Gestational Diabetes

Contents

1. The pancreas and the placenta pull against each other
2. Some women start pregnancy closer to the threshold
3. Screening usually falls between 24 and 28 weeks
4. Extra glucose reaches the fetus
5. Management rests on measurement, food and movement
6. The risk outlasts the pregnancy
7. Research is moving the clock earlier

Gestational diabetes is among the conditions met in the pregnancies, high risk and routine alike, that Candace Cooley has managed, and its account begins with two organs. One is the pancreas, whose beta cells release insulin, the hormone that moves glucose out of the blood and into the cells that burn it. The other is the placenta, the temporary organ that feeds the fetus and, along the way, floods the mother’s circulation with hormones. Gestational diabetes is what happens when the second organ asks more of the first than it can deliver.

The pancreas and the placenta pull against each other

MedlinePlus Genetics, from the National Library of Medicine, describes a reduced response to insulin as a normal part of pregnancy, one that keeps enough glucose available for the growing fetus. To hold blood glucose steady against that resistance, the beta cells step up their output, and in most pregnancies they keep pace. In some women they cannot, and the result is raised blood glucose, called hyperglycemia, the defining feature of the condition.⁶ The American College of Obstetricians and Gynecologists puts the same mechanism simply: rising pregnancy hormones interfere with insulin, and when the body cannot make enough extra insulin, sugar levels go up.¹ A 2013 CNN explainer adds that the placenta makes more of these hormones as it grows, so the resistance deepens across pregnancy.⁸

Figure

How glucose control strains in pregnancy

1. 01
   MealBlood glucose rises after eating.
2. 02
   ReleaseBeta cells in the pancreas release insulin, which moves glucose from the blood into cells.
3. 03
   ResistanceAs a normal part of pregnancy the body responds less to insulin, keeping glucose available for the fetus.
4. 04
   CompensationBeta cells make more insulin, and in most pregnancies this keeps glucose in the normal range.
5. 05
   ShortfallWhen the beta cells cannot raise output enough, blood glucose climbs and gestational diabetes results.

Some women start pregnancy closer to the threshold

The Centers for Disease Control and Prevention notes that every woman has some insulin resistance late in pregnancy, but that some begin pregnancy with resistance already present and so need more insulin from the start.⁷ Its list of risk factors includes gestational diabetes in an earlier pregnancy, a previous baby over 9 pounds, overweight, a family history of type 2 diabetes and polycystic ovary syndrome.⁷ MedlinePlus Genetics adds age over 35 and prediabetes, and says common variations in several genes, many shared with type 2 diabetes, act together with health and lifestyle factors.⁶ Risk also varies by ancestry, with higher rates among Native American, Asian, Hispanic and African American women.⁶ ACOG stresses that the condition can also appear in women with none of these factors, and notes that some women diagnosed in pregnancy probably had mild diabetes beforehand without knowing it; for them, the diabetes does not resolve after birth.¹

Screening usually falls between 24 and 28 weeks

Because most affected women feel nothing, the condition is usually found through routine testing rather than symptoms; the CDC says any symptoms tend to be mild, such as extra thirst or more frequent urination.⁷ ACOG advises that every pregnant woman be screened: those with risk factors are tested early, and the rest between 24 and 28 weeks.¹ The CDC notes that a high reading early in pregnancy may instead point to type 1 or type 2 diabetes that was present before conception.⁷ The CNN explainer describes the common screening test, in which a measured glucose beverage is taken and blood is drawn from the arm about half an hour later to see how the body clears it.⁸ Where this test sits among the other timed checks of pregnancy is laid out in the prenatal care schedule.

