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DIABETES SERIES · ARTICLE 14 OF 17
Diabetes and pregnancy
What to know before, during, and after.
Pregnancy is one of the most common times someone first discovers they have a problem with blood sugar. Sometimes it's gestational diabetes — a temporary form that develops during pregnancy and usually goes away after birth. Sometimes it's pre-existing diabetes that needs different management because of the baby. Either way, the rules of the game change for nine months.
The good news: with proper care, women with diabetes in South Africa have safe pregnancies and healthy babies every single day. The numbers used to be much worse. Modern monitoring, careful blood sugar control, and good clinic teams have changed that.
This article walks through the three situations: planning a pregnancy when you already have diabetes, managing diabetes during pregnancy, and what happens after.
Before you read on
This article is for women planning a pregnancy with pre-existing diabetes, women newly diagnosed with gestational diabetes, and the family members supporting them. If any of this applies, the most important step is being booked into an antenatal clinic early — ideally before week 12.
Gestational diabetes — what it is
Gestational diabetes (GDM) is diabetes that develops during pregnancy in a woman who didn't have it before. It usually appears around weeks 24 to 28, when pregnancy hormones make the body more resistant to insulin. The pancreas can't keep up, blood sugar rises, and the woman is diagnosed at her routine screening.
About 7–10% of pregnancies are affected in South Africa, though the rate varies by population. Risk is higher if you are over 35, overweight, have a family history of Type 2 diabetes, have polycystic ovary syndrome, or had GDM in a previous pregnancy.
How it's diagnosed
Most pregnant women in South Africa are screened with an Oral Glucose Tolerance Test (OGTT) between weeks 24 and 28. You drink a sugary solution, then blood is tested at intervals to see how your body handles it. The clinic uses the results to diagnose.
If you have strong risk factors, the OGTT may be done earlier — sometimes at the booking visit.
What happens after diagnosis
The treatment ladder for GDM looks like this:
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Step 1 — food and movement. About 70% of women with GDM control it through diet and exercise alone. Smaller portions of starch, more vegetables, walking after meals.
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Step 2 — metformin. If diet alone isn't enough, metformin is usually added. Safe in pregnancy.
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Step 3 — insulin. The most effective option when needed. Insulin doesn't cross the placenta, so it's safe for the baby. Many women need insulin in the third trimester even if they didn't earlier.
Pre-existing diabetes — planning a pregnancy
If you have Type 1 or Type 2 diabetes and want to become pregnant, the single most important window is the three to six months BEFORE conception. Blood sugar control during this period determines a lot about the baby's early development.
Pre-pregnancy planning typically includes:
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Getting HbA1c below 6.5% if possible (clinic will set your target)
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Reviewing medication — some tablets and statins must be stopped before conception; insulin is usually continued or started
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Folic acid 5 mg daily for at least 3 months before conception (higher than the standard 0.4 mg dose for non-diabetics)
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Eye exam — pregnancy can worsen retinopathy
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Kidney function check
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Blood pressure check and any medication adjustments
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Thyroid screening (Type 1 diabetics)
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Dental check — gum disease worsens in pregnancy
Why pre-conception control matters
The baby's organs form in the first 8 weeks of pregnancy — often before a woman even knows she's pregnant. High blood sugar during this window raises the risk of birth defects significantly.
Women with well-controlled diabetes before and during early pregnancy have a risk of birth defects close to that of women without diabetes. Women with poorly controlled diabetes have several times that risk.
This is the strongest argument for planned pregnancies if you have pre-existing diabetes — and for tight control as soon as you know.
During pregnancy — the targets change
Once pregnant, the blood sugar targets are tighter than at any other time in life. The goal is to keep glucose close to normal throughout the day.
Measurement Target during pregnancy Fasting glucose Under 5.3 mmol/L 1 hour after meals Under 7.8 mmol/L 2 hours after meals Under 6.7 mmol/L HbA1c (first trimester) Under 6.5% HbA1c (third trimester) Under 6.0% if achievable safely
Hitting these targets usually requires more testing than usual — often 4 to 7 finger-pricks a day. Continuous glucose monitoring (CGM) is increasingly recommended for Type 1 pregnancies and is sometimes covered by medical aid.
What to eat
Pregnancy with diabetes needs a balanced diet that supports the baby's growth without spiking blood sugar. The basics:
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Three meals plus 2–3 small snacks per day — avoid going more than 3 hours without eating
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Smaller portions of starch (the fist rule from article 4) at each meal
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Protein at every meal — eggs, beans, dairy, meat or fish
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Vegetables fill half the plate
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Fruit limited to 2–3 servings a day, spread out, with protein or fat alongside
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Avoid sugary drinks and obvious sugary foods completely during pregnancy
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Folic acid, iron and calcium supplements as prescribed
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Avoid raw fish, soft cheese, and undercooked meat for usual pregnancy food-safety reasons
Risks if blood sugar isn't controlled
This list is not meant to scare. It's meant to make clear why the work matters.
