Blood Sugar Levels During Pregnancy

Blood sugar levels can vary during pregnancy
Blood sugar levels can vary during pregnancy

Blood glucose control is one of the most important factors during pregnancy. Tight blood glucose control, helps to ensure the best chance of a successful pregnancy.

Diabetes control is important for people who have diabetes going into their pregnancy as well as people who develop diabetes during their pregnancy (gestational diabetes).

What is gestational diabetes?

It has been reported that on average 2% to 4% of women develop temporary diabetes also known as gestational diabetes.

This happens because they are unable to produce an increased amount of insulin to overcome the resistance levels.

In gestational diabetes there is not normally any show of external symptoms normally recognised as characteristic of the disease for example excessive thirst, tiredness and increased urination.

Blood sugar control during pregnancy

Good blood glucose control reduces the risks of complications developing for the mother and baby.

The target HbA1c for mothers before and during pregnancy is 6.1% (or 43 mmol/mol). [91]

People with diabetes before their pregnancy will be advised to keep excellent control of their blood sugar before and throughout the pregnancy.

The first eight weeks of the pregnancy are a critical period and so it is highly recommended that strong control is achieved prior to becoming pregnant wherever possible.

Mothers who develop gestational diabetes will be treated initially with diet and exercise but may be put onto oral hypoglycaemics (tablets) or insulin injections if blood sugar levels remain high.

Diabetes management

To help you to meet the challenging blood glucose targets, you will be expected to test your blood glucose before each meal and 1 hour after eating.

People taking insulin for their diabetes will also need to test before bed each night.

You will have blood tests performed at various intervals during your pregnancy to check your diabetes is under good control.


Diabetes can be present before pregnancy or may develop during pregnancy itself. If you develop diabetes during pregnancy, in most cases this will be a specific type of diabetes known as gestational diabetes.

Blood sugar levels are important for all mothers to be with diabetes –as well controlled blood glucose levels can significantly increase the likelihood of having a healthy baby. The NHS advises the target HbA1c for mothers before and during pregnancy is 43 mmol/mol (or 6.1%).

If you have diabetes prior to your pregnancy, the NHS advises achieving the target HbA1c before conceiving.

The target HbA1c target may require dedication to reach, but its important that you strive to achieve it. You might find that, Regular blood glucose testing, including before each meal and 1 hour after will help you to keep your blood glucose levels under control.

If blood glucose levels are higher than recommended, you may need to change your medication regime to help lower your sugar levels Your health team will provide you with advice for managing your blood glucose levels throughout your pregnancy.

Sometimes, The emphasis on achieving tight blood glucose control may bring on hypoglycemia, particularly amongst those using insulin. Your health team should ensure you know how best to spot and treat hypoglycemia.

You should expect to receive a high standard of care from your health team throughout your pregnancy and should have the opportunity to ask any questions you may have about achieving your health targets.

How does diabetes affect the baby?

There have been reports that diabetes during pregnancy brings increased chances of having a bigger babies and birth defects.

Infant mortality and birth defects

There is a slight increase in the risk of infant mortality or birth defects in baby’s of mother with diabetes than without, however preconception care can reduce this risk by ensuring the mother is as healthy as possible before and through out pregnancy.

In addition to this if a woman has diabetes before pregnancy, diabetes related complications can worsen; this includes things like hypertension, kidney disease, nerve damage and retinopathy which is a form of diabetic eye disease.

Excess insulin

The baby of a woman with diabetes often produces excess insulin in response to high blood glucose levels within the body of the mother.

In type 1 diabetes no significant extra insulin will be produced by your body so you may see your insulin requirements increased. Your health team should be able to advise with the best way to manage your diabetes.

At birth the baby's blood glucose levels may be hypoglycemic; the blood glucose level is reduced as a result of the removal of the maternal glucose source.

This is detected by a heel stick blood test and can be restored to a normal level with either oral or intravenous glucose. In addition to this a further glucose tolerance test should be done at the six-week postnatal check in order to establish whether any further treatment needs to be considered.

Foetal Macrosomia

When a pregnant woman has an abnormally high level of blood glucose, the baby will naturally store excess glucose as body fat. For this reason, the baby will be larger than average upon reaching the gestation date.

This is a condition known as foetal macrosomia.

If a woman has gestational diabetes, there have been reports that 50% of these women will go on to develop type 2 diabetes within 10 to 15 years.

Risk factors for developing diabetes during pregnancy

There is an increased risk of diabetes during pregnancy if:

  • The woman is overweight
  • The woman is a smoker or around smokers more than average
  • The woman is older (over 30)
  • There is a family history of diabetes
  • The woman is from an ethnic minority
  • There is previous history of the birth of a large baby (more than 4.5 kg or 10lbs)

There is a routine antenatal test used to measure glucose levels in urine; however it has been noted it is relatively unreliable for diagnosing diabetes.

Therefore blood sugar levels are checked between 26 and 30 weeks of gestation. This is done of two separate occasions using one of two tests, either the fasting glucose test or the random glucose test. In addition to this if there are any abnormal results of these tests or there is a family history of diabetes, or a woman is regarded as obese she will be offered a glucose tolerance test.

Often with gestational diabetes, the woman is advised to take a number of steps to change their diet and exercise habits to ensure the best possible pregnancy.

It is reportedly advisable to increase participation in low-impact activities such as walking, swimming, yoga and pilates. In addition to this it is advisable to eat regular meals watching the amount of fat being eaten, remembering it is controlling the amount of fat not cutting it out of the diet completely.

Also reducing the amount of salt in the diet and ensuring that plenty of fruit and vegetables are included in the diet.