Preconception diabetes care substantially reduces risks of congenital anomalies, miscarriage, and other adverse pregnancy outcomes — the first 6 to 10 weeks of fetal development are most sensitive to maternal glucose levels, and most major organs form before many women know they are pregnant. A1C below 6.5 percent before conception (some specialists target below 6.0 percent), folate 400 to 1000 mcg daily, medication review with switching of most non-insulin diabetes medications, complication screening, and contraception until ready are the foundation. Starting 3 to 6 months before trying to conceive gives time to reach targets safely.
Why Preconception Care Matters
The earliest weeks of pregnancy — when most major fetal organs form — usually happen before a woman knows she is pregnant. By the time pregnancy is confirmed (typically 4 to 6 weeks), critical windows of development have already passed. Maternal glucose during this window correlates strongly with several adverse outcomes:
- Congenital anomalies — heart defects, neural tube defects, others
- Miscarriage — risk doubles or more with high A1C
- Preterm delivery
- Preeclampsia later in pregnancy
- Macrosomia and birth complications
- Neonatal complications
Preconception care can substantially reduce these risks. Studies show that organized preconception programs reduce congenital anomaly rates from 6 to 9 percent (in unplanned high-A1C pregnancies) to 1 to 2 percent (close to the general population baseline).
The A1C Target
- ADA recommendation: Below 6.5 percent before conception, if achievable without significant hypoglycemia
- Some specialists target: Below 6.0 percent for women who can reach it without frequent lows
- The relationship is continuous: Every 1 percent reduction in pre-pregnancy A1C corresponds to lower anomaly risk
- Use reliable contraception until target is reached
- CGM data (time in range, time below 63 mg/dL) increasingly supplements A1C
For more on what A1C means, see our resource on A1C levels.
Folate and Other Supplements
| Supplement | Dose / Detail |
|---|---|
| Folate | 400–1000 mcg daily; higher (4 mg) if prior NTD pregnancy |
| Iron | Per prenatal vitamin; supplement more if deficient |
| Calcium | 1000 mg/day from diet or supplement |
| Vitamin D | Repletion if deficient; many prenatals include 400–800 IU |
| Iodine | 150 mcg/day in prenatal vitamin |
| DHA | 200–300 mg/day; from prenatal or fish oil |
| B12 | Check if on long-term metformin |
Medication Review
Medications to Stop or Switch
- ACE inhibitors (lisinopril, enalapril): Fetal renal damage, oligohydramnios. Switch to labetalol, nifedipine, or methyldopa.
- ARBs (losartan, valsartan): Same risks as ACE inhibitors.
- Statins: Stop before conception; theoretical concerns about fetal cholesterol synthesis.
- SGLT2 inhibitors: Stop before conception; insufficient human data and animal toxicity.
- GLP-1 receptor agonists: Stop 1 to 2 months before conception attempts (longer for tirzepatide due to half-life); insufficient human safety data.
- DPP-4 inhibitors: Stop; limited safety data.
- Sulfonylureas (glipizide, glimepiride, glyburide): Switch to insulin. Glyburide associated with maternal hypoglycemia and neonatal complications.
- Thiazolidinediones (pioglitazone): Stop.
- Meglitinides: Limited data; usually switched.
Medications That Continue
- Insulin: Gold standard. All major analogs (aspart, lispro, detemir, glargine, NPH) considered acceptable.
- Metformin: Often continued, especially in T2D. See the MiTy trial discussion in our pregnancy with type 2 diabetes article.
- Thyroid medication: Continue; dose often increases in pregnancy.
- Aspirin (low-dose): Often started at 12 to 16 weeks for preeclampsia prevention.
Complication Screening
Eyes
- Dilated retinal exam before pregnancy
- Rapid A1C lowering can transiently worsen retinopathy — gradual improvement preferred
- Pre-existing retinopathy can progress during pregnancy
- Treat significant retinopathy before conception when possible
Kidneys
- UACR (urine albumin-to-creatinine ratio), creatinine, eGFR
- Microalbuminuria may worsen in pregnancy
- Significant proteinuria raises preeclampsia and growth restriction risk
- Stage 3+ CKD complicates pregnancy substantially — discuss with nephrology and MFM
Thyroid
- TSH, free T4
- Women with T1D often have autoimmune thyroid disease
- Hypothyroidism (even mild) affects fetal brain development
- Target TSH below 2.5 in first trimester
- Levothyroxine doses often need to increase 25 to 50 percent in pregnancy
Cardiovascular
- Blood pressure assessment and treatment
- Lipid panel (statin stopped before conception)
- EKG if longer-duration diabetes
- Cardiology consultation if cardiovascular disease established
Other
- Hemoglobin/iron studies
- B12 if on long-term metformin
- Vitamin D level
- Vaccination status: rubella, varicella, hepatitis B, flu, Tdap, COVID
- Sleep apnea screening (more common in T2D, worsens in pregnancy)
The Reproductive Life Plan
ADA Section 15 recommends that reproductive life plan discussions begin in adolescence for women with diabetes and continue at every routine visit until pregnancy is desired. The conversation covers:
- Do you want to have children?
