Type 1 diabetes in pregnancy 

One of the first things a female with diabetes and her family will ask is whether she will be able to have babies. Being pregnant exerts a certain strain on every woman, but there is no reason to discourage women with diabetes from having children. The mother′s risk of developing diabetes complications later in life is not affected by pregnancy. Of the children born in UK and US, approximately 0.3% have a mother with diabetes. About 70% of these mothers have Type 1 diabetes. Gestational diabetes (a temporary form of diabetes occurring during pregnancy) affects 3-5% of pregnancies. The symptoms of diabetes usually disappear after the birth but these women have an increased risk (40-60%) of acquiring Type 2 diabetes later in life.

If the mother′s blood glucose level is high, there is a risk that the unborn baby will be affected. However, if the woman has good glucose control with an HbA1c similar to that of an individual without diabetes at the time the baby is conceived and during early pregnancy, older studies show that the risk of birth defects or miscarriage is no greater than average. This is the case even if the mother has diabetes complications. The risk increases with increasing HbA1c and is close to 25%! when HbA1c is above 11%. It is therefore very important to plan your pregnancy, if at all possible, and to try to ensure that your HbA1c is below 7% before you get pregnant. More recent data show that this may not be low enough.

A UK study found a major birth defect in 4.2% of children of diabetic mothers compared with 2.1% in the general population. One quarter of the women who had a baby with a birth defect had an HbA1c value of less than 7% by 13 weeks of pregnancy. However, it is important to point out that even if your HbA1c is high during pregnancy, this does not necessarily mean your baby will have something wrong with it.. Fifty per cent of all women with a high HbA1c (above 10%) have quite normal pregnancies.

Most major malformations can be identified by ultrasound or a blood test. The babies of women with Type 2 diabetes have risks of birth defects and problems at birth comparable to those of babies of women with Type 1 diabetes. There is an increased risk of birth defects and difficulties at delivery even with diabetes that is identified during pregnancy (gestational diabetes). However, these risks are associated with diabetes in the mother and do not apply if only the father has diabetes.

Insulin requirements may decrease early in pregnancy, especially if the woman has problems with sickness. Thereafter, the amount of insulin needed rises steadily, until close to full term (36-38 weeks), when it is often as much as twice the level it was before the pregnancy. This increased need for insulin is partly caused by weight gain during pregnancy but also by hormones excreted from the placenta, which counteract the blood glucose-lowering effect of insulin. The average weight gain during pregnancy is around 11-12 kg (24-26 lb) but individuals vary greatly.

Although eye and kidney damage may be accelerated by pregnancy, these changes have been found by the DCCT study to be reversible once the pregnancy is over. However, if the mother′s kidneys have been damaged by her diabetes, the risk of fetal growth retardation and premature birth will increase considerably.

Short periods of hypoglycaemia are not dangerous to the unborn baby. However, severe hypoglycaemia with seizures or unconsciousness can be dangerous. Low blood glucose levels can increase “morning” sickness during pregnancy. Feeling very sick may make it difficult to eat regular meals, resulting in hypoglycaemia. A vicious cycle may easily develop. The use of an insulin pump can be an effective way of minimizing these problems.

Glucose in the mother′s blood will pass easily through the placenta into the blood of the unborn baby. In this way, the baby is continuously consuming a large proportion of the mother′s glucose, leading to a risk of hypoglycaemia when she does not eat regularly. This may result in her needing more snacks during the day and increase the risk of night time hypoglycaemia.

If the mother′s blood glucose level is increased, some of the glucose will be delivered via the placenta to the baby – whose own pancreas can produce enough insulin to take care of the extra sugar. However, insulin cannot pass back to the mother through the placenta. If the blood glucose level is high during a large part of the pregnancy, the baby will grow faster than it should, and will have gained excess weight by the time it is born. This may cause problems at delivery.

Even if the HbA1c during pregnancy is kept well controlled, the child may have gained excess weight by the time it is born. The blood glucose level after meals seems to be most significant according to one study. The recommendation in this study was to aim for a blood glucose level of approximately 7.3 mmol/l (130 mg/dl) 1 hour after the meal. With lower levels there was some risk that the baby would show a slight retardation in growth, instead of weight gain, by the time it was born.

Blood glucose levels should be as normal as possible during labour and childbirth, as high blood glucose levels cause increased insulin production in the unborn baby. This means that the baby will be less able to cope with the partial lack of oxygen that even a normal delivery entails. When the umbilical cord is cut, the high insulin production by the baby′s body will continue, causing the blood glucose level to drop. The child of a mother with diabetes, therefore, will be monitored carefully with extra blood glucose tests. If the baby becomes hypoglycaemic, glucose will be given intravenously. The child will also receive extra food early on, before the mother has begun to produce breast milk.

The woman′s daily insulin requirement decreases quickly after childbirth, returning to the pre-pregnant level after as little as 1 week. Breast-feeding mothers usually need to decrease their insulin doses to levels lower than they were before pregnancy to avoid hypoglycaemia. If doses are not lowered considerably, there is a clear risk of experiencing severe hypoglycaemia. After a few weeks or months, the insulin doses will usually be back to the levels they were at before the pregnancy. Breast-feeding lowers blood glucose, and a high-carbohydrate snack is often needed before or during breast-feeding. Evening or late night snacks may also be necessary.