Home/Gestational Diabetes
Condition Deep-Dive

Gestational Diabetes

A pregnancy-specific glucose intolerance affecting 5 to 9% of US pregnancies each year, which happens when the body cannot make enough insulin for the extra needs of pregnancy10. Diet and activity come first, with medicine added when blood sugar targets are not met11.

Hormonal & Women's Health Evidence-Based

Last updated:

โš ๏ธ Medication safety: please read first. The nutrition and supplement approaches on this page are meant to work alongside your prescribed treatment, never to replace it. Never stop, reduce or change your diabetes medication or insulin without your prescriber's guidance. Doing so can be dangerous. Several supplements are not safe in pregnancy or can push blood sugar too low, so talk to your prescriber, midwife or pharmacist before starting anything on this page.
Definition

What Is Gestational Diabetes?

Gestational diabetes mellitus (GDM) is glucose intolerance with first onset or first recognition during pregnancy, typically diagnosed in the second or third trimester via an oral glucose tolerance test.

Pregnancy hormones and weight gain make the body's cells use insulin less well, which raises the need for insulin. Gestational diabetes develops when the body cannot make enough, often in women who already had some insulin resistance before pregnancy10.

GDM is classified by management requirements. The classification is not about severity per se; it is about which intervention is needed. The distinction matters for monitoring intensity, delivery timing and postpartum follow-up4. Many GDM cases are class A1, controllable with nutrition and movement alone:

A pregnant uterus with the baby and placenta, and a magnified blood vessel carrying high blood glucose

Class A1: Diet-Controlled GDM (~80%)

Blood glucose is kept in target with nutrition, post-meal walks and sleep optimization alone. Fasting less than 95 mg/dL, 1-⁠hour post-meal less than 140 mg/dL (or 2-⁠hour less than 120 mg/dL). The strong majority of GDM falls into this class and resolves at delivery.

  • โ†’Hallmarks: Glucose targets met without medication; usually milder insulin resistance
  • โ†’Primary lever: Carb-controlled, protein-anchored eating + post-meal walks + adequate sleep
  • โ†’Outcome: Typically delivers at 39 to 40 weeks; usually resolves after the birth, confirmed with a diabetes test 4 to 12 weeks later

Class A2: Medication-Requiring GDM (~20%)

Blood glucose remains above target despite optimal diet and lifestyle, requiring insulin (preferred), metformin or glyburide. More common when GDM is diagnosed early, when BMI is high, or when there is significant prior insulin resistance. Diet remains foundational even when medication is added.

  • โ†’Hallmarks: Persistent fasting > 95 mg/dL or post-meal > 140 mg/dL despite full diet effort
  • โ†’Primary lever: Diet + insulin (basal, mealtime or both); metformin acceptable per OB
  • โ†’Outcome: Delivery typically planned 37 to 39 weeks based on glucose control and growth

Overt / Pre-existing Diabetes Identified in Pregnancy

Glucose abnormalities found at first prenatal visit (HbA1c ≥ 6.5%, fasting ≥ 126 mg/dL, random ≥ 200 mg/dL with symptoms) likely reflect pre-existing type 2 diabetes that was undiagnosed. Carries higher risks of congenital anomalies and requires immediate intensive management.

  • โ†’Hallmarks: Elevated HbA1c at first prenatal visit; classic diabetes symptoms; often BMI > 30
  • โ†’Primary lever: Immediate diet + insulin; tight HbA1c targets; maternal-fetal medicine co-management
  • โ†’Outcome: Diabetes continues postpartum; transition to standard type 2 management

Post-GDM Persistence / Recurrence

A history of GDM identifies a high-risk metabolic phenotype. About half of women with gestational diabetes go on to develop type 2 diabetes10. Postpartum lifestyle is a major influence on long-term outcome4.

