What is the recommended follow‑up schedule for glucose monitoring in pregnant women with pre‑existing type 1 or type 2 diabetes or gestational diabetes during each trimester?

Glucose Monitoring Follow-Up Schedule in Pregnant Women with Diabetes

All pregnant women with pre-existing type 1, type 2, or gestational diabetes should perform daily self-monitoring of blood glucose 4–6 times per day (fasting and after each main meal) throughout pregnancy, with clinical follow-up visits every 1–2 weeks from diagnosis through delivery. 1, 2

Daily Self-Monitoring Requirements

Frequency and timing of blood glucose checks:

• Fasting glucose upon waking each morning 1, 3
• Postprandial glucose after breakfast, lunch, and dinner—choose either 1-hour OR 2-hour measurements consistently 1, 3
• Pre-meal glucose when using insulin pumps or basal-bolus therapy to adjust rapid-acting insulin doses 1
• Total of 4–6 blood glucose measurements daily to guide insulin titration 4, 3

Target glucose values throughout all trimesters:

• Fasting: < 95 mg/dL (5.3 mmol/L) 1, 3
• 1-hour postprandial: < 140 mg/dL (7.8 mmol/L) 1, 3
• 2-hour postprandial: < 120 mg/dL (6.7 mmol/L) 1, 3

Clinical Follow-Up Visit Schedule

Every 1–2 weeks from diagnosis through delivery for all women with any form of diabetes in pregnancy to optimize glucose control and monitor fetal growth. 2, 5

This intensive visit schedule applies equally across all three trimesters because:

• First trimester (weeks 0–13): Insulin sensitivity increases, insulin requirements drop by 12%, and hypoglycemia risk peaks—requiring close monitoring and frequent dose reductions 4, 6
• Second and third trimesters (weeks 14–36): Insulin resistance rises exponentially starting around week 16, with insulin needs increasing approximately 5% per week and often doubling or tripling by week 36—necessitating aggressive weekly or bi-weekly dose escalations 1, 4, 6
• Late third trimester (≥ week 36): Insulin requirements may plateau or decline; an abrupt unexplained drop signals possible placental insufficiency and demands immediate obstetric evaluation 4, 6

A1C Monitoring Frequency

Monthly A1C measurements throughout pregnancy due to increased red blood cell turnover that lowers A1C values compared to non-pregnant states. 1, 4

Target A1C:

• Optimal: < 6% (42 mmol/mol) if achievable without significant hypoglycemia 1, 6
• Acceptable alternative: < 7% (53 mmol/mol) when hypoglycemia risk is high 1, 6

Critical caveat: A1C serves as a secondary metric only—it may miss postprandial hyperglycemia that drives macrosomia, so daily blood glucose monitoring remains mandatory and cannot be replaced by A1C or continuous glucose monitoring metrics. 1, 4, 3

Continuous Glucose Monitoring (CGM)

When used in addition to (not as a substitute for) pre- and postprandial self-monitoring, real-time CGM in type 1 diabetes pregnancy reduces large-for-gestational-age births, neonatal hypoglycemia, and hospital length of stay without increasing maternal hypoglycemia. 1, 3

CGM metrics should not replace blood glucose monitoring for achieving optimal pre- and postprandial targets. 1

Fetal Surveillance Schedule

Ultrasound measurement of fetal abdominal circumference should begin in the second or early third trimester and be repeated every 2–4 weeks to guide management intensity. 3

• When fetal abdominal circumference is < 75th percentile (normal growth), less intensive management may be appropriate 3
• When fetal abdominal circumference is ≥ 75th percentile (excessive growth), lower glycemic targets or intensify pharmacologic therapy 3

Maternal perception of fetal movements should be monitored during the last 8–10 weeks of pregnancy, with immediate reporting of any reduction. 3

Postpartum Follow-Up for Gestational Diabetes

4–12 weeks postpartum: Perform a 75-g oral glucose tolerance test (OGTT) using non-pregnancy diagnostic criteria to detect persistent diabetes or prediabetes—do NOT use A1C at this visit because pregnancy-related changes and peripartum blood loss may falsely lower the value. 1, 3, 7

Long-term surveillance: Women with a history of gestational diabetes have a 50–70% risk of developing type 2 diabetes over 15–25 years, so perform diabetes screening every 1–3 years (or annually if additional risk factors are present) using fasting plasma glucose, A1C, or 75-g OGTT with non-pregnant thresholds. 1, 3, 8

Common Pitfalls to Avoid

• Never reduce monitoring frequency based on good control—insulin requirements change rapidly and unpredictably throughout pregnancy, especially after week 16 1, 4
• Do not rely on A1C alone to guide therapy—postprandial excursions drive fetal macrosomia and may be missed by A1C 4, 3
• Recognize that a sudden drop in insulin needs may indicate placental insufficiency rather than improved control and requires urgent obstetric evaluation 4, 6
• Provide comprehensive hypoglycemia education before initiating insulin, as pregnancy attenuates counter-regulatory hormone responses and increases first-trimester hypoglycemia risk 4, 6