Toggle site contrast Toggle Contract

Antenatal screening for diabetes in pregnancy

Read our guide below about antenatal screening for diabetes in pregnancy.

You can also download a PDF version of this patient information by following the link on the right.

What is gestational diabetes?

It’s a form of diabetes which affects an estimated 5% (5 in 100) of pregnant women. There’s no known specific cause but it’s believed the pregnancy hormones may block the insulin action in the pancreas resulting in high blood sugars.

High blood sugar levels in the mother’s body pass through the placenta to the developing baby. The increased levels can result in an increased rate of complications including:

  • large size at birth
  • birth trauma
  • hypoglycemia (low blood sugar) for the baby
  • jaundice.

What you can do to reduce risk

Maintaining control of blood sugar levels significantly reduces the risk to the baby. If we discover this type of diabetes, our doctors and midwives will explain how to monitor your blood glucose levels and monitor the growth of your baby.

When does gestational diabetes occur?

Gestational diabetes usually begins in the second half of pregnancy and goes away after the birth.
Occasionally, we discover gestational diabetes in the first months of pregnancy which could suggest diabetes existed before you
were pregnant.

Booking visit

When you first see your midwife for the booking visit, we’ll take various blood tests. One of these is to test for diabetes in pregnancy with a random blood glucose (sugar test).

A normal result is below 7.0mmols.

If your test is normal, you won’t need any further tests. If the result is above normal, you’ll need a further test called a glucose tolerance test (GTT). We’ll send you a letter explaining this.

Who is at increased risk from gestational diabetes?

We ask women considered to be at a slightly increased risk of having gestational diabetes to have a GTT. We’ll discuss this with you at your first booking appointment.

You may be at increased risk if:

  • you have had a previous baby weighing over 4.5kgs
  • there’s a family history of diabetes or gestational diabetes (parent or sibling only)
  • your family origin is South Asia, black Caribbean or Middle Eastern
  • your Body Mass Index (BMI) is over 30 (a ratio of your weight and height calculated by your midwife)
  • you suffer from polycystic ovarian syndrome
  • you have had a stillbirth or unexplained pregnancy loss after 28 weeks of pregnancy.

You might also be at increased risk of you have any specific factors arising during pregnancy. For example:

  • glucose++ in your urine on 1 occasion,
  • glucose+ on 2 occasions
  • an increase of fluid around the baby (polyhydramnios).

What is a GTT?

A GTT is a test where your body is challenged with a measured dose of sugar.

You must not eat or drink for 12 hours before the test. Sips of water are allowed.

No smoking before the test. Talk to your midwife if you need help to stop smoking.

What happens during a GTT ?

We’ll take an initial blood test and ask you to have a glucose drink. We’ll then ask you to stay in the hospital clinic for the next 2 hours to sit and rest. Please bring a book or magazine to read.

2 hours after the glucose drink we’ll take another blood test. After we take the second blood test, you can leave and carry on as normal.

We’ll contact you if the result is positive and refer you to our diabetes specialist midwife.

You may wish to bring a healthy snack to eat following your GTT test.

How do I arrange a GTT?

Your community midwife, GP or hospital doctor will arrange a GTT for you.

These tests are in high demand. If you can not attend please call us on the number below, depending on which hospital you’re attending for your test, to rearrange.

GTT results

If your results are above the expected normal levels for pregnancy we would treat you as having gestational diabetes.

We’ll refer you to a diabetes specialist midwife for care and advice. We’ll also see you in the antenatal clinic.

Reducing associated healthcare infections

Find out how you can help to reduce healthcare associated infections when visiting hospital

About our patient information pages and leaflets

This patient advice is intended as general information only. We aim to make the information as up to date and accurate as possible, but please note that it is subject to change.

Always check specific advice on any concerns you may have with your doctor.

Stoke Mandeville Hospital Antenatal Clinic
Wycombe Hospital
Amersham Hospital
Diabetes Specialist Midwife
Stoke Mandeville Hospital Antenatal Clinic

01296 316227

Wycombe Hospital

01494 425234

Amersham Hospital

01494 734244

Diabetes Specialist Midwife

07798 581108