  • โ†’Hallmarks: History of GDM; persisting insulin resistance markers postpartum
  • โ†’Primary lever: Lifelong low-glycemic eating, strength training, weight regulation, breastfeeding5
By the Numbers

Gestational Diabetes by the Numbers

5 to 9%
of US pregnancies are affected by gestational diabetes each year10
70 to 85%
of people with GDM can manage it with lifestyle change alone, depending on the population, according to the American Diabetes Association18
About half
of women with gestational diabetes go on to develop type 2 diabetes, which is why testing continues after the birth10
2 to 3ร—
higher risk of macrosomia3 (birthweight over 8 lb 13 oz, 4,000 g) and shoulder dystocia
About 50%
lower incidence of type 2 diabetes with intensive lifestyle change, or with a glucose-lowering tablet, in women with prior GDM and impaired glucose tolerance (DPP trial)19
51%
recurrence of GDM in a later pregnancy, pooled from 31 population-based studies20
Signs & Symptoms

Symptoms of Gestational Diabetes

GDM is mostly silent. Most women feel fine and are diagnosed only by the routine 24-⁠to-⁠28-⁠week OGTT. When symptoms appear, they typically reflect significant hyperglycemia and warrant prompt evaluation, especially in the third trimester.

SymptomWhat happens
Glucose-Driven Symptoms
Excessive Thirst (Polydipsia)A constant need to drink water beyond normal pregnancy thirst. New-onset extreme thirst in pregnancy is not normal and warrants a glucose check.
Frequent Urination (Polyuria)Beyond the normal pregnancy increase from uterine pressure, GDM produces high-volume, frequent urination including overnight. The kidneys spill glucose into the urine, dragging water with it. New severe nocturia warrants a glucose screen.
TirednessTiredness is one of the symptoms of high blood sugar, though it is also common in pregnancy itself12.
Blurred VisionHigh glucose causes the lens of the eye to swell, transiently changing the refractive index. Vision blurs at distance or for reading, often fluctuating with glucose levels. Resolves once glucose normalizes, but is a clue worth checking.
Recurrent Yeast InfectionsVaginal yeast feeds on glucose, and women with poorly controlled GDM commonly develop recurrent or stubborn yeast infections. Worth a glucose screen if you have new or repeated yeast in pregnancy.
Fetal & Pregnancy-Specific Signs
Excessive Fetal Growth (Macrosomia)Maternal hyperglycemia crosses the placenta. The fetus responds by producing extra insulin, which acts as a growth factor. Estimated fetal weight in the 90th percentile or higher, or abdominal circumference disproportionately ahead of head, often points to GDM.
Polyhydramnios (Excess Amniotic Fluid)Hyperglycemic fetuses urinate more, producing increased amniotic fluid (AFI > 24 cm or single deepest pocket > 8 cm). Polyhydramnios on routine ultrasound can be a clue to underlying GDM, though it has many causes.
Recurrent UTIs & Asymptomatic BacteriuriaGlucose in the urine feeds bacteria. Women with GDM have higher rates of UTIs and asymptomatic bacteriuria, which itself raises the risk of pyelonephritis and preterm labor. Universal screening at first prenatal visit catches this.
Preeclampsia & Hypertension RiskGestational diabetes can lead to preeclampsia, which causes high blood pressure in pregnancy; the risks fall when it is found early and well managed12. Watch for new BP elevation alongside any GDM symptoms.
โš ๏ธ Risk-factor red flags: Prior GDM, prior macrosomic baby (over 9 lb (4.1 kg) in CDC guidance; 10 lb (4.5 kg) or more in NHS guidance), prior unexplained stillbirth, BMI > 30, age > 40, PCOS, family history of type 2 diabetes, South Asian, Black, Hispanic, Pacific Islander, Middle Eastern or Indigenous background. Any one of these should mean you are offered screening, and if you have had gestational diabetes before, an earlier test soon after your first prenatal visit12.
Causes

Causes of Gestational Diabetes

Gestational diabetes happens when the body cannot make enough insulin to meet the extra needs of pregnancy; any woman can develop it, and some things make it more likely12.

