1. Classification of Diabetes in Pregnancy
Understanding the distinctions between diabetes subtypes is foundational to appropriate intrapartum and postpartum management.
| Feature | A1GDM | A2GDM | Type 1 DM (Pregestational) | Type 2 DM (Pregestational) |
|---|---|---|---|---|
| Definition | GDM controlled by diet/exercise alone | GDM requiring pharmacotherapy | Autoimmune β-cell destruction; absolute insulin deficiency | Insulin resistance + relative β-cell failure |
| Onset | Diagnosed 24–28 weeks | Diagnosed 24–28 weeks | Pre-pregnancy | Pre-pregnancy |
| Treatment | Medical nutrition therapy + exercise | Insulin (preferred), metformin, or glyburide | Insulin (mandatory) | Insulin (preferred); transition from oral agents |
| Congenital anomaly risk | Not increased | Not increased | 6–12% (HbA1c-dependent) | 6–12% (HbA1c-dependent) |
| Preconception care | Not applicable | Not applicable | Critical (HbA1c <6.5% goal) | Critical (HbA1c <6.5% goal) |
| Aspirin prophylaxis | Not routine | Not routine | 81 mg/day starting 12–16 weeks | 81 mg/day starting 12–16 weeks |
| Delivery timing | 39 0/7–40 6/7 weeks | 39 0/7–39 6/7 weeks | 36–39 6/7 weeks (based on control/complications) | 36–39 6/7 weeks (based on control/complications) |
A1GDM vs. A2GDM: Both are diagnosed at 24–28 weeks via the two-step screening process (50-g glucose challenge followed by 100-g, 3-hour OGTT using Carpenter-Coustan criteria).[1] The distinction is made after diagnosis: patients whose glucose values remain at target with diet and exercise alone are classified as A1, while those requiring pharmacotherapy (~30% of GDM patients) are reclassified as A2.[1][2] A2GDM reflects more severe glucose intolerance and carries higher risks for preeclampsia, cesarean delivery, and large-for-gestational-age infants.[3]
Pregestational T1DM vs. T2DM: Both carry substantially elevated risks compared to GDM. A meta-analysis of 137 million pregnancies found pregestational diabetes associated with OR 4.46 for preeclampsia, OR 3.95 for LGA, OR 2.44 for congenital malformations, and OR 2.87 for stillbirth.[4] Despite T2DM often having lower HbA1c values, perinatal mortality may actually be higher in T2DM than T1DM (OR 1.50, 95% CI 1.15–1.96), likely reflecting later presentation, less preconception care, and more comorbidities including obesity and metabolic syndrome.[5] T1DM carries higher risks of maternal hypoglycemia (especially first trimester) and diabetic ketoacidosis, which can occur at lower glucose thresholds during pregnancy.[6][2]
The following figure illustrates the GDM screening pathway from early risk-factor-based screening through the standard two-step process at 24–28 weeks.
2. Intrapartum Blood Glucose Management
Target Glucose Range
ACOG Practice Bulletin No. 201 recommends an intrapartum glucose target of <110 mg/dL, with a goal of approximately 100 mg/dL.[1][7] The practical target range used in clinical settings is 70–110 mg/dL.[1] Glucose monitoring should be performed hourly during active labor using a bedside meter.[1][7]
It is worth noting that the evidence base for strict intrapartum targets is evolving. The PERMIT trial (2024, n=96) compared usual care (target 70–110 mg/dL) to permissive care (target 70–180 mg/dL) and found equivalent neonatal blood glucose between groups (57.9 vs. 57.1 mg/dL; adjusted mean difference −0.72, 95% CI −8.87 to 7.43), with 17% of the usual-care group requiring an insulin drip versus none in the permissive group.[8] Similarly, an RCT by Hamel et al. (n=76) in GDM found no difference in initial neonatal glucose between tight control (hourly checks, treat if >100 mg/dL) and liberalized control (every 4 hours, treat if >120 mg/dL).[9] Despite these findings, current ACOG guidelines still recommend the 70–110 mg/dL target.
