Screening for Diabetes in Pregnancy

The Oral Glucose Tolerance Test

During the antenatal booking appointment which is ideally done between 8 and 12 weeks, a whole list of questions are asked. This in itself is a screening tool. The midwife is assessing your health and the potential risks to you and your baby throughout your pregnancy and postnatally.

One set of questions will assess your need for the Oral Glucose Tolerance Test (OGTT). If you have any of the following you will be offered the OGTT.

  • BMI above 30 kg/m2
  • previous macrosomic baby weighing 4.5 kg or above
  • previous gestational diabetes
  • family history of diabetes (first‑degree relative with diabetes)
  • minority ethnic family origin with a high prevalence of diabetes.

An OGTT is usually performed optimally at 28 weeks and done in 2 parts. You will be required to fast 8-12 hrs prior to the test. Avoiding all food and drink other than plain water. Some medications may have to be omitted but not all – please check with your midwife/obstetrician prior to the test.

You will then have your fasting blood test. Immediately after you will have a measured glucose drink. 2 hours later you will have a second blood test. After this second blood test you will then be able to eat and drink as normal.

Results are usually available the same day or the following day. Most trusts work on the basis that you will only be contacted if the result is abnormal.


Diabetes in pregnancy if left undetected can lead to serious complications for you and your baby. These include a large baby, pre eclampsia, polyhydramnios, premature labour and very low blood sugars for baby when born. If diabetes is detected and blood sugar levels are well controlled then pregnancy can be completely normal albeit with extra monitoring such as growth scans.


That depends on your sugar control. Most women with any form of diabetes will be advised to have an induction of labour (or cs if appropriate). The RCOG guidelines advise induction between 37 and 39 weeks for type 1 and type 2 and before 40+6 for GD. Your blood sugars will need to be monitored at regular intervals throughout the labour. If you require medication orally or insulin then your birth options will probably be more limited. You will need monitoring and potentially need a drip. However your midwife will try their best to keep as many options open to you as possible. It really is case dependant and your specialist team will be able to discuss this with you.

Following the birth you will be advised against early discharge before 24 hours. Your baby will also need blood glucose monitoring. Your baby may have trouble maintaining a good blood glucose level due to maternal diabetes.


Most women will have a normal result from a postnatal OGTT.


For more information check out these websites

NICE Guidelines Diabetes in pregnancy: management from preconception to the postnatal period

Diabetes UK 0345 123 2399

NHS Choices Gestational Diabetes




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