CauseHow It Contributes to Gestational DiabetesWhat Helps
Pregnancy hormones and insulin resistancePregnancy hormones and weight gain make the body's cells use insulin less well, so the need for insulin rises, and all pregnant women have some insulin resistance late in pregnancy10Checking blood sugar, eating healthy food in the right amounts at the right times, and being active, which lowers blood sugar10; medicine when that is not enough
Insulin resistance before pregnancy, and overweightSome women start pregnancy with insulin resistance and an increased need for insulin; being overweight, or a BMI above 30, raises the risk1012Before pregnancy, losing weight if overweight, a healthy diet and regular activity may help prevent it; during pregnancy, do not try to lose weight10
Gestational diabetes before, or a large babyGestational diabetes in a previous pregnancy, or a previous baby weighing 10 lb (4.5 kg) or more, raises the risk12A diabetes check before the next pregnancy, and an earlier glucose tolerance test soon after your first prenatal visit, repeated at 24 to 28 weeks if normal12
Family history and ethnic backgroundA parent or sibling with diabetes raises the risk, as does South Asian, Black, African-Caribbean or Middle Eastern origin12, and in the US, Hispanic or Latino, American Indian, Alaska Native, Native Hawaiian or Pacific Islander background10Screening: anyone with a risk factor should be offered a glucose tolerance test in pregnancy12
PCOSPolycystic ovary syndrome, a hormone disorder, is a risk factor10Screening in pregnancy, and the PCOS guide on this site for care before pregnancy
Age over 40, and weight-loss surgeryBeing over 40, or having had a gastric bypass or other weight-loss surgery, raises the risk12Screening in pregnancy, as the diagnosis section sets out12
Diagnosis

How Gestational Diabetes Is Diagnosed

All pregnant women in the US are screened at 24 to 28 weeks. High-risk women are screened earlier. Diagnosis is purely lab-based; symptoms are not required.

TestWhat it shows
At-Home Screening
These do not diagnose GDM, but help identify women who should request earlier screening and prepare them for self-monitoring once diagnosed:
Home Glucose Meter (Pre & Post-Diagnosis)A simple finger-stick meter can be used pre-diagnosis to spot-check fasting glucose (target below 95 mg/dL) or 1-⁠hour post-meal (target below 140 mg/dL). Once diagnosed, 4 readings per day (fasting + 1 hour after each meal) is standard.
Food & Glucose DiaryLog every meal and the corresponding 1-⁠hour glucose. Patterns become clear within a week: which carbs spike you, which protein-first combos do not, how walking after meals changes the curve.
Lab & Clinical Tests
Two-Step Screening (Most Common in the US)Step 1: 50-⁠g non-fasting glucose challenge at 24 to 28 weeks. Plasma glucose at 1 hour ≥ 130 to 140 mg/dL (cutoff varies by lab) triggers step 2. Step 2: 100-⁠g 3-⁠hour OGTT, fasting. Two or more values at or above thresholds (fasting 95, 1h 180, 2h 155, 3h 140) confirm GDM1.
One-Step Screening (IADPSG / WHO Criteria)75-⁠g 2-⁠hour OGTT at 24 to 28 weeks, fasting. Any one of the following confirms GDM: fasting ≥ 92 mg/dL, 1 hour ≥ 180 mg/dL or 2 hour ≥ 153 mg/dL.
Early-Pregnancy Glucose ScreeningFor high-risk women at the first prenatal visit: HbA1c (≥ 6.5% suggests pre-existing diabetes), fasting plasma glucose (≥ 126 mg/dL is diagnostic) or 75-⁠g OGTT. Detects pre-existing type 2 diabetes that has been masquerading as GDM and changes management.
Fetal Surveillance Once DiagnosedGrowth ultrasound at 32 to 36 weeks for macrosomia and AFI. Non-stress tests 1 to 2×/week from 32 weeks if class A2 or poorly controlled.
Diabetes Test After the Birth (Critical Step)A blood test after the birth checks whether blood sugar is back to normal: ACOG advises one 4 to 12 weeks after the birth, NICE a fasting glucose test 6 to 13 weeks after, or an HbA1c after 13 weeks14. Often skipped, this is the key follow-up after a GDM pregnancy4. If it is normal, testing continues every year (NICE) or every 1 to 3 years (ACOG).
Treatment Comparison

Conventional and Holistic Treatment for Gestational Diabetes

Nutrition is foundational in both approaches, and both add medicine when targets are not met.