ACOG Box 3 Protocol: Step-by-Step Intrapartum Insulin Management
This protocol, from ACOG Practice Bulletin No. 201, applies primarily to pregestational diabetes but is adapted for A2GDM as well:[7]
1. Night before delivery/induction: Give the usual dose of intermediate-acting (NPH) or long-acting (glargine) insulin at bedtime.
2. Morning of delivery: Withhold or reduce the morning insulin dose based on timing of admission and anticipated delivery.
3. IV access: Start normal saline upon admission.
4. Transition to dextrose: Once active labor begins OR glucose falls below 70 mg/dL, switch to D5 (5% dextrose) at 100–150 mL/h (2.5 mg/kg/min) to target glucose ~100 mg/dL.
5. Glucose monitoring: Check glucose hourly with bedside meter.
6. Insulin drip: If glucose exceeds 100 mg/dL, start regular insulin IV at 1.25 units/h and titrate based on hourly readings.
Key Differences by Diabetes Subtype During Labor
| Diabetes Type | Insulin Requirement in Labor | Key Considerations |
|---|---|---|
| A1GDM | Usually none | Monitor glucose; IV dextrose if <70 mg/dL; insulin drip rarely needed[1] |
| A2GDM | May need insulin drip | Withhold/reduce morning insulin; start drip if glucose >100–110 mg/dL[1], [2] |
| T1DM | Always required | Never completely stop insulin; if hypoglycemic, give IV dextrose and reduce (not stop) insulin rate[1] |
| T2DM | May or may not be needed | Endogenous insulin production may suffice during labor; monitor and treat as needed[1] |
Insulin Pump Management During Labor
Patients using an insulin pump (CSII) may continue their basal infusion during labor as an alternative to transitioning to an IV insulin drip.[1] An RCT of 70 participants comparing CSII continuation to IV insulin infusion during labor found no difference in neonatal hypoglycemia or secondary outcomes.[10] For patients on automated insulin delivery (AID) systems, device-specific intrapartum settings have been proposed by an international consensus statement (2026): for example, Tandem Control-IQ should use the sleep activity range of 112–120 mg/dL, and MiniMed 780G can remain at a 99 mg/dL target with active insulin time of 2 hours.[11]
3. Medication Management at Admission for Induction or Active Labor
Medications to DISCONTINUE
| Medication | When to Stop | Rationale | Reference |
|---|---|---|---|
| Glyburide (sulfonylurea) | ≥2 weeks before expected delivery | FDA label: risk of prolonged neonatal hypoglycemia lasting 4–10 days; crosses placenta (cord levels ~50–70% of maternal) | [1], [2] |
| Metformin | On admission for labor/delivery | Hold when NPO/in active labor; transition to IV insulin if needed; no specific pre-delivery timeline mandated | [3], [4] |
| Scheduled subcutaneous rapid-acting insulin (lispro, aspart) | On admission | Replace with IV regular insulin drip per Box 3 protocol if glucose >100 mg/dL | [5] |
| Morning dose of NPH or long-acting insulin | Withhold or reduce on morning of delivery | Bedtime dose the night before should be given at usual dose | [5] |
| GLP-1 receptor agonists | Should already be discontinued (≥2 months before conception for semaglutide) | Not approved in pregnancy; teratogenic concerns | [3], [6] |
| SGLT-2 inhibitors | Should already be discontinued preconception | Not studied in pregnancy | [6] |
| ACE inhibitors / ARBs | Should already be discontinued (1st trimester) | Teratogenic (renal agenesis, oligohydramnios) | [3], [7] |
| Statins | Should already be discontinued preconception | Teratogenicity concerns | [3], [7] |
Medications to CONTINUE or INITIATE
| Medication | Action | Details | Reference |
|---|---|---|---|
| Bedtime NPH or long-acting insulin | Continue the night before induction | Provides basal coverage through labor | [1] |
| Insulin pump (CSII) basal rate | May continue during labor | Equivalent outcomes to IV insulin in RCT data; varies by institution | [2], [3] |
| IV regular insulin drip | Initiate if glucose >100 mg/dL | 1.25 units/h, titrate hourly | [1] |