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Macrosomia (very large baby). Excess glucose crosses to the baby, the baby's pancreas releases extra insulin, and the baby grows large. Makes vaginal delivery difficult and raises caesarean risk.
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Neonatal hypoglycaemia. The baby is born used to high glucose; suddenly cut off, the baby's own insulin can push them low. Easily managed if the team knows to watch for it.
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Premature delivery. Risk is higher with uncontrolled diabetes.
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Pre-eclampsia. High blood pressure + protein in the urine in pregnancy. Diabetes raises this risk; control lowers it.
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Stillbirth. Risk is higher with poor control, especially in the third trimester.
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Birth defects. Only relevant for pre-existing diabetes — established in the first 8 weeks.
Delivery and what comes next
Most women with well-controlled diabetes can plan a normal vaginal delivery. Some will be advised to deliver by caesarean if the baby is very large, if there are complications, or if labour is induced and progresses slowly.
Day of delivery:
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Insulin needs change dramatically once the placenta is delivered — sometimes dropping to near zero
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Blood sugar is monitored every 1–2 hours during labour
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The baby's blood sugar is tested at 1, 4, and 12 hours after birth (and longer if needed)
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Breastfeeding lowers maternal blood sugar — many women's medication needs drop while feeding
After birth — for women with gestational diabetes
Most women see blood sugar normalise within days of delivery. But:
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Get a glucose tolerance test 6–12 weeks after delivery to confirm normalisation
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Women with GDM have a 50% lifetime risk of developing Type 2 diabetes — most within 10 years
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Reduce that risk: maintain a healthy weight, stay active, eat well, get screened annually
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Future pregnancies have a 30–60% recurrence rate of GDM — plan accordingly
After birth — for women with pre-existing diabetes
Insulin needs typically drop significantly. Type 1 women may need 30–50% less than during pregnancy. Type 2 women may go back to tablets if they were on insulin only for the pregnancy.
Breastfeeding is encouraged. It helps with weight loss, reduces future Type 2 risk in the baby, and lowers maternal blood sugar. Watch for hypos during feeding sessions and especially at night.
Breastfeeding and diabetes
Some practical things to know:
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Breastfeeding burns 1500–2000 kJ a day — your blood sugar will run lower
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Have a snack or fast sugar nearby before night feeds
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Most diabetes medications are safe while breastfeeding — check each one with the clinic
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Insulin doesn't pass to the baby through breast milk
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Stay well hydrated — milk production needs fluid, and high blood sugar makes dehydration easier
The Phila Today pregnancy checklist
Take this list to your clinic visit, or pin it up at home.
Stage To do 3–6 months before pregnancy HbA1c \<6.5%, folic acid 5 mg daily, medication review, eye exam, kidney check, BP review Weeks 1–12 Confirm pregnancy, book antenatal early, continue folic acid, intensify monitoring Weeks 12–24 Tight blood sugar control, OGTT if at risk, normal antenatal visits Weeks 24–28 OGTT for screening if not done; diagnose GDM if present Weeks 28–36 More frequent monitoring, insulin often needed or increased Weeks 36–40 Plan delivery with the team, prepare for hospital admission Delivery Frequent monitoring; baby's sugar checked at birth 6–12 weeks postnatal OGTT for women who had GDM; insulin adjustment for pre-existing diabetes Going forward Annual screening if GDM; continued chronic care for pre-existing diabetes
The bigger picture
Diabetic pregnancy is more demanding than non-diabetic pregnancy. There are more tests, more medication adjustments, more careful eating. It is also entirely possible to have a safe pregnancy and a healthy baby — and tens of thousands of South African women do every year.
The single biggest thing that determines a good outcome is being inside the system early. Antenatal clinic booking before week 12, an HbA1c that's already controlled, a team that knows you. Everything else follows from there.
The next article in the series takes a different turn entirely — a deeper dive into mental health and diabetes, because the topic deserves more than a paragraph in another article. Burnout, anxiety, depression, and the underestimated psychological weight of long-term diabetes.
Where to get more help
Diabetes South Africa — diabetessa.org.za · 011 792 9888
Antenatal clinic — book your first visit as soon as you know you're pregnant
Phila Today Eat tab — many of the recipes are pregnancy-friendly
Phila Today Diabetes Series — next: mental health and diabetes
Phila Today · Article 14 of 17 in the Diabetes Series