๐ŸŒฟ HOLISTIC
๐Ÿ’Š CONVENTIONAL
๐ŸŒฟ

Holistic / Functional Approach

Low-glycemic, protein-anchored eating + post-meal walks + adequate sleep, in partnership with OB monitoring

Primary Treatment
Carb-quality focused (at least 175 g/day8, from whole foods and spread across meals and snacks), protein-anchored (80 to 100 g/day) + 10 to 15 minute walks after every meal + sleep optimization
Duration
From diagnosis through delivery; lifestyle continues postpartum to prevent type 2 diabetes
Effect on Underlying Disorder
Most reach glucose targets on diet and activity alone2; lifestyle change after the birth lowers the later risk of type 2 diabetes4
Maternal-Fetal Outcome
Probably fewer large babies, though possibly more inductions of labor13

Full Holistic Approach Includes

  • Protein anchor at every meal (eggs, fatty fish, poultry, lentils, Greek yogurt); 25 to 35 g per meal
  • Carbs from whole foods only, no juice/soda/refined flour; smaller portions at breakfast (most insulin-resistant time)
  • Half the plate non-starchy vegetables; healthy fat (olive oil, avocado, nuts) at every meal
  • 10 to 15 minute walks after every meal (an effective post-meal glucose tool)
  • Bedtime snack with protein + slow carb (e.g., Greek yogurt with berries), which may help keep fasting glucose steady
  • 7 to 9 hours sleep; even one short night worsens insulin resistance measurably
  • Stress reduction (breathwork, gentle prenatal yoga); cortisol raises fasting glucose
  • A prenatal vitamin; other supplements (magnesium, inositol, vitamin D, omega-⁠3) only after discussing them with your maternity team, since none treats gestational diabetes
โš ๏ธ Side effects: Mild fatigue in the first 1 to 2 weeks as eating patterns change. Hypoglycemia rare without medication. Important: If glucose stays above target after 1 to 2 weeks of careful diet and walks, medicine is the right next step. Do not delay it11; uncontrolled glucose is more harmful than insulin.
Supplement Protocol

Evidence-Based Supplements for Gestational Diabetes

Nothing below should be started without your maternity team's agreement, and herbal supplements largely lack pregnancy safety data6. Always confirm with your OB or midwife. Items flagged as contraindicated should not be used during pregnancy. No supplement has been shown to treat gestational diabetes, and none replaces diet, activity or prescribed medicine13.