| IV D5 (5% dextrose) | Initiate when active labor begins or glucose <70 mg/dL | 100–150 mL/h (2.5 mg/kg/min) | [1] |
| IV normal saline | Start on admission | Initial fluid; transition to D5 as above | [1] |
Special note on insulin degludec (ultra-long-acting, ≥42h duration): Its prolonged duration presents unique challenges at delivery. The morning dose should be withheld or reduced, but clinicians must be aware that its effects persist far longer than glargine, increasing the risk of postpartum hypoglycemia.[10]
4. Postpartum Recommendations by Diabetes Subtype
Immediate Postpartum Insulin Adjustment
Insulin sensitivity increases dramatically after delivery of the placenta due to loss of placental counter-regulatory hormones. Immediate postpartum insulin requirements are approximately 34% lower than prepregnancy levels.[10]
| Diabetes Type | Postpartum Medication Management | Reference |
|---|---|---|
| A1GDM | Discontinue all glucose monitoring and dietary restrictions; no medications needed | [1], [2] |
| A2GDM | Discontinue insulin and/or oral agents; monitor for persistent hyperglycemia; postpartum OGTT at 4–12 weeks | [1], [2] |
| T1DM | Reduce basal insulin to ⅓–½ of predelivery dose; reduce bolus insulin to ⅓–½ of predelivery dose once eating; pump users reduce basal by ~50% | [3], [4] |
| T2DM | Same insulin reductions as T1DM; may resume metformin (safe in breastfeeding); resume ACE inhibitors/ARBs if needed | [3], [5] |
Postpartum Glucose Testing for GDM
| Test | Timing | Method | Notes | Reference |
|---|---|---|---|---|
| Initial screening | 4–12 weeks postpartum | 75-g, 2-hour OGTT (preferred) | Uses nonpregnancy diagnostic criteria; HbA1c is less sensitive at this time point due to peripartum blood loss and RBC turnover | [1], [2], [3] |
| Alternative: inpatient screening | Postpartum day 2 | 75-g OGTT | ACOG 2024 update; high negative predictive value (≥97.5%); nearly 100% adherence vs. ~50% for outpatient testing | [1] |
| Ongoing screening (if initial test normal) | Every 1–3 years, lifelong | Annual HbA1c, annual FPG, or triennial OGTT | Lifetime risk of T2DM after GDM is ~50–60%; 10-fold increased risk vs. no GDM | [2], [3] |
| If prediabetes found | Ongoing | Metformin and/or intensive lifestyle intervention | NNT of 8 for metformin and 12 for lifestyle over 10 years to prevent T2DM | [4], [5] |
The following figure illustrates the postpartum screening algorithm for GDM, including OGTT and HbA1c pathways with specific glucose thresholds.
Figure 3 Postpartum follow-up for gestational diabetes mellitus. Information from references 2, 4, 25, and 71.
Breastfeeding Considerations
Breastfeeding is universally recommended for all diabetes subtypes (ADA Grade A).[13] For women with a history of GDM, breastfeeding is associated with reduced risk of developing type 2 diabetes later in life (OR 0.68, 95% CI 0.57–0.82).[13][3]
For women with pregestational diabetes, several specific considerations apply:
- Hypoglycemia risk during breastfeeding is a major concern, as carbohydrates are transferred into breast milk. Insulin doses may need further reduction, and a snack with each feeding session may be helpful.[1][18]
- An additional 500 kcal/day above prepregnancy caloric intake is recommended for nonobese breastfeeding women, with a minimum of 210 g carbohydrates daily for T1DM to prevent hypoglycemia and ketoacidosis.[1][19]
- However, a prospective study of 26 breastfeeding mothers with T1DM found that night-time hypoglycemia after breastfeeding was rare (CGM <4.0 mmol/L within 3 hours occurred after only 4.6% of 438 recorded night-time breastfeeds without carbohydrate intake), suggesting routine carbohydrate intake at every night-time feed may be unnecessary when insulin doses are properly adjusted.[13]
Medication safety during breastfeeding:
| Medication | Breastfeeding Safety | Reference |
|---|---|---|
| Insulin (all types) | Safe — does not pass into breast milk | [1] |
| Metformin | Safe — minimal transfer to breast milk | [1] |
