Gestational Diabetes: What the Glucose Test Actually Means

Between 24 and 28 weeks, most women are handed a sugary drink and asked to sit still for an hour. The test is unpopular and frequently misunderstood, so it is worth knowing what the number on the result actually represents.

Screening and diagnosis are different steps

The one-hour test is a screen, deliberately set low so it catches people who need a closer look. Roughly a quarter of women who fail it turn out to have normal glucose tolerance on the longer three-hour test. Gestational diabetes is diagnosed when two or more values on that longer test are above the threshold, which is why a single high reading is not the same thing as a diagnosis.

What the diagnosis changes

Placental hormones make insulin less effective, which is why glucose tolerance shifts in the second half of pregnancy and usually returns to normal after birth. Management is mostly unglamorous: eating regularly with protein and fat alongside carbohydrates, walking after meals, checking blood sugar at home, and, for perhaps a third of women, medication. The payoff is real. Keeping glucose in range lowers the chances of a very large baby, a difficult delivery and newborn blood sugar problems.

• Walk for 10 to 15 minutes after meals; muscles take up glucose without extra insulin.
• Pair carbohydrates with protein or fat rather than eating them alone.
• Test as advised rather than more often; more strips rarely mean more information.
• Expect a repeat glucose test about six weeks after birth, then every few years.

The part that gets lost

Gestational diabetes is a condition of the placenta, not evidence that you ate badly or failed at pregnancy. It appears in athletes and in people with impeccable diets. The single most useful thing you can do is eat and test consistently for the weeks that remain, and then let it go: for most women it ends the moment the placenta does.