A pregnant woman’s fasting blood sugar should stay between 70 and 95 mg/dL, with readings under 140 mg/dL one hour after meals and under 120 mg/dL two hours after meals. These targets are tighter than what’s recommended outside of pregnancy because even moderately elevated blood sugar carries real risks for the baby.
Target Numbers During Pregnancy
The specific targets depend on whether you had diabetes before pregnancy or developed gestational diabetes during it, but the ranges overlap considerably. For gestational diabetes, the American Diabetes Association recommends a fasting blood sugar of 95 mg/dL or lower, a one-hour post-meal reading of 140 mg/dL or lower, and a two-hour post-meal reading of 120 mg/dL or lower.
For women who entered pregnancy with type 1 or type 2 diabetes, the goals are slightly tighter: fasting and pre-meal readings of 60 to 99 mg/dL, and peak post-meal readings of 100 to 129 mg/dL. These stricter targets reflect the fact that consistently elevated glucose earlier in pregnancy can affect fetal development during critical windows.
If hitting those numbers causes frequent low blood sugar episodes, your provider may loosen the targets slightly. The American College of Obstetricians and Gynecologists allows a fasting target under 90 mg/dL and one-hour post-meal readings under 130 to 140 mg/dL. The ADA’s relaxed thresholds go up to 105 mg/dL fasting and 155 mg/dL one hour after eating. The point is to find a range that protects the baby without putting you at risk for dangerous drops.
Why Pregnancy Changes Blood Sugar
Your body’s relationship with blood sugar shifts dramatically during pregnancy. By late pregnancy, your body produces about 30% more glucose than usual to fuel the baby’s growth. At the same time, your tissues become roughly 50% less sensitive to insulin. This combination means glucose lingers in your bloodstream longer after meals, which is why post-meal numbers matter so much during pregnancy.
This insulin resistance is a normal adaptation. Your body is prioritizing glucose delivery to the placenta. But when the system can’t compensate well enough, blood sugar rises above those target thresholds, and that’s when gestational diabetes develops.
What Happens When Blood Sugar Stays Too High
The main concern with elevated blood sugar during pregnancy is that extra glucose crosses the placenta and reaches the baby, who then produces more insulin to process it. That excess insulin acts like a growth hormone, causing the baby to grow larger than normal, a condition called macrosomia. Research shows the risk of macrosomia doesn’t climb significantly until average glucose levels reach about 130 mg/dL, at which point 65% of mothers in one study delivered a large baby, compared with 27% of those with lower values.
A larger baby increases the likelihood of birth injuries, emergency cesarean delivery, and shoulder complications during vaginal birth. After delivery, the baby’s insulin-producing system is still running high, which can cause a steep drop in the newborn’s blood sugar in the first hours of life. Persistently high blood sugar also raises the risk of preeclampsia and preterm delivery. Women with A1c values between 5.7% and 6.4% during pregnancy face higher rates of both.
How A1c Fits Into the Picture
A1c measures your average blood sugar over the past two to three months. During pregnancy, the ADA recommends keeping A1c below 6%. But interpreting A1c in pregnancy is tricky because your body is producing red blood cells faster than usual, especially in the first half of pregnancy. Since A1c reflects glucose attached to red blood cells, a surge of new cells can make the number look artificially low early on.
Later in pregnancy, hemoglobin levels naturally drop (a mild anemia that’s common and expected), and this can push A1c readings up by 0.1 to 0.2% independent of any actual change in blood sugar. Iron deficiency amplifies this effect. For these reasons, daily glucose monitoring gives a more reliable and actionable picture than A1c alone during pregnancy.
How Gestational Diabetes Is Diagnosed
Most providers screen for gestational diabetes between 24 and 28 weeks using one of two approaches. The more common two-step process starts with a one-hour glucose challenge: you drink a sugary solution, and your blood is drawn an hour later. A result of 190 mg/dL or higher indicates gestational diabetes outright. If your result is elevated but below 190, you move on to a three-hour test.
For the three-hour test, you fast overnight, then drink a higher-concentration glucose solution. Blood is drawn at fasting, one hour, two hours, and three hours. You’re diagnosed with gestational diabetes if two or more values exceed the cutoffs: fasting above 95, one-hour above 180, two-hour above 155, or three-hour above 140 mg/dL.
Some providers use a single-step, two-hour test instead. With this approach, any one abnormal value is enough for a diagnosis: fasting at or above 92 mg/dL, one-hour at or above 180, or two-hour at or above 153. The single-step test catches more cases because its thresholds are lower and only one abnormal value is needed.
How and When to Check Your Blood Sugar
If you’re diagnosed with gestational diabetes or managing preexisting diabetes, expect to check your blood sugar at least four times a day: once in the morning before eating (your fasting number) and once after each meal. Post-meal readings are typically taken either one hour or two hours after your first bite, depending on which target your provider wants you to use.
Fasting numbers reflect how well your body manages glucose overnight without food. Post-meal numbers show how your body handles the carbohydrates you actually eat, which makes them especially useful for adjusting your diet. If your one-hour post-meal readings consistently land above 140, that’s a signal to look at the size or composition of your meals, particularly the carbohydrate portion.
Many women find that fasting numbers are the hardest to control because they’re driven by hormones rather than food choices. Your liver releases glucose overnight in response to pregnancy hormones, and there’s only so much dietary adjustment can do about that. When fasting numbers stay stubbornly above target despite consistent eating habits, medication or insulin often becomes part of the plan.
What Normal Looks Like Without Diabetes
If you don’t have gestational diabetes or preexisting diabetes, you generally won’t be asked to monitor your blood sugar at home. In a healthy pregnancy, the body compensates for increasing insulin resistance by producing more insulin, and blood sugar stays within normal ranges without intervention. Fasting levels in healthy pregnant women typically run between 70 and 89 mg/dL, and post-meal spikes rarely exceed 120 mg/dL.
Even without a diabetes diagnosis, blood sugar isn’t irrelevant. The hormonal shifts of pregnancy put every woman somewhere on the insulin resistance spectrum. Eating balanced meals with protein, fat, and fiber alongside carbohydrates helps blunt post-meal glucose spikes, and staying physically active improves insulin sensitivity. These habits benefit blood sugar regulation whether or not you’re formally tracking numbers.