Supplement What it is for Typical range Timing Notes & cautions
High-Quality Prenatal MultivitaminFoundation. Should contain 800 to 1,000 mcg folic acid (the only form of folate shown to prevent neural tube defects, and processed normally with MTHFR variants), 25 to 30 mg iron, 150 mcg iodine, 8 to 12 mg zinc, B vitamins.1 to 2 capsules/day per productWith breakfast or split AM/PMUniversally recommended. Choose third-party tested (NSF, USP).
Myo-Inositol + D-Chiro-Inositol (40:1)Some trial evidence for preventing GDM, summarized as promising but dependent on formulation and dose6; not established as a treatment once GDM is diagnosed. In women who already have it, two small trials found lower fasting glucose but no clear difference in the need for medicine15.2 to 4 g myo + 50 to 100 mg D-chiro/daySplit, half AM and half PMStudied in pregnancy only in small trials, most in Italy, with doses that varied; check with your midwife or doctor before taking it.
Vitamin D3 (with K2)Correcting low vitamin D; not shown to treat gestational diabetes.2,000 to 4,000 IU D3 + 90 to 180 mcg MK-⁠7 K2 per dayWith fat-containing meal, morningConfirm the dose with your obstetric provider; the Endocrine Society advises against routine vitamin D blood tests in pregnancy. ACOG notes that an optimal serum level in pregnancy has not been established, so there is no target level to aim at. 4,000 IU/day is the adult tolerable upper intake level and was well tolerated throughout pregnancy in a randomized trial; anything above that needs monitoring, and in pregnancy that means your obstetric team. If you take a blood thinner, clear any vitamin K supplement with the clinician managing it before you start or stop: vitamin K interferes with some anticoagulant medicines, and changing your intake can destabilize your monitoring results.
Magnesium GlycinateRequired for insulin receptor activation; an effect on glucose in gestational diabetes is unproven; may help with sleep and leg cramps.300 to 400 mg elemental Mg/dayEvening, 30 to 60 min before bedAgree on the dose with your midwife or doctor. Avoid magnesium oxide / citrate at high doses (laxative). The top of this range is above the 350 mg/day upper intake level for supplemental magnesium; above that, diarrhea is common. With kidney disease, take it only on your clinician's advice.
Omega-⁠3 DHA/EPASupports fetal brain development (DHA); not shown to improve blood sugar in gestational diabetes.1 to 2 g combined EPA+DHA/day; at least 200 to 300 mg DHAWith mealsPregnancy-safe. Third-party-tested low-mercury fish oil or algae oil. Avoid cod liver oil at higher doses (vitamin A). In heart trials, fish oil supplements raised the risk of atrial fibrillation, an irregular heartbeat, more so above 1 g a day24, so check this dose with your clinician first.
Folate (Folic Acid)Required for fetal neural tube and methylation; reduces homocysteine. Folic acid is the only form of folate shown to prevent neural tube defects9.800 to 1,000 mcg/day (usually in prenatal)Morning with foodPregnancy-safe and essential. People with MTHFR variants can process folic acid, so it remains a suitable choice9.
Vitamin B12Insulin signaling, energy and methylation; metformin can lower B12, so ask for a B12 check if you take it.500 to 1,000 mcg/day if levels lowMorning, sublingual or with foodPregnancy-safe.
Iron (only if deficient)Corrects a confirmed iron deficiency; high iron stores have been linked to a higher GDM risk25, so supplement only when tests show a deficiency.30 to 60 mg elemental iron/day if ferritin lowEmpty stomach with vitamin C if toleratedPregnancy-safe when indicated. Take 2 hours from calcium. The top of this range sits above the 45 mg/day tolerable upper intake level for adults. That is appropriate only when correcting a confirmed deficiency under clinical supervision, not as general supplementation. Test ferritin first, and retest rather than staying on it indefinitely.
ProbioticsIn women with gestational diabetes, a review of the trials was uncertain whether probiotics change fasting glucose or the need for insulin, and prevention trials showed no clear effect on the risk of developing it16.Not recommended for gestational diabetes (reviews of the trials found no clear benefit)Not applicableCaution: a Cochrane review found a higher risk of preeclampsia with probiotics in pregnancy (high-certainty evidence) and urged caution; check with your midwife or doctor first.
IodineRequired for fetal thyroid and brain development; many prenatals contain only 150 mcg.150 to 250 mcg/day totalMorning with foodPregnancy-safe at recommended doses. Avoid high-dose kelp/iodine drops without thyroid testing.
Calcium (food + supplement to RDA)Pregnancy RDA 1,000 mg; helps BP, bone and possibly insulin signaling. WHO supports 1,500 mg in low-calcium populations.500 to 1,000 mg/day supplement to reach the 1,000 mg RDA (1,500 mg in low-calcium populations)Split, 500 mg twice daily; 2 hours from ironPregnancy-safe.
Berberine โŒNOT pregnancy-safe; crosses placenta and can cause neonatal hyperbilirubinemia. Studied for insulin resistance outside pregnancy; stop at a positive pregnancy test.Do not use during pregnancyDiscontinue at conceptionContraindicated in pregnancy. Resume postpartum if not breastfeeding. Berberine inhibits CYP3A4 and P-glycoprotein, so it can raise blood levels of many prescription medicines, and it lowers blood sugar on its own. Check with your prescriber before starting it, particularly alongside glucose-lowering medication, an anticoagulant, an immunosuppressant or any drug with a narrow safe range. Not for use in pregnancy or breastfeeding.
โš ๏ธ Pregnancy supplement principle: Confirm every supplement with your OB or midwife. Several supplements promoted for diabetes outside pregnancy (berberine, bitter melon, gymnema, high-dose alpha-lipoic acid) are contraindicated or unstudied in pregnancy and must be reserved for postpartum, and even then berberine is not for use while breastfeeding; check any of them with your doctor first if you are breastfeeding. Diet, movement and sleep are the core during pregnancy; inositol, magnesium and vitamin D are discussions to have with your maternity team6.
What to Expect

What to Expect Over Time

Gestational diabetes usually resolves after birth, and controlling blood sugar lowers risks to mother and baby12.

Treatment and supportive care, together
First Weeks

You test blood sugar, usually fasting and 1 hour after meals, and see a dietitian21. Diet and activity come first; if targets are missed for 1 to 2 weeks, medicine is offered (usually insulin in the US; in the UK, a tablet first, adding insulin if needed)11. Starting medicine is standard care, not a failure2.