| Glyburide/glipizide | Acceptable — not found in significant amounts in breast milk | [1] |
| ACE inhibitors | Generally acceptable — minimal breast milk transfer | [1] |
| GLP-1 receptor agonists | Not recommended — no lactation data | [1] |
| SGLT-2 inhibitors | Not recommended — no lactation data | [1] |
| Statins | Avoid — limited data; teratogenic concerns if future pregnancy | [2] |
Contraception Counseling
The ADA recommends that a contraceptive plan be discussed and implemented with all people with diabetes of childbearing potential (Grade A).[13][21] Long-acting reversible contraception (LARC) — IUDs and implantable progestins — is recommended as first-line for all diabetes subtypes because it is the most effective form of contraception and does not affect glycemic control.[1][18][21] Fertility may return as soon as 6 weeks postpartum in women who are not exclusively breastfeeding, making the immediate postpartum period an important window for LARC initiation.[18] The WHO recommends an interpregnancy interval of at least 24 months.[22]
For women with pregestational diabetes and serious vasculopathy, sterilization should be discussed.[1] For those with vascular complications, progestin-only methods are preferred over combined hormonal contraceptives.[22]
Long-Term Cardiovascular Risk
Women with prior GDM have a 2-fold higher risk for cardiovascular disease and are more likely to develop hypertension, dyslipidemia, obesity, and fatty liver.[22] The 2026 AHA/ACC/ADA/ASN CKM guideline recommends that individuals with prior GDM undergo longitudinal assessments for glycemia, lipids, and kidney function at least every 2–3 years, consistent with CKM syndrome stage 1 management.[20] For pregestational diabetes, annual assessments for dyslipidemia, vasculopathy, retinopathy, nephropathy, and cardiac dysfunction should continue.[20] Notably, pregestational diabetes increases the risk of de novo postpartum hypertension (13% vs. 3%) and persistent postpartum hypertension (21.5% vs. 5.6%).[21]
Summary - TLDR
The key principle across all subtypes is that intrapartum glucose management aims for 70–110 mg/dL with hourly monitoring, using the ACOG Box 3 protocol of IV normal saline → D5 when active labor begins or glucose <70 → IV regular insulin at 1.25 units/h if glucose >100 mg/dL.[7] The intensity of management scales with disease severity: A1GDM rarely needs intervention beyond monitoring, A2GDM may need an insulin drip, T2DM may or may not require insulin during labor, and T1DM always requires insulin — it should never be completely discontinued.[1] Glyburide must be stopped ≥2 weeks before delivery, metformin is held on admission, and all scheduled subcutaneous insulin is replaced by IV insulin or continued via pump.[10][13][7] Postpartum, GDM medications are discontinued with OGTT screening at 4–12 weeks and lifelong follow-up, while pregestational diabetes requires immediate insulin dose reduction to ⅓–½ of predelivery doses with ongoing comprehensive diabetes management.[1][10][13]
References
- •ACOG Practice Bulletin No. 201: Pregestational Diabetes Mellitus. American College of Obstetricians and Gynecologists' Committee on Practice Bulletins—Obstetrics. Obstetrics and Gynecology. 2018;132(6):e228-e248. doi:10.1097/AOG.0000000000002960.
- •Application of Continuous Glucose Monitoring and Automated Insulin Delivery Technologies for Pregnant Women With Type 1, Type 2, or Gestational Diabetes: An International Consensus Statement. Benhalima K, Durnwald C, Sweeting A, et al. The Lancet. Diabetes & Endocrinology. 2026;14(2):157-177. doi:10.1016/S2213-8587(25)00335-3.
- •Gestational Diabetes Mellitus: Update on Screening, Diagnosis, and Management. Will JS, Crellin H. American Family Physician. 2023;108(3):249-258.
- •Permissive Intrapartum Glucose Control: An Equivalence Randomized Control Trial (PERMIT). Bitar G, Bravo R, Pedroza C, et al. American Journal of Obstetrics and Gynecology. 2024;231(3):355.e1-355.e11. doi:10.1016/j.ajog.2024.05.053.