Figure

Usual testing window and the case for moving it

	Usual practice	Proposed by a 2024 review series
When glucose is tested	Between 24 and 28 weeks	Before 14 weeks
Where it applies	England and many other countries	Called for by 28 academics from 13 countries
Evidence cited	The current standard	High glucose in the first 20 weeks carried worse outcomes, and earlier treatment reduced those risks

Extra glucose reaches the fetus

When a mother’s blood sugar runs high, her body passes more sugar to the fetus than it needs, and the fetus can gain a lot of weight. ACOG lists the consequences of a baby of 9 pounds or more: harder labor, cesarean birth, heavy bleeding after delivery and serious tears during a vaginal birth.¹ A 2024 ACOG article notes that such babies tend to carry extra fat in the shoulders and abdomen, raising the chance of shoulder dystocia, and that after birth they may have low blood sugar, jaundice or trouble breathing.² ACOG also links the condition with high blood pressure and with preeclampsia, both more common in women who have it.¹ MedlinePlus Genetics adds that, left untreated, it raises the risk of early delivery.⁶

Management rests on measurement, food and movement

Treatment aims to hold glucose inside a target range until delivery. Women check their levels several times a day with a glucose meter and keep a log for each visit, and prenatal visits become more frequent.¹ ACOG notes that most women manage with eating and activity alone, often guided by a nutritionist; when that is not enough, insulin is the preferred medicine, because it does not cross the placenta, and an oral medicine is sometimes used instead.² ACOG adds that tests of fetal wellbeing, such as kick counts, the nonstress test and the biophysical profile, may be added in the later weeks of pregnancy, and that most women whose glucose is controlled carry to full term.¹ The same article is direct about cause: nothing a woman ate gave her the condition, and the placental hormones, not her diet, are what drive it.² How eating and weight gain fit the wider picture is covered in nutrition and weight gain in pregnancy.

The risk outlasts the pregnancy

Once the placenta is delivered, the hormones that drove the resistance fall away, and in most women blood sugar returns to normal.² The longer view is less reassuring. MedlinePlus Genetics reports a 30 to 70 percent chance of recurrence in a later pregnancy, and says about half of affected women develop type 2 diabetes within a few years.⁶ ACOG recommends a glucose test 4 to 12 weeks after birth and, if that is normal, repeat testing every 1 to 3 years.¹ Children born after these pregnancies carry a higher risk of obesity and diabetes, which the NICHD’s Epidemiology Branch describes as a cycle across generations that its research aims to interrupt.³

Figure

Gestational diabetes in figures

of US pregnancies affected

Up to 14%

chance of recurrence in a later pregnancy

30 to 70%

develop type 2 diabetes within a few years

About half

Research is moving the clock earlier

The usual testing window may come too late. A 2020 NICHD study of more than 2,400 pregnancies found that fetuses of women with the condition were measurably heavier by 28 weeks, and that higher maternal glucose as early as weeks 10 to 14 tracked with larger fetal size by week 20.⁴ In an interview with NIH MedlinePlus Magazine, the study’s lead investigator described work toward predicting the condition around week 10 rather than week 28, and reported that women who avoided smoking, exercised, ate well and kept a healthy weight before pregnancy had a far lower risk.⁵ In 2024 The Guardian reported on a review series by 28 academics from 13 countries calling for testing and treatment before 14 weeks. The paper called the condition the most common medical complication of pregnancy, affecting one in seven pregnancies worldwide, and the authors found that women with high glucose in the first 20 weeks fared worse than those whose condition appeared later, and that earlier treatment reduced those risks.⁹ The NICHD branch, for its part, continues to study diet, lifestyle and genetic risk factors with the aim of preventing the condition before it starts.³

Even well run screening has limits worth naming. A test at 24 to 28 weeks cannot detect glucose that rose months earlier, and by the time it is done, fetal growth may already have begun to diverge, as the NICHD study found. Good control during pregnancy lowers the immediate risks but does not erase the higher lifetime chance of type 2 diabetes, which is why testing continues for years after birth. And a diagnosis says nothing about a woman’s character or her meals. How any one woman is tested and treated is a plan to settle with her own clinician.