Months 1 to 3

Blood sugar can rise later in pregnancy, so medicine may be needed even if diet worked at first21. Growth scans follow, and the birth is usually planned for weeks 38 to 40 21, or 39 to 40 in the US if diet-controlled.

Months 3 to 12

Medicines usually stop at birth, and your baby's blood sugar is checked21. Get a diabetes test after birth: 4 to 12 weeks (ACOG), or 6 to 13 weeks (NICE)14.

Long Term

About half later develop type 2 diabetes10, so keep testing: yearly (NICE) or every 1 to 3 years (ACOG)14.

When to Seek Care

Call your midwife or labor and delivery unit immediately, even at night, if your baby is moving less than usual, you cannot feel movements or the pattern changes; do not wait until the next day22. On insulin, if you feel shaky, sweaty or hungry, look paler or cannot concentrate, test and treat low blood sugar right away21. A severe headache, vision problems such as blurring or flashing lights, severe pain just below the ribs, vomiting or sudden swelling of the face, hands or feet means being seen immediately: call labor and delivery now, because these can be signs of preeclampsia26. See a doctor for increased thirst, peeing more or a dry mouth12.

📬

Get new guides in your inbox. Once a month: new condition guides and research updates, including the trials that did not work. Free, no spam, and you can unsubscribe in one click.

Sign up

Next Steps

Diet First, Medicine When Needed

Diet and activity come first, with medicine added when blood sugar targets are not met. Work with your OB, midwife and dietitian, and remember that starting medicine is standard care, not a failure. Have a diabetes test after the birth, then keep testing regularly.

Explore Diabetes โ†’ Explore Polycystic Ovary Syndrome (PCOS) โ†’

References & Evidence Notes

Each numbered entry below is either a source you can follow or a note setting out what the evidence does and does not support. Both are numbered together so the markers in the text line up.

Last reviewed October 20, 2026. Supplement entries are cross-checked against the NIH National Center for Complementary and Integrative Health and the Linus Pauling Institute Micronutrient Information Center.7 Gestational diabetes is usually managed with diet and movement, and roughly 80% of women reach their glucose targets that way. That is genuine, and it is why the nutrition detail matters so much here. But targets exist for a reason, and if yours are not being met after a week or two of consistent effort, that is not a failure of willpower; it means you need insulin or metformin, and delaying raises the risk of a large baby, birth injury and neonatal hypoglycemia. Take the medication if it is offered. Everything here is designed to work alongside your obstetric and diabetes team, never instead of the monitoring they provide.

