Why do some women get diabetes when they are pregnant? Is this dangerous for them or their baby?

Why do some women get diabetes when they are pregnant? Is this dangerous for them or their baby?

Pregnancy is a situation in which insulin resistance (see Question 2) is a normal feature. This is because it is beneficial for the nutrients absorbed from a pregnant woman’s meals to be channeled first to the growing fetus. The development of maternal insulin resistance in the second half of pregnancy assures that this will occur. At least part of the reason for the development of maternal insulin resistance is that the placenta produces substances that lead to insulin resistance and as the placenta grows, the insulin resistance increases.

This is called physiologic (i.e., normal) insulin resistance. Indeed, a healthy pregnant woman may be more insulin resistant than the average patient with type 2 diabetes! However, the vast majority (>95%) of otherwise healthy pregnant women do not get diabetes in this situation because the pancreas is able to make enough insulin to overcome the insulin resistance and keep the glucose levels normal. A small minority of women cannot do so and their glucose levels rise.

These women tend to be the same women who are destined to get type 2 diabetes later in life. The risk of developing type 2 diabetes is much higher in a woman who has had diabetes detected in pregnancy ( gestational diabetes mellitus or GDM). GDM provides a unique opportunity to follow the natural history of type 2 diabetes in the years prior to its onset in women, since most GDM goes away very rapidly, often within hours, after the baby is delivered and reappears in later life as type 2 diabetes.

If untreated, GDM can cause harm to both mother and baby, especially at or soon after delivery. Fortunately, outcomes of GDM are generally excellent in most developed countries.

A healthy pregnant woman may be more insulin resistant than the average patient with type 2 diabetes!

Gestational diabetes mellitus (GDM)
Diabetes detected in pregnancy.