It is generally thought that about one third of people with diabetes don't know they have it. This is mostly true of type 2 diabetes, as type 1, which is the inability to produce insulin at all, generally occurs and is diagnosed early in life.
In the UK, a mother-to-be who is unaware that she has diabetes will in all likelihood find out if she has the disease in the very early stage of her pregnancy, as their doctor will take a urine sample and check for the disease.
However, as well as type 1 and type 2 diabetes, there is also a diabetic condition called gestational diabetes. This affects some women who are not diabetic in any form before pregnancy, but become so in and during the latter stages of their pregnancy.
In this case, the mother-to-be will have to monitor her blood glucose closely, and keep it stable by injecting insulin, which is something that can be a little stressful for some, rather than take any oral medication. This is because oral medications used for treating diabetes can damage the foetus.
Type 1 sufferers must pay close attention to diet and blood sugar in the run up to conception, and may find that they need more insulin than normal when pregnant. This is because a side effect of pregnancy is a hormone that makes the insulin less effective than when the woman is not pregnant.
Type 2 diabetics also need to monitor their sugar levels closely during pregnancy, and will also, if they are using any oral medication, learn how to inject insulin for the same reason as those who contract gestational diabetes.
In all cases, these people should be closely checked by their medical teams.
The reason why blood sugar levels need to be monitored and kept stable is because if not, there is an elevated risk of a miscarriage or a congenital deformity.
Combine these risks with the fact that smoking can also contribute to damaging your newborn, and you have the perfect motivation for quitting smoking, taking some exercise (moderate gentle exercise during pregnancy is a good idea) and embarking on a new diet, to get both the baby and the mother in good shape.