Gestational diabetes in the third trimester
In the third trimester, the resistance to insulin that causes gestational diabetes keeps growing, so readings can rise and your plan may change. You may also have extra checks on the baby, usually from 32 to 34 weeks. Learn your baby's usual pattern of movement, and call right away if it changes.
Why readings can go up now
The ADA says resistance to insulin grows through the second and third trimesters.1 So a plan that kept you in range earlier may need a change. ACOG says some people need medicine even with diet changes and exercise.2 If your readings start to rise, tell your team instead of waiting for the next visit. More on insulin for gestational diabetes.
Extra checks on the baby
With gestational diabetes you have more prenatal visits, and special tests may be needed to check the baby's well-being:2
| Check | What it is |
|---|---|
| Kick counts | You keep a record of how often you feel the baby move. A healthy baby tends to move about the same amount each day.2 |
| Nonstress test | A belt with a sensor on your belly records the baby's heart rate as the baby moves. Nothing is done to stress the baby.2 |
| Biophysical profile (BPP) | The same heart rate check plus an ultrasound, which estimates the fluid around the baby and checks breathing, movement and muscle tone.2 |
When these tests are needed, they usually start between 32 and 34 weeks. How often you have them depends on why they are done.3
Your baby's movements
- There is no set number of movements that is normal. Learn your own baby's pattern.4
- If the baby moves less than usual, or the pattern changes, contact your midwife, ob-gyn or maternity unit right away. Never go to sleep with a change you have not reported, and do not rely on a home heartbeat monitor.42
- If it feels like an emergency, call 911.
When the baby comes
If food and activity keep you in range, ACOG advises birth between 39 weeks and 40 weeks plus 6 days. If you take medicine for it, ACOG advises birth during week 39.5 See induction and birth with gestational diabetes and your baby after birth.
Labor before 37 weeks is preterm labor. Its signs include a change in vaginal discharge, pressure low in the belly or pelvis, a constant dull low backache, regular tightening or contractions (often painless), and your water breaking. If you have any of them, call your ob-gyn right away; do not wait.6
Other signs to know
ACOG says preeclampsia is more common with gestational diabetes.2 Know its warning signs: preeclampsia signs.
A short list for these weeks
- Keep checking and recording your blood sugar, and bring the record to every visit.2 First Fork makes a one-page PDF report of your readings for the clinic.
- Ask your team: when is the birth planned, what happens with your medicine in labor, and how is the baby's blood sugar checked after birth?
Questions
Why is my blood sugar going up in the third trimester?
The ADA says resistance to insulin grows through the second and third trimesters. Tell your team; your plan may need a change.
How often should my baby move in the third trimester?
There is no set number. Learn your baby's usual pattern, and contact your maternity unit or ob-gyn right away if it slows down or changes.
What tests will I have in the third trimester with gestational diabetes?
You may have kick counts, nonstress tests or a biophysical profile. When they are needed, they usually start between 32 and 34 weeks.
When will I deliver with gestational diabetes?
ACOG advises between 39 weeks and 40 weeks plus 6 days if food and activity keep you in range, and during week 39 if you take medicine for it.
Sources
- American Diabetes Association. 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2026. Diabetes Care 2026;49(Suppl. 1):S321. https://pmc.ncbi.nlm.nih.gov/articles/PMC12690181/
- ACOG. Gestational Diabetes (FAQ 177, reviewed April 2026). https://www.acog.org/womens-health/faqs/gestational-diabetes
- ACOG. Special Tests for Monitoring Fetal Well-Being (patient FAQ). https://www.acog.org/womens-health/faqs/special-tests-for-monitoring-fetal-well-being
- Royal College of Obstetricians and Gynaecologists (UK). Your baby's movements in pregnancy (patient information). https://www.rcog.org.uk/for-the-public/browse-our-patient-information/your-babys-movements-in-pregnancy/
- ACOG Practice Bulletin No. 190: Gestational Diabetes Mellitus. Obstet Gynecol 2018;131:e49–e64 (reaffirmed 2026). https://pubmed.ncbi.nlm.nih.gov/29370047/
- ACOG. Preterm Labor and Birth (patient FAQ). https://www.acog.org/womens-health/faqs/preterm-labor-and-birth
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