Diabetes and pregnancy

During a normal pregnancy, many maternal physiological changes occur and there is an increase in insulin needs[1] due to increased hormonal secretions that regulate blood glucose levels, glucose-'drain' to the fetus, slowed emptying of the stomach, increased excretion of glucose by the kidneys and resistance of cells to insulin.

The risks of maternal diabetes to the developing fetus include miscarriage, growth restriction, growth acceleration, fetal obesity (macrosomia), mild neurological deficits,[2] polyhydramnios and birth defects.[3]In some studies 4% to 11% of infants born to type 1 diabetic women had defects compared to 1.2% to 2.1% of infants born in the general population.[4] The cause is, e.g., oxidative stress, by activating protein kinase C[5] that leads to apoptosis of some cells.[5] A hyperglycemic maternal environment has also been associated with neonates that are at greater risk for development of negative health outcomes such as future obesity, insulin resistance, type 2 diabetes mellitus, and metabolic syndrome.[6]

During the first trimester, besides increased birth defect risks, having a miscarriage is also increased due to abnormal development in the early stages of pregnancy.[7]

When blood glucose is not controlled, shortly after birth, the infant's lungs may be under developed and can cause respiratory problems.[3] Hypoglycemia can occur after birth if the mother's blood sugar was high close to the time of delivery, which causes the baby to produces extra insulin of its own.

Mild neurological and cognitive deficits in offspring — including increased symptoms of ADHD, impaired fine and gross motor skills, and impaired explicit memory performance — have been linked to pregestational type 1 diabetes and gestational diabetes.[8][9][10] Prenatal iron deficiency has been suggested as a possible mechanism for these problems.[11]

Birth defects are not currently an identified risk for the child of women with gestational diabetes, since those primarily occur in the latter part of pregnancy, where vital organs already have taken their most essential shape.

High blood sugar levels are harmful to the mother and her fetus. Experts advise diabetics to maintain blood sugar level close to normal range for 2 to 3 months before planning for pregnancy. Managing blood sugar close to normal before and during pregnancy helps to protect the health of mother and the baby.

Insulin may be needed for type 2 diabetics instead of oral diabetes medication. Extra insulin may be needed for type 1 diabetics during pregnancy. Doctors may advise to check blood sugar more often to maintain near-normal blood sugar levels.

Blood glucose levels in pregnant woman should be regulated as strictly as possible. Higher levels of glucose early in pregnancy are associated with teratogenic effects on the developing fetus.[12] A Cochrane review published in 2016 was designed to find out the most effective blood sugar range to guide treatment for women who develop gestational diabetes mellitus in their pregnancy. The review concluded that quality scientific evidence is not yet available to determine the best blood sugar range for improving health for pregnant women with diabetes and their babies.[13]

During the first weeks of pregnancy less insulin is required due to tight blood sugar control as well as the extra glucose needed for the growing fetus.[14] At this time basal and bolus insulin may need to be reduced to prevent hypoglycemia. Frequent testing of blood sugar levels is recommended to maintain control. As the fetus grows and weight is gained throughout the pregnancy, the body produces more hormones which may cause insulin resistance and the need for more insulin.[14] At this time it is important for blood sugar levels to remain in range as the baby will produce more of its own insulin to cover its mother's higher blood sugar level which can cause fetal macrosomia.[15] During delivery, which is equivalent to exercise, insulin needs to be reduced again or hyperglycemia can occur. After the baby is delivered and the days following, there are no more hormones from the placenta which demanded more insulin, therefore insulin demand is decreased and gradually returns to normal requirements.[3]

Diabetes mellitus may be effectively managed by appropriate meal planning, increased physical activity and properly-instituted insulin treatment. Some tips for controlling diabetes in pregnancy include:

• Cut down sweets, eats three small meals and one to three snacks a day, maintain proper mealtimes, and include balanced fiber intake in the form of fruits, vegetables and whole-grains.
• Increased physical activity - walking, swimming/aquaerobics, etc.
• Monitor blood sugar level frequently, doctors may ask to check the blood glucose more often than usual.
• The blood sugar level should be below 95 mg/dl (5.3 mmol/l) on awakening, below 140 mg/dl (7.8 mmol/l) one hour after a meal and below 120 mg/dl (6.7 mmol/l) two hours after a meal.
• Each time when checking the blood sugar level, keep a proper record of the results and present to the health care team for evaluation and modification of the treatment. If blood sugar levels are above targets, a perinatal diabetes management team may suggest ways to achieve targets.
• Many may need extra insulin during pregnancy to reach their blood sugar target. Insulin is not harmful for the baby.

Breast feeding is good for the child even with a mother with diabetes mellitus. Some women wonder whether breast feeding is recommended after they have been diagnosed with diabetes mellitus. Breast feeding is recommended for most babies, including when mothers may be diabetic. In fact, the child's risