test is the last one - gestational diabetes.

"Gestational diabetes " and " pregnancy complicated by diabetes" are easily distinguished from the definition of disease. Gestational diabetes is defined as: the first discovered or first-onset diabetes after pregnancy.  This definition includes two cases, one is that the patient has diabetes before pregnancy but is not diagnosed; the other is that the patient has not had diabetes before and has diabetes after pregnancy.  Pregnancy complicated by diabetes is that "diabetes have been detected before pregnancy, but can be pregnant after evaluation."

For Them, the Glucose Challenge Test Comes Earlier

The time of glucose challenge test is generally recommended in 24-28 weeks of pregnancy, and there is no significant difference in the abnormal detection rate of diabetes screening after 24 weeks of gestation [2]. But for some pregnant mothers, it is safer to have earlier glucose challenge test.

The first type is pregnant mothers who have more drinking, eating, urination yet weight loss; the second type is pregnant mothers who have no "three more and one less" but have high-risk factors of diabetes (family history of diabetes , history of macrosomia delivery, fetal overgrowth, etc.).

At the same time, as the age increases, the metabolic capacity of the body decreases, and the value of glucose challenge test also increases.  Therefore, for older women, the test should be done in a timely manner.

The Right "Way" for Glucose Challenge Test

The first step of "glucose challenge test" is glucose abnormality screening (GCT): dissolve 50g glucose powder in 200ml of water, drink it up in 5 minutes, count the time from the first sip, and take blood sample for detection one hour later, take the blood glucose value ≥ 7.8mmol as the standard of glucose abnormality.

The second step is to carry out the glucose tolerance test (OGTT): pregnant women with abnormal glucose need fasting at least 8 hours, dissolve 75g of glucose powder in 300ml of water, drink it up within 5 minutes, and take blood samples for blood glucose check after 1h, 2h and 3h respectively. If 5.1 mmol/L ≤ fasting blood sugar < 7.0 mmol/L, OGTT 1 h blood glucose ≥ 10.0 mmol / L, 8.5 mmol / L ≤ OGTT2 h blood glucose <11.1mmol / L, gestational diabetes(GDM)[1] can be diagnosed in line with any of the above criteria.

The pregnant mother to be tested can refer to the following instructions for preparation:

1. Eat regularly 2-3 days before the test, and do not eat too sweet food.

2. Fasting 12 hours before test, but drinking water is acceptable.

3. After getting the prepared sugar water, the doctor generally requires to drink it within 1 minute, and the slowest time is no more than 5 minutes.  It has been confirmed that glucose consumption in 3-5 minutes is beneficial to reduce the occurrence of OGTT adverse reactions [3].

4. The first blood glucose test can only be carried out after taking sugar water for more than 1 hour (timing starts from the first sip), during which time, you can walk properly, but not too long or exercise too much.

5. 30% pregnant mothers will have nausea, dizziness, palpitation, acid reflux and other adverse reactions after  glucose challenge test, and which is a normal phenomenon. It is suggested that pregnant mother should use 40 ℃ warm boiled water to brew the glucose powder, and drink it slowly within 3-5 minutes instead of "one mouthful".

Don’t Hurry to Celebrate,
It’s Not Over Yet About The Blood Glucose After Glucose Challenge Test Is Normal

Research shows that [2], the rate of missed diagnosis of glucose challenge test is still about 10%, which is common in pregnant women with normal GCT and OGTT in the early or middle stage of pregnancy, but with high blood glucose in the late stage of pregnancy.  If there are abnormalities such as excessive weight growth, excessive amniotic fluid and fetal growth in late pregnancy, the possibility of blood glucose rise should be considered.  At the same time, for pregnant mothers with high-risk factors who have glucose challenge test in advance, blood glucose reexamination should be carried out in the later stage of pregnancy to ensure the safety of mother and child.

Finally, let’s distinguish between the"glucose challenge test" and "down’s screening", the "down’s screening" is a screening conducted at 16-18 weeks of gestation to determine the risk factors of fetal mongolian idiocy and neural tube defects. It is completely different except for the pronunciation, so don’t confuse it.


[1] Guidelines for the Prevention and Treatment of Type 2 Diabetes in China (2017 edition) [J]. Chinese Journal of Practical Internal Medicine, 2018, 38 (04): 292-344

[2] Zhao Songzhi. Analysis of Factors Affecting the Screening Results of Gestational Diabetes [J]. Maternal and Child Health Care of China (25)

[3] Yang Huizhen [1], Wang Xiaomin [1], Meng Zuolong [1], et al. Analysis of Influencing Factors of Adverse Reactions in Oral Glucose Tolerance Test in Healthy Population[J]. Journal of Nursing, 2010(10)