  1. On diagnosis: screening is usually at 24 to 28 weeks, earlier where risk factors are present, using either a one-step 75 g oral glucose tolerance test or a two-step approach. Diagnostic thresholds differ between organizations, which is why women sometimes receive different answers depending on where they are tested. ↩
  2. On what diet achieves, and where it stops. Medical nutrition therapy with carbohydrate distribution, glycemic quality and post-meal walking achieves glucose targets in the large majority of women, commonly cited around 70 to 85%. When targets are not met, insulin is first-line, with metformin an alternative in some settings. Escalating is standard management, not a failure of the diet. ↩
  3. On why targets matter: sustained maternal hyperglycemia drives fetal hyperinsulinemia and excess growth, raising the risk of macrosomia, shoulder dystocia, birth injury, cesarean delivery and neonatal hypoglycemia. These risks fall with glycemic control, which is the entire reason for the monitoring. ↩
  4. On what comes after the birth. Gestational diabetes is one of the strongest known predictors of later type 2 diabetes, with a substantially raised lifetime risk. Postpartum glucose testing at 4 to 12 weeks (ACOG) or 6 to 13 weeks (NICE) and regular testing thereafter is recommended and frequently missed. Lifestyle intervention after gestational diabetes reduces progression to type 2 diabetes, which is where the long-term value of this page lies. ↩
  5. On breastfeeding: breastfeeding is associated with lower subsequent maternal glucose intolerance and lower type 2 diabetes risk, alongside its other benefits. It is one of the few postpartum measures with evidence in both mother and child. ↩
  6. On supplements in pregnancy: nothing on this page should be added without your maternity team's agreement. Prenatal vitamins, iodine and vitamin D adequacy are standard; herbal supplements largely lack pregnancy safety data and berberine in particular is avoided in pregnancy. Myo-inositol has some trial evidence in gestational diabetes prevention, summarized in an umbrella meta-analysis as promising while depending on formulation and dose, PubMed 41792927, and remains a discussion to have with a clinician rather than a self-started supplement. ↩
  7. National Center for Complementary and Integrative Health (NIH), nccih.nih.gov, and the Linus Pauling Institute Micronutrient Information Center, lpi.oregonstate.edu/mic. ↩
  8. On carbohydrate in pregnancy: the dietary reference intake for all pregnant people is a minimum of 175 g of carbohydrate a day, and restricting below it can raise fat intake, which may lead to fetal overgrowth, American Diabetes Association Standards of Care 2025, PubMed 39651985. ↩
  9. On which form of folate: folic acid is the only form of folate shown to help prevent neural tube defects, and people with MTHFR variants can process it, CDC, MTHFR Gene Variants and Folic Acid. ↩
  10. On how common it is and why it happens: the US Centers for Disease Control and Prevention states that gestational diabetes affects 5% to 9% of US pregnancies each year and happens when the body cannot make enough insulin during pregnancy, as hormones and weight gain make cells use insulin less well, and that some women already have insulin resistance before pregnancy. It lists gestational diabetes in a previous pregnancy, a baby over 9 pounds, being overweight, a family history of type 2 diabetes, PCOS and some backgrounds (African American, Hispanic or Latino, American Indian, Alaska Native, Native Hawaiian or Pacific Islander) as risk factors. It advises against trying to lose weight during pregnancy and states that about half of women with gestational diabetes go on to develop type 2 diabetes, CDC, gestational diabetes. ↩
  11. On first-line treatment: NICE guidance advises referring everyone with gestational diabetes to a dietitian and, when fasting glucose at diagnosis is below 126 mg/dL (7 mmol/L), a trial of diet and exercise changes first; if blood glucose targets are not met within 1 to 2 weeks, it advises an oral glucose-lowering medicine, and insulin as well if targets are still not met, NICE NG3. ↩
  12. On risks, symptoms and follow-up: NHS guidance states that gestational diabetes usually disappears after the birth and that its risks, including a larger baby, too much amniotic fluid, premature birth, preeclampsia and low blood sugar in the baby, can be reduced if it is found early and well managed. It rarely causes symptoms, but high blood sugar can bring thirst, peeing more, a dry mouth, tiredness, blurred eyesight and vaginal yeast infections. Risk factors include being over 40, a BMI above 30, a previous baby of 10 lb (4.5 kg) or more, gestational diabetes before, a parent or sibling with diabetes, South Asian, Black, African-Caribbean or Middle Eastern origin and weight-loss surgery, and anyone with one of them should be offered screening, NHS, gestational diabetes. ↩
  13. On what treats gestational diabetes: a 2018 overview of Cochrane reviews covering 128 trials found only one effective intervention for treating it, lifestyle change (at a minimum healthy eating, physical activity and self-monitoring of blood sugar) against usual care, which probably means fewer large babies (risk ratio 0.60) but may mean more inductions of labor; no supplement was found effective, PubMed 30103263. ↩