- •Intrapartum Glucose Management in Women With Gestational Diabetes Mellitus: A Randomized Controlled Trial. Hamel MS, Kanno LM, Has P, et al. Obstetrics and Gynecology. 2019;133(6):1171-1177. doi:10.1097/AOG.0000000000003257.
- •Management of Type 1 Diabetes in Pregnancy: Update on Lifestyle, Pharmacological Treatment, and Novel Technologies for Achieving Glycaemic Targets. Benhalima K, Beunen K, Siegelaar SE, et al. The Lancet. Diabetes & Endocrinology. 2023;11(7):490-508. doi:10.1016/S2213-8587(23)00116-X.
- •Different Intensities of Glycaemic Control for Pregnant Women With Pre-Existing Diabetes. Middleton P, Crowther CA, Simmonds L. The Cochrane Database of Systematic Reviews. 2016;(5):CD008540. doi:10.1002/14651858.CD008540.pub4.
- •Evaluation of an Intrapartum Insulin Regimen for Women With Diabetes. Dude AM, Niznik C, Peaceman AM, Yee LM. Obstetrics and Gynecology. 2020;136(2):411-416. doi:10.1097/AOG.0000000000003940.
- •Intrapartum Care for People With Diabetes-Working Towards Evidence-Based Management. Fishel Bartal M. American Journal of Perinatology. 2025;42(9):1103-1108. doi:10.1055/a-2405-1846.
- •Glyburide. Food and Drug Administration. Updated date: 2023-01-09.
- •Glyburide. Food and Drug Administration. Updated date: 2021-07-01.
- •glyburide-metformin hydrochloride. Food and Drug Administration. Updated date: 2026-06-09.
- •15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes-2026. American Diabetes Association Professional Practice Committee for Diabetes*. Diabetes Care. 2026;49(Supplement_1):S321-S338. doi:10.2337/dc26-S015.
- •Epidemiology and Management of Gestational Diabetes. Sweeting A, Hannah W, Backman H, et al. Lancet (London, England). 2024;404(10448):175-192. doi:10.1016/S0140-6736(24)00825-0.
- •SMFM Statement: Pharmacological Treatment of Gestational Diabetes. Society of Maternal-Fetal Medicine (SMFM) Publications Committee. Electronic address: pubs@smfm.org. American Journal of Obstetrics and Gynecology. 2018;218(5):B2-B4. doi:10.1016/j.ajog.2018.01.041.
- •A Practical Approach to Insulin Pump, Continuous Glucose Monitoring, and Automated Insulin Delivery in the Management of Type 1 Diabetes in Pregnancy. Wong M, Maayeh MG, Saade GR, Saad A. American Journal of Perinatology. 2026;43(8):1072-1081. doi:10.1055/a-2854-5752.
- •Group vs Individual Prenatal Care and Gestational Diabetes Outcomes: A Secondary Analysis of a Randomized Clinical Trial. Chen Y, Crockett AH, Britt JL, et al. JAMA Network Open. 2023;6(8):e2330763. doi:10.1001/jamanetworkopen.2023.30763.
- •Management of Preexisting Diabetes in Pregnancy: A Review. Alexopoulos AS, Blair R, Peters AL. JAMA. 2019;321(18):1811-1819. doi:10.1001/jama.2019.4981.
- •Society for Maternal-Fetal Medicine Special Statement: Updated Checklist for Antepartum Care of Pregestational Diabetes Mellitus. Hameed AB, Combs CA. American Journal of Obstetrics and Gynecology. 2020;223(5):B2-B5. doi:10.1016/j.ajog.2020.08.063.
- •ACOG Clinical Practice Update: Screening for Gestational and Pregestational Diabetes in Pregnancy and Postpartum. Obstetrics and Gynecology. 2024;144(1):e20-e23. doi:10.1097/AOG.0000000000005612.
- •2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2026. American Diabetes Association Professional Practice Committee for Diabetes*. Diabetes Care. 2026;49(Supplement_1):S27-S49. doi:10.2337/dc26-S002.
- •Guidelines and Recommendations for Laboratory Analysis in the Diagnosis and Management of Diabetes Mellitus. Sacks DB, Arnold M, Bakris GL, et al. Diabetes Care. 2023;46(10):e151-e199. doi:10.2337/dci23-0036.