Why does diabetes in pregnancy occur and does it matter?

As a baby grows in the womb, a mother’s body releases many different hormones, proteins and other chemical signals… it’s a crazy time! But it’s important to understand how lifestyle choices, such as diet, can influence both the mother’s and baby’s health.

As pregnancy progresses to the end second trimester and into the third, the mother’s body continues to change, her stomach and breasts increases in size, her hips widen as the baby continues to grow and develop.

What is impaired glucose tolerance?

Apart from the obvious, there are further unseen changes that occur in her body. The placenta, an organ that acts as the unborn child’s food source, releases signals known to influence the type of fuel (food) reaching the baby. Placental hormones, along with others released by the mother’s fat cells, cause the mother to become somewhat insulin resistant in the stages of pregnancy. This basically means the mother’s muscle cells do not respond to the insulin she has released, and consequently, she has difficulty using sugar from her blood. This is known as impaired glucose tolerance.

Why do women become insulin resistant in pregnancy?

But hang on, isn’t insulin resistance and impaired glucose tolerance related to diabetes? Why does a perfectly healthy pregnant women have insulin resistance?

…Because our bodies are clever and have learned to adapt!

Insulin resistance is actually an ancient survival mechanism. Our bodies have evolved to enable the mother to protect herself and her unborn baby during periods of fasting, when food was not plentiful. Insulin resistance allows the mother to use her fat stores as a source of fuel, by blocking her muscle cells from absorbing sugar, and spares the carbohydrate (sugar) for the rapidly growing unborn baby.

Unfortunately, in our modern world, there is usually too much food around. Mother’s tend to have plenty of fat stored in their cells, and are able to access adequate, or often, too much food during pregnancy. Excess fat, particularly around the stomach, combined with genetics puts the expectant mother at a greater risk of troublesome insulin resistance. Adding to this, women are generally waiting until later in life before becoming pregnant, which can amplify the effect of pregnancy insulin resistance. Insulin resistance in this instance can cause blood glucose levels to rise above normal, known as gestational diabetes (pregnancy diabetes).

The medical and scientific community are well aware that increased body fat, genetics and age are the biggest risk factors for gestational diabetes (A Prospective Study of Pregravid Determinants of Gestational Diabetes Mellitus). So, ensuring that the mother is in good health before pregnancy and is receiving nutrition and health advice from a qualified health care team is paramount to reducing the risk of developing gestational diabetes.

How common is gestational diabetes?

The number of women living with diabetes is increasing. The prevalence of gestational diabetes is related to the prevalence of type 2 diabetes (The Increasing Prevalence of Diabetes in Pregnancy). This means, that as the number of people with type 2 diabetes increases, so does the number of cases of gestational diabetes.

The International Diabetes Federation estimated that in 2017:

  • 204 million women aged 20-79 years, have diabetes. This number is set to increase to 308 million by 2045
  • 1 in 3 women of reproductive age lives with diabetes
  • 21.3 million (16.2%) of live births had some form of hyperglycaemia in pregnancy. It was estimated that 85.1% were due to gestational diabetes
  • 1 in 7 births were affected by gestational diabetes
  • Hyperglycaemia in pregnancy is mostly prominent in low- and middle-income countries where maternal care is limited

What are the risk factors for developing gestational diabetes?

Every pregnant woman is at risk of developing gestational diabetes, so it is recommended that all pregnant women are screened using a glucose tolerance blood test at 24-28 weeks’ gestation.

There are some women who are at a much higher risk and should be screened before becoming pregnant, at 12 weeks’ gestation and again at 24-28 weeks if not previously diagnosed.

There are a number of risk factors that increase your likelihood of developing gestational diabetes. Like with type 2 diabetes, extra weight is linked to gestational diabetes. This means that women who are overweight or obese, may already have insulin resistance before they become pregnant. Gaining too much weight during pregnancy can also increase the risk of developing gestational diabetes.

Other high-risk factors for developing gestational diabetes include:

  1. women aged 25 years or over
  2. family history of type 2 diabetes
  3. family history of gestational diabetes, especially from a first-degree relative like a mother or sister
  4. being overweight or obese
  5. had gestational diabetes in a previous pregnancy
  6. multiple pregnancies in the past
  7. have previously given birth to a large baby (weighing more than 4.5kgs)
  8. gained weight rapidly during the first trimester of pregnancy
  9. a previous diagnosis of Polycystic Ovary Syndrome
  10. of non-Caucasian descent, including African-American, Aboriginal or Torres Strait Islander, Melanesian, Polynesian, Chinese, Southeast Asian, Middle Easter or Indian background

To the point:

  • Insulin resistance happens to some extent, in all pregnancies. It’s a survival mechanism to help the unborn baby to continue to grow in times where there are limited food sources.

  • Increased fat (particularly around the tummy) causes an increase in insulin resistance in pregnancy, this is further amplified by age and genetics.

  • Insulin resistance can cause increase blood glucose levels above normal values known as gestational diabetes.

Please see the following articles for more information:

What should I do next?

If you experience any symptoms of gestational diabetes or you have risk factors for developing gestational diabetes, it is important to be tested at 24-28 weeks gestation. Some people are at higher risk than others. If you are 25 years or older or have other risk factors for diabetes, you may require testing earlier in pregnancy. By diagnosing and treating gestational diabetes, it means you can decrease the risk of developing or delay any further health complications of gestational diabetes. These complications can affect both you and your child later in life, for example you are both at risk of developing type 2 diabetes. It is important to know that diagnosing diabetes should not rely solely on using a Hb A1c test.

Once you learn what your gestational diabetes status is, or if you already have gestational diabetes, the next most important step is to become educated. You can join the Gestational Diabetes Program to help you learn how to manage gestational diabetes and improve health outcomes for you and your child. The program is personalised and tailored, giving you more of the content that you want. The program also helps you to stay motivated and teaches you what changes you need to make.