A1c in pregnancy

Why A1c is lower in pregnancy

A1c measures glucose attached to hemoglobin over the life of red blood cells. In pregnancy those cells turn over faster, so A1c levels fall during normal pregnancy (ADA Standards 2026, sec. 15). The ADA also notes that A1c may not fully capture blood sugar after meals, which is what drives a large baby (macrosomia). For that reason A1c is used as a secondary measure in pregnancy, after glucose monitoring (ADA Standards 2026, sec. 15). Early in pregnancy, an A1c can also reflect glucose from the months before conception (NIDDK).

Early pregnancy: 5.9% and 6.5%

The ADA recommends testing people with risk factors before 15 weeks of pregnancy, and considering it for everyone, if they were not screened before conception (ADA Standards 2026, sec. 2). Two A1c lines matter here:

• 6.5% or higher. The criteria for undiagnosed diabetes in early pregnancy are the same as outside pregnancy. Someone found to have diabetes this early is classed as having diabetes complicating pregnancy, most often type 2 diabetes (ADA Standards 2026, sec. 2).
• 5.9% to 6.4%. The ADA calls this early abnormal glucose metabolism (or a fasting glucose of 110 to 125 mg/dL). It identifies people at higher risk of complications such as preeclampsia, a large baby and shoulder dystocia, and at high risk of a later gestational diabetes diagnosis (ADA Standards 2026, sec. 2).

Note that 5.9% is lower than the 6.5% used for diabetes and sits inside the usual prediabetes range of 5.7% to 6.4%.

Goals with diabetes in pregnancy

• Before conception: ideally an A1c below 6.5%, to lower the risk of birth defects, preeclampsia, a large baby and preterm birth (ADA Standards 2026, sec. 15).
• During pregnancy: ideally below 6% if this can be reached without significant hypoglycemia, relaxed to below 7% if needed to prevent it (ADA Standards 2026, sec. 15). In the second and third trimesters, an A1c below 6% has been linked with the lowest risk of a large baby, preterm delivery and preeclampsia (ADA Standards 2026, sec. 15).
• Glucose goals come first: fasting below 95 mg/dL, and either 1 hour after meals below 140 mg/dL or 2 hours after meals below 120 mg/dL (ADA Standards 2026, sec. 15).
• Testing more often: because of the changes in red blood cells, A1c may need checking more often than usual, for example monthly (ADA Standards 2026, sec. 15).

For goals outside pregnancy, see A1c goals in diabetes.

Gestational diabetes and after birth

The ADA recommends screening for gestational diabetes at 24 to 28 weeks in people not already found to have diabetes or early abnormal glucose metabolism (ADA Standards 2026, sec. 2). This is done with glucose tests (NIDDK). After a pregnancy with gestational diabetes:

• Test for prediabetes or diabetes at 4 to 12 weeks after birth, with a 75-g oral glucose tolerance test (ADA Standards 2026, sec. 2).
• Then keep screening every 1 to 3 years for life (ADA Standards 2026, sec. 2).

Frequently asked questions

Is a normal A1c different in pregnancy?

A1c runs slightly lower during pregnancy, in people with and without diabetes, because red blood cells turn over faster. Early in pregnancy the usual diagnostic cut points are used to look for diabetes that was already there.

What A1c is a concern in early pregnancy?

Before 15 weeks, an A1c of 6.5% or higher meets the standard criteria for diabetes. The ADA calls an A1c of 5.9% to 6.4% early abnormal glucose metabolism: a sign of higher risk of complications and of gestational diabetes later.

What is the A1c goal in pregnancy with diabetes?

Ideally below 6% if that can be reached without significant low blood sugar, relaxed to below 7% if needed to prevent it. Glucose monitoring comes first; A1c is a secondary measure in pregnancy.

Is gestational diabetes diagnosed with an A1c?

Screening for gestational diabetes is done at 24 to 28 weeks with glucose tests. After a pregnancy with gestational diabetes, the follow-up test at 4 to 12 weeks after birth is a 75-g oral glucose tolerance test.