ConditionWomen's & pregnancy health
Pregnancy With Pre-existing Diabetes
Pregnancy in diabetes refers to pregnancy in someone who already has type 1 or type 2 diabetes before conceiving (pregestational diabetes), as opposed to gestational diabetes, which starts during pregnancy. High blood sugar around conception and early pregnancy raises the risk of miscarriage and birth defects, and later in pregnancy it can cause a large baby, preeclampsia and stillbirth. With planning before pregnancy and tight, safe blood sugar control, most people with diabetes have healthy pregnancies and babies.
Also called: Pregestational diabetes, pre-existing diabetes in pregnancy, diabetes and pregnancy
At a glance
- What it is
- Pregnancy in someone with type 1 or type 2 diabetes from before conception.
- Key message
- Plan ahead. Good control before and in early pregnancy lowers the risk of birth defects and miscarriage.
- Preconception target
- HbA1c below 6.5 percent if it can be reached safely.
- Pregnancy targets
- Fasting below 95 mg/dL (5.3 mmol/L), 1 hour after meals below 140 mg/dL (7.8 mmol/L), 2 hours below 120 mg/dL (6.7 mmol/L).
- Care
- Insulin is the main medicine, plus extra eye, kidney and fetal checks, and low-dose aspirin for preeclampsia prevention.
When to get help
Call 911 or go to the ER
- Nausea, vomiting, belly pain, fast breathing or fruity breath, even with only modestly high blood sugar (possible diabetic ketoacidosis, which can occur at lower glucose levels in pregnancy)
- Severe low blood sugar with confusion, seizures or unconsciousness
- Severe headache, vision changes or upper belly pain after 20 weeks
See a doctor within a day or two
- Repeated low blood sugars, or high readings that do not come down with your usual adjustments
- Vomiting and unable to keep food or insulin plan on track
- Baby moving less than usual after about 24 weeks
- Blood pressure of 140/90 or higher
Book a routine appointment
- Planning a pregnancy with diabetes: book a preconception visit
- A positive pregnancy test: contact your diabetes and obstetric teams straight away
Why diabetes matters in pregnancy
The baby's organs form in the first 8 to 10 weeks, often before a pregnancy is known. High blood sugar during this time increases the risk of:
- miscarriage
- birth defects, especially of the heart, spine and brain
Later in pregnancy, glucose crosses the placenta. The baby makes extra insulin and grows larger, which can lead to:
- a large baby (macrosomia) and birth injuries, including shoulder dystocia
- too much amniotic fluid
- low blood sugar, breathing problems and jaundice in the newborn
- stillbirth
- preterm birth
For the mother, risks include preeclampsia, worsening of diabetic retinopathy and kidney disease, low blood sugar episodes, ketoacidosis and cesarean delivery.
Planning before pregnancy
Ideally, start planning 3 to 6 months before trying to conceive:
- blood sugar: aim for HbA1c below 6.5 percent if safely achievable, without frequent lows
- folic acid: start before conception. People with diabetes are often advised to take a higher dose than usual, so ask your doctor
- review medicines: stop ACE inhibitors, ARBs and statins before or as soon as pregnancy is confirmed, and switch to pregnancy-safe alternatives. Many non-insulin diabetes medicines, including GLP-1 receptor agonists and SGLT2 inhibitors, are stopped
- eye exam for retinopathy
- kidney tests: creatinine and urine protein
- thyroid tests in type 1 diabetes
- blood pressure control
- effective contraception until you are ready
During pregnancy
Blood sugar management
- insulin is the preferred medicine for both type 1 and type 2 diabetes in pregnancy. Needs change: they may drop in the first trimester, then rise steeply in the second and third
- metformin is sometimes used in type 2 diabetes, but it crosses the placenta, and insulin is usually needed as well
- continuous glucose monitoring (CGM) improves outcomes in type 1 diabetes and is widely recommended
- insulin pumps and automated insulin delivery systems can help
- check blood sugar frequently: fasting and after meals, and overnight if needed
- HbA1c target: below 6 percent in pregnancy if achievable without significant lows, or below 7 percent if needed to avoid lows
Preventing and treating lows
Low blood sugar is more common in early pregnancy, especially in type 1 diabetes, and awareness of lows can drop. Always carry fast-acting glucose, and make sure your partner knows how to use glucagon.
Extra checks
- eye exams in each trimester and for a year after birth
- kidney function and urine protein
- blood pressure at every visit
- low-dose aspirin from about 12 weeks to lower the risk of preeclampsia
- ultrasounds: a detailed anatomy scan and fetal heart scan (echocardiogram), and growth scans in the third trimester
- fetal monitoring in late pregnancy
Labor and birth
- delivery is often planned between about 36 and 39 weeks, depending on blood sugar control and complications
- vaginal birth is often possible. Cesarean may be advised for a very large baby or other reasons
- blood sugar is monitored closely during labor, often with an insulin and glucose drip
After birth
- insulin needs drop sharply right after delivery. Doses are reduced to avoid lows
- the baby's blood sugar is checked in the first hours, and early feeding is encouraged
- breastfeeding is encouraged and can lower blood sugar, so have snacks nearby
- resume or adjust medicines, choosing breastfeeding-safe options
- discuss contraception and planning for any future pregnancy
Gestational diabetes vs pre-existing diabetes
| Pre-existing (type 1 or 2) | Gestational diabetes | |
|---|---|---|
| When it starts | Before pregnancy | Usually second or third trimester |
| Risk of birth defects | Increased if poorly controlled early | Not increased |
| After birth | Diabetes continues | Usually resolves, but future type 2 diabetes risk is higher |
Frequently asked questions
Can I have a healthy pregnancy with type 1 diabetes?
Yes. With planning before conception, close blood sugar control using insulin and continuous glucose monitoring, and regular checks by diabetes and obstetric teams, most people with type 1 diabetes have healthy pregnancies and babies.
What are blood sugar targets in pregnancy?
Common targets are fasting below 95 mg/dL (5.3 mmol/L), 1 hour after meals below 140 mg/dL (7.8 mmol/L), and 2 hours after meals below 120 mg/dL (6.7 mmol/L), with HbA1c ideally below 6 percent if this can be reached without frequent lows. Your team will personalize targets.
Can I take metformin while pregnant?
Metformin is sometimes used in type 2 diabetes during pregnancy, but it crosses the placenta, and many people need insulin as well. Insulin is the preferred medicine. Discuss your plan with your doctor before or as soon as you become pregnant.
Why is my insulin dose changing so much during pregnancy?
In early pregnancy, insulin needs often fall and lows are common. From the second trimester, placental hormones increase insulin resistance, so doses often double or more by the third trimester. After birth, needs drop quickly.
Sources
This guide was written from current patient and clinical guidance, including:
- American Diabetes Association: Standards of Care in Diabetes, Management of Diabetes in Pregnancy
- American College of Obstetricians and Gynecologists: Pregestational Diabetes Mellitus (Practice Bulletin 201)
- NICE: Diabetes in pregnancy, management from preconception to the postnatal period (NG3)
- CDC: Diabetes during pregnancy
- March of Dimes: Pre-existing diabetes and pregnancy