  14. On testing after the birth: NICE guidance advises lifestyle advice and a fasting plasma glucose test 6 to 13 weeks after the birth, or an HbA1c test after 13 weeks if the fasting test has not been done, not routinely a glucose tolerance test, and a yearly HbA1c test if the result is normal, NICE NG3; the American College of Obstetricians and Gynecologists advises a blood test 4 to 12 weeks after the birth and, if it is normal, testing every 1 to 3 years, noting that one third of women who had gestational diabetes have diabetes or milder raised blood sugar soon after giving birth, ACOG, gestational diabetes. ↩
  15. On myo-inositol: a 2023 Cochrane review of seven trials (1,319 women, six of the trials in Italy) found that myo-inositol taken in pregnancy may reduce the chance of developing gestational diabetes (risk ratio 0.53), with low to very low certainty and inconsistent doses and timing, PubMed 36790138; a 2016 Cochrane review of its use as treatment found two small trials (142 women) with lower fasting glucose at the end of treatment but no evidence of a difference in the need for additional medicine, PubMed 27602537. ↩
  16. On probiotics: a 2021 Cochrane review of six prevention trials (1,440 women) could not show whether probiotics change the risk of gestational diabetes (risk ratio 0.80, 95% CI 0.54 to 1.20) and found a higher risk of preeclampsia with probiotics (risk ratio 1.85, high-certainty evidence), and its authors urged caution in using probiotics in pregnancy, PubMed 33870484; a 2020 Cochrane review of nine trials (695 women with gestational diabetes) was uncertain whether probiotics change fasting glucose or the need for insulin, PubMed 32575163. ↩
  17. On diet, activity and medicine in the US: the American College of Obstetricians and Gynecologists states that for many women a healthy diet and regular exercise control blood sugar, that some need medicine even with diet changes and exercise, and that insulin is the recommended medicine in pregnancy; it advises at least 150 minutes of moderate exercise a week and suggests adding a 10 to 15 minute walk after each meal, ACOG, gestational diabetes. ↩
  18. On how many manage with lifestyle alone: the American Diabetes Association's 2025 Standards of Care state that treatment of GDM starts with medical nutrition therapy, physical activity and weight management, and that, depending on the population, 70 to 85% of people diagnosed under Carpenter-Coustan criteria can manage it with lifestyle change alone, with the proportion expected to be higher under lower diagnostic thresholds, American Diabetes Association, Standards of Care 2025, section 15. ↩
  19. On preventing type 2 diabetes afterward: in the Diabetes Prevention Program, among 350 women with a history of GDM and impaired glucose tolerance, both an intensive lifestyle program and a glucose-lowering tablet reduced the incidence of diabetes by about 50% against placebo, PubMed 18826999. ↩
  20. On recurrence: a 2025 meta-analysis of 31 population-based studies found that GDM recurred in 51% of later pregnancies, with higher risk after insulin treatment in the first pregnancy, weight gain between pregnancies, overweight or obesity and a family history of diabetes, PubMed 40929983. ↩
  21. On treatment and the birth: NHS guidance advises testing blood sugar before breakfast and 1 hour after meals, referral to a dietitian, and medicine if blood sugar is not stable 1 to 2 weeks after changing diet and exercise, noting that it can rise as pregnancy goes on so medicine may be needed later. Insulin can cause low blood sugar, felt as shakiness, sweating, hunger, paleness or poor concentration, which should be tested and treated right away. Growth scans are offered at 28, 32 and 36 weeks, the birth is usually around weeks 38 to 40, the baby's blood sugar is checked after birth, and blood sugar medicines usually stop after the birth, NHS, gestational diabetes treatment. ↩
  22. On baby movements: NHS guidance advises calling your midwife or labor and delivery unit immediately, even in the middle of the night and without waiting until the next day, if your baby is moving less than usual, you cannot feel your baby moving or the usual pattern of movements changes, and advises against using a home heartbeat monitor to check, NHS, your baby's movements. ↩
  23. On carbohydrate at each meal: the American Diabetes Association's sample meal plan for gestational diabetes gives 2 servings of carbohydrate at breakfast and 4 at lunch and at dinner, with snacks, as a guide to work out with a dietitian for each person's needs, American Diabetes Association, sample meal plan for gestational diabetes (2025); the CDC counts one carb serving as about 15 g of carbohydrate, CDC, carb counting. ↩
  24. Gencer B, Djousse L, Al-Ramady OT, Cook NR, Manson JE, Albert CM. Effect of long-term marine omega-⁠3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes: a systematic review and meta-analysis. Circulation. 2021;144(25):1981-⁠1990. PubMed 34612056. Seven trials with 81,210 people followed for about 5 years: omega-⁠3 supplements were linked to a higher risk of atrial fibrillation (hazard ratio 1.25), more so in trials of more than 1 g a day (1.49), and the risk rose with each additional gram. ↩
  25. On iron and gestational diabetes: a 2025 meta-analysis of observational studies, including 30 studies of serum ferritin, found that women with the highest ferritin levels had a higher risk of gestational diabetes than those with the lowest, and concluded that high ferritin and high iron levels are associated with an increased risk, PubMed 40313887. ↩
  26. On warning signs of preeclampsia: the NICE guideline on hypertension in pregnancy advises pregnant women to see a healthcare professional immediately for a severe headache, vision problems such as blurring or flashing before the eyes, severe pain just below the ribs, vomiting or sudden swelling of the face, hands or feet, NICE NG133. ↩