Preconception, Pregnancy, Postpartum & Gestational Diabetes
Key Takeaways
- Preconception A1C goal is <6.5%, since major fetal organogenesis occurs at 5-8 weeks of gestation, before pregnancy is often recognized.
- ADA pregnancy glycemic targets are fasting <95 mg/dL, 1-hour postprandial <140 mg/dL, 2-hour postprandial <120 mg/dL, and A1C <6%.
- Insulin is the preferred glucose-lowering agent in pregnancy; ACE inhibitors, ARBs, and statins must be stopped before or upon confirming pregnancy.
- Insulin requirements drop by 50% or more immediately after delivery, creating a high risk of postpartum hypoglycemia.
- GDM is screened at 24-28 weeks gestation, and a 75 g, 2-hour OGTT is used to screen for persistent diabetes at 4-12 weeks postpartum.
Preconception Care
Preconception planning is one of the highest-leverage interventions in diabetes care because major fetal organogenesis occurs at 5-8 weeks of gestation — often before a person knows they are pregnant. People with preexisting type 1 or type 2 diabetes who are planning pregnancy should work toward an A1C goal of <6.5% before conception, using only therapies approved for use in pregnancy; achieving this target before conception is associated with the lowest risk of congenital anomalies, preeclampsia, and preterm birth. ADA guidance also specifies preconception glucose goals to guide therapy adjustments in addition to the A1C target — the same numeric targets used during pregnancy itself (see table below). Counseling must explicitly address avoiding excessive hypoglycemia while working toward these tighter goals, since aggressive tightening without support can itself become unsafe.
Preconception care also includes:
- Folic acid 400-800 mcg/day, started before conception to reduce neural tube defect risk
- Contraception counseling for anyone not actively trying to conceive, continued until glycemic goals are met and pregnancy is planned
- Discontinuing potentially teratogenic medications before conception (detailed below)
- Reviewing existing complications before conception — a dilated eye exam is recommended before or early in pregnancy because retinopathy can progress rapidly with pregnancy's metabolic and hormonal changes, and kidney function should be assessed since nephropathy also affects pregnancy risk and management
Preconception counseling is ideally initiated well before a planned pregnancy so that glycemic goals, medication changes, and complication screening are complete rather than rushed once pregnancy is confirmed.
Pregnancy Glycemic Targets
The following ADA-recommended targets apply to all pregnant people with diabetes (preexisting or gestational) and must be taught precisely — these are frequently tested numbers:
| Measure | Target |
|---|---|
| Fasting plasma glucose | <95 mg/dL |
| 1-hour postprandial glucose | <140 mg/dL |
| 2-hour postprandial glucose | <120 mg/dL |
| A1C | <6% (a less stringent goal of <7% may be appropriate if needed to prevent hypoglycemia) |
| CGM time in range (63-140 mg/dL) | >70% |
| CGM time below range (<63 mg/dL) | <4% (<1% below 54 mg/dL) |
| CGM time above range (>140 mg/dL) | <25% |
A1C targets are lower in pregnancy than in the general adult population because increased red blood cell turnover shortens the interval A1C reflects.
Medication Safety in Pregnancy
Insulin is the preferred agent for glycemic control throughout pregnancy in type 1 diabetes, type 2 diabetes, and gestational diabetes requiring pharmacotherapy — it does not cross the placenta in clinically significant amounts and is the most titratable option. Oral agents carry documented tradeoffs: both metformin and glyburide cross the placenta, and glyburide is associated with higher rates of neonatal hypoglycemia and macrosomia compared with insulin, so it is not recommended as first-line therapy. Metformin is sometimes continued or initiated in select circumstances (for example, ongoing use for PCOS or type 2 diabetes, or shared decision-making around cost and access in gestational diabetes), but insulin remains the preferred agent overall, especially in type 1 diabetes.
Several medication classes must be stopped before or immediately upon confirming pregnancy because of teratogenic or fetal risk:
- ACE inhibitors and ARBs — associated with fetal renal dysgenesis and other anomalies
- Statins — discontinued in pregnancy
- Most non-insulin glucose-lowering agents — GLP-1 receptor agonists, SGLT2 inhibitors, DPP-4 inhibitors, and (with the exceptions above) sulfonylureas and TZDs are switched to insulin
Low-dose aspirin for preeclampsia prophylaxis is typically continued or initiated in people with type 1 or type 2 diabetes, and thyroid replacement doses are monitored closely, since levothyroxine requirements often increase in pregnancy.
Postpartum Care
Insulin requirements drop sharply immediately after delivery — often by 50% or more from late-pregnancy doses — because the placenta was the source of the insulin-resistance-driving hormones. This creates a high-risk window for postpartum hypoglycemia, particularly in the first 24-48 hours and with breastfeeding, so doses must be reassessed rather than continued at prenatal levels. Breastfeeding is encouraged for its metabolic benefits to the parent and the infant, with attention to a pre-feeding snack to reduce hypoglycemia risk. Contraception counseling should occur before discharge, and postpartum depression screening is important given the elevated risk in people with diabetes.
Gestational Diabetes Mellitus (GDM)
Universal screening for GDM occurs at 24-28 weeks of gestation (earlier first-trimester testing is used only for those with risk factors, applying standard non-pregnant criteria to catch preexisting undiagnosed diabetes). Two screening approaches are used:
| Approach | Test | Diagnostic Threshold |
|---|---|---|
| One-step | 75 g OGTT | GDM if any one value is met/exceeded: fasting ≥92 mg/dL, 1-hour ≥180 mg/dL, 2-hour ≥153 mg/dL |
| Two-step | 50 g glucose challenge screen, then 100 g OGTT if positive (Carpenter-Coustan criteria) | GDM if two or more values are met/exceeded: fasting ≥95, 1-hour ≥180, 2-hour ≥155, 3-hour ≥140 mg/dL |
Medical nutrition therapy and physical activity are first-line management; insulin is added when glucose targets are not met with lifestyle measures alone, and insulin remains ADA's preferred pharmacologic agent when medication is needed. Because GDM signals substantially elevated future type 2 diabetes risk, ADA recommends postpartum screening with a 75 g, 2-hour OGTT at 4-12 weeks postpartum (more sensitive in the early postpartum period than fasting glucose or A1C alone), followed by ongoing screening at least every 1-3 years thereafter.
What A1C goal does ADA recommend a person with preexisting diabetes achieve prior to conception?
A pregnant patient with type 1 diabetes checks her blood glucose 1 hour after breakfast. Which value meets the ADA pregnancy glycemic target?
Which glucose-lowering agent does ADA identify as the preferred choice for managing hyperglycemia during pregnancy?