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Metformin

Biguanide Antidiabetic Agent

FDA Category B (No Fetal Risk in Human/Animal Studies) FDA Category B & ACOG Endorsed
Safe — ACOG / ADA Endorsed for GDM & PCOS

Metformin (Glucophage) is FDA Category B and widely used for Gestational Diabetes Mellitus (GDM) and Polycystic Ovary Syndrome (PCOS). While insulin remains first-line, metformin is a safe and effective oral alternative.

Medical Disclaimer: This report is for educational and informational purposes only. It does not replace professional medical advice. Always consult your healthcare provider before making any medication decisions during pregnancy.
Pregnancy Summary
Clinical overview for pregnancy

Metformin crosses the placenta but has not been shown to increase major birth defect rates. ACOG and ADA endorse its use for GDM when insulin is not feasible.

Trimester Safety Timeline
Safety profile across all three trimesters
1st Trimester
Weeks 1 – 12
Safe / PCOS Use

Often continued in women with PCOS through 12 weeks to reduce early pregnancy loss.

2nd Trimester
Weeks 13 – 27
Safe

Effective for GDM glycemic control. Monitor blood glucose closely.

3rd Trimester
Weeks 28 – Birth
Safe

May require supplemental insulin in late 3rd trimester as insulin resistance peaks.

Placental Transfer
Does this medication cross the placenta?
Crosses Placenta
Yes
Transfer Extent
High (Crosses placenta readily; umbilical cord blood levels equal or exceed maternal levels)

Fetal exposure occurs without adverse effect on structural embryonic organogenesis.

Fetal Risk Assessment
Potential effects on the developing fetus
No Major Teratogenicity

Meta-analyses demonstrate no elevated risk of major structural birth defects compared to insulin or general population.

Maternal Risk Assessment
Potential maternal side effects during pregnancy
Gastrointestinal Side Effects

Nausea, abdominal cramping, and diarrhea. Taking with meals reduces GI distress.

Clinical Recommendation
Professional prescribing guidance
Preferred Oral Choice for GDM

Indicated for GDM and type 2 diabetes when insulin is declined or unavailable, or for PCOS.

If Already Taken
"I took this before knowing I was pregnant"
1
Do Not Discontinue Abruptly

Maintain blood glucose control and consult your endocrinologist/OB-GYN.

Pregnancy Monitoring Protocol
Recommended follow-up and surveillance
Glycemic & Fetal Surveillance
  • Fasting & postprandial blood glucose monitoring
  • Fetal growth ultrasound in 3rd trimester
Safer Alternatives
Active ingredients with better pregnancy safety profiles
insulin
Gold standard antidiabetic in pregnancy (does not cross placenta).
Safe
Professional Clinical Notes
Key prescribing considerations and clinical pearls
  • ACOG Practice Bulletin #201: Insulin is first-line, but metformin is a reasonable alternative for GDM.
Patient-Friendly Explanation
In simple, easy-to-understand language
Easy to Understand

Metformin (Glucophage) is commonly used to treat gestational diabetes and PCOS during pregnancy. It helps control blood sugar safely.

Frequently Asked Questions
Common questions about Metformin in pregnancy

Yes, metformin crosses the placenta, but extensive studies show it does not increase the risk of birth defects.

Evidence Level
Quality of available safety data
FDA Category B & ACOG Endorsed

Endorsed by ACOG and American Diabetes Association guidelines.

References & Primary Sources
Official U.S. Food & Drug Administration (FDA) PLLR & ACOG Clinical Database
All pregnancy safety evaluations, risk categories, and drug monographs are compiled directly from U.S. FDA Pregnancy and Lactation Labeling Rule (PLLR) standards and approved FDA prescribing labels.
  1. 1
    U.S. Food and Drug Administration (FDA) PLLR — FDA Pregnancy and Lactation Labeling Rule & Approved Prescribing Information Database Last updated: Official FDA Standard
  2. 2
    FDA Center for Drug Evaluation and Research (CDER) — FDA MedWatch & Black Box Warning Database Last updated: Official FDA Standard
  3. 3
    ACOG Practice Bulletins & Guidelines — American College of Obstetricians and Gynecologists Clinical Recommendations Last updated: 2025 Clinical Edition
  4. 4
    Briggs Drugs in Pregnancy and Lactation — Reference Guide to Fetal and Neonatal Risk (12th Edition) Last updated: 2025 Clinical Edition
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