- When do you think you might want to start trying?
- How many children do you imagine?
- What contraception are you using or planning?
- How is your diabetes control currently?
- What would help you reach pregnancy goals?
This is not a one-time conversation. Goals change. The point is to ensure planning happens — that no pregnancy in a woman with diabetes is unplanned and unprepared if it can be avoided.
Contraception with Diabetes
- Reliable contraception until A1C is at target and the woman is ready
- Most contraceptive methods are safe in diabetes
- Long-acting reversible contraception (LARC — IUDs, implants) is highly effective
- Combined hormonal contraception generally safe in uncomplicated diabetes; avoid in vascular complications
- Progestogen-only methods safe in most cases
- Emergency contraception is safe and effective
- See companion article on birth control and diabetes
Lifestyle Optimization Before Conception
- Weight: Optimize before conception when possible. Modest weight loss in overweight women improves fertility and pregnancy outcomes. Avoid extreme dieting close to conception.
- Smoking: Cessation before conception. Smoking is teratogenic and worsens diabetic vascular complications.
- Alcohol: Cessation before conception attempts.
- Substance use: Address before pregnancy.
- Exercise: Build a sustainable routine before pregnancy — easier to maintain than to start during pregnancy.
- Nutrition: Mediterranean-style pattern, adequate protein, see diet and nutrition
- Sleep: Treat sleep apnea, optimize sleep hygiene
- Mental health: Address depression, anxiety, eating disorders before pregnancy
Building the Team
| Specialist | Role |
|---|---|
| Endocrinologist or PCP with diabetes expertise | A1C optimization, medication management |
| Maternal-fetal medicine (MFM) specialist | High-risk OB care; ideally meet before conception |
| Certified diabetes care and education specialist (CDCES) | Insulin titration, CGM/pump education, sick-day rules |
| Registered dietitian | Carb counting, weight, pregnancy nutrition |
| Ophthalmologist | Retinal exam, treatment of retinopathy |
| Nephrologist (if CKD) | Kidney function optimization |
| Cardiologist (if established CV disease) | Risk stratification for pregnancy |
| Mental health provider | Address mood, eating disorders, diabetes distress |
A Realistic Timeline
- 6 months before: Start preconception visits; review medications; complication screening; build folate stores; address weight, smoking
- 3 months before: Medication switches complete; A1C target approached; vaccinations updated; reliable contraception in place
- 1 month before: A1C at target; team ready; trying to conceive
- Pregnancy confirmed: Immediately notify endocrinology and OB; first MFM visit within 2 to 4 weeks
Special Situations
- Unplanned pregnancy: Notify endocrinology immediately; rapid medication review; do not stop insulin; folate started immediately
- Older maternal age (≥35): Genetic counseling discussion; closer monitoring
- Prior adverse pregnancy outcome: Detailed review; aspirin from 12 weeks; closer monitoring
- Multiple comorbidities: Cardiology, nephrology, MFM coordination
- Established retinopathy or nephropathy: Optimize before conception; close in-pregnancy monitoring
- Recent bariatric surgery: Wait 12 to 24 months before conceiving; nutritional optimization
- Recent GLP-1 use: Allow medication clearance before conception
When to Seek Specialist Input
- Considering pregnancy in the next 6 to 12 months
- A1C above 6.5 percent and trying to conceive
- On medications that need to be stopped before pregnancy
- Complications (retinopathy, nephropathy, hypertension)
- Difficulty conceiving
- Prior adverse pregnancy outcome
- Unplanned pregnancy — immediately
For pregnancy-specific guidance see our companion articles on pregnancy with type 1 diabetes, pregnancy with type 2 diabetes, insulin during pregnancy, normal glucose levels in pregnancy, and high blood sugar during pregnancy effects on baby.
The Bottom Line
Preconception diabetes care substantially reduces risks of congenital anomalies, miscarriage, and other adverse pregnancy outcomes — the first 6 to 10 weeks of fetal development are most sensitive to maternal glucose, and most major organs form before many women know they are pregnant. The foundation is A1C below 6.5 percent before conception (some specialists target below 6.0 percent), folate 400 to 1000 mcg daily, medication review with stopping of ACE/ARB/statins/SGLT2/GLP-1 agents and switching most oral diabetes medications to insulin, complication screening (eyes, kidneys, thyroid), and reliable contraception until target is reached. Reproductive life plan discussions should begin in adolescence for women with diabetes. Building a multidisciplinary team — endocrinologist, MFM, diabetes educator, ophthalmologist, sometimes nephrology and cardiology — and starting 3 to 6 months before trying to conceive gives the best foundation for a healthy pregnancy. Talk to your endocrinologist and consider a maternal-fetal medicine consultation before pregnancy, not after.
