Diabetes Medications During Pregnancy: Insulin vs. Oral Options Explained

Managing Diabetes During Pregnancy Isn’t Optional - It’s Essential

If you’re pregnant and have diabetes - whether it’s type 1, type 2, or gestational - your blood sugar targets aren’t the same as they were before. Your body is changing fast. Your baby’s developing organs are extremely sensitive to glucose levels. Too high, and you risk having a baby too large for gestational age, neonatal hypoglycemia, or even birth defects. Too low, and you risk dangerous maternal hypoglycemia. The goal? Keep fasting glucose under 95 mg/dL, and under 120 mg/dL two hours after meals. These aren’t suggestions. They’re clinical standards from the Endocrine Society’s 2023 guidelines.

Insulin Is Still the Gold Standard - Here’s Why

Insulin doesn’t cross the placenta. That’s the biggest reason it’s the first-line treatment for all types of diabetes during pregnancy. It’s been used for decades. It’s been studied in hundreds of thousands of pregnancies. And it’s safe. No link to birth defects. No long-term fetal risks shown in follow-up studies.

Not all insulins are equal here. Rapid-acting analogs like insulin lispro and insulin aspart are preferred over regular human insulin because they act faster and clear quicker after meals. That means less risk of low blood sugar later in the day. Long-acting options? Insulin detemir and insulin glargine have solid safety data from observational studies involving over 700 pregnant women. Both perform just as well as older NPH insulin, with fewer nighttime lows.

But avoid insulin glulisine and insulin degludec. There’s just not enough data. The Joslin Diabetes Center says outright: don’t use them in pregnancy. If you were on one before getting pregnant, switch before conception.

Insulin pumps (CSII) are increasingly common. Studies show they help lower HbA1c and reduce total insulin needs by delivery. But they don’t magically improve birth outcomes over multiple daily injections. The real advantage? More flexibility. You can adjust basal rates as your insulin resistance climbs in the second and third trimesters - which it does, often doubling or tripling.

Metformin: The Controversial Oral Option

Metformin is the only oral medication with enough data to be considered in some cases. It’s not approved by the FDA for gestational diabetes, but it’s used off-label - and often effectively.

Compared to insulin, metformin reduces the risk of having a large baby (LGA), needing NICU care, and developing preeclampsia. A 2019 NIH meta-analysis showed a 35% lower chance of LGA births with metformin. It’s also easier to take. No needles. Fewer lows. Cheaper.

But here’s the catch: about half of women on metformin end up needing insulin anyway. Glucose control often falls short in the third trimester. And metformin crosses the placenta. The baby’s exposed to levels similar to the mother’s. That raises concerns about long-term metabolic effects - like whether it alters the mTOR pathway, which regulates fetal growth and cell metabolism.

That’s why the Endocrine Society (2023) says: don’t add metformin to insulin for women with preexisting type 2 diabetes. The benefit of fewer large babies doesn’t outweigh the risk of smaller babies (SGA). And Joslin’s 2022 guidelines go further: they say metformin shouldn’t be used beyond the first trimester - period.

So where does that leave you? If you’re diagnosed with gestational diabetes and diet isn’t enough, metformin can be a reasonable first step - especially if you’re terrified of injections. But you need to know: you might still need insulin later. And you need to be monitored closely.

What About Other Oral Drugs? Don’t Risk It

GLP-1 receptor agonists like semaglutide or liraglutide? Stop them before you even try to get pregnant. The Endocrine Society says clearly: discontinue before conception. There’s no safe window. Animal studies show potential harm, and human data is too thin to justify risk.

SGLT2 inhibitors (like dapagliflozin)? DPP-4 inhibitors (like sitagliptin)? Alpha-glucosidase inhibitors (like acarbose)? All lack safety data. None are recommended. The Joslin guidelines call them “unacceptable” in pregnancy.

And while you’re at it - don’t assume that because a drug is safe for non-pregnant adults, it’s safe for you now. Pregnancy changes how your body absorbs, processes, and eliminates drugs. What worked last year might be dangerous this year.

Preconception Planning Is Half the Battle

If you have type 1 or type 2 diabetes and are thinking about getting pregnant, you’re not starting from zero. You’re starting from a critical prep phase.

The OHSU Diabetes and Pregnancy Program recommends an HbA1c under 6.5% before conception. If yours is above 10%, they strongly advise against pregnancy until you get it under control. Why? Because the first eight weeks of pregnancy - when the baby’s heart, brain, and spine are forming - happen before most people even know they’re pregnant. High glucose during that time increases the risk of serious birth defects by up to 10 times.

That’s why long-acting reversible contraception (LARC) is often offered to women with poorly controlled diabetes. It’s not about saying no to motherhood. It’s about giving you time to get your numbers right - so when you do get pregnant, you’re giving your baby the best shot.

Also: start taking low-dose aspirin (81-100 mg daily) at 12 weeks. It’s not just for heart health. For women with preexisting diabetes, it cuts preeclampsia risk by about 25%. That’s backed by ACOG, Joslin, and OHSU.

What Happens During Labor and After Delivery?

During labor, your blood sugar will be checked every hour. You might get IV insulin if it spikes. Your team will watch your baby’s heart rate closely - high glucose can stress the baby. After delivery, insulin needs drop sharply - often to 50% or less of your prepregnancy dose. Don’t be surprised if you need way less.

And here’s good news: if you had gestational diabetes, you can usually stop all medications right after birth. Your body resets. Metformin? Gone. Insulin? Gone. Your doctor will check your blood sugar 6-12 weeks postpartum to make sure it’s back to normal. But you’re not off the hook. Women who’ve had gestational diabetes have a 50% chance of developing type 2 diabetes within 10 years. Keep eating well. Stay active. Get screened yearly.

Continuous Glucose Monitors (CGMs): Helpful, But Not Required

CGMs are great. They show trends, not just snapshots. You’ll see how your glucose responds to meals, stress, or sleep. For women with type 1 diabetes, studies show better outcomes with CGM use - fewer highs, fewer lows, healthier babies.

But for type 2 or gestational diabetes? The evidence isn’t strong enough to say CGM is better than fingerstick testing. The Endocrine Society says there’s “lack of direct evidence” supporting CGM superiority for T2DM in pregnancy. That doesn’t mean don’t use one - if you’ve been on it before and find it helpful, keep it. But don’t feel pressured to buy one just because it’s trendy.

Bottom Line: What You Need to Know

• Insulin is the safest, most reliable option - and it’s still the standard.
• Metformin can be used in gestational diabetes, but you might need insulin later - and it’s not for everyone.
• Stop GLP-1 agonists before conception. Avoid all other oral diabetes drugs.
• Get your HbA1c under 6.5% before getting pregnant. If it’s over 10%, delay pregnancy and get help.
• Start low-dose aspirin at 12 weeks to reduce preeclampsia risk.
• After delivery, most gestational diabetes meds stop. But your risk of type 2 diabetes doesn’t.

Managing diabetes during pregnancy is hard. It’s not just about pills or shots. It’s about planning, patience, and precision. But with the right team - your OB, endocrinologist, and diabetes educator - you can have a healthy pregnancy and a healthy baby. You’re not alone. And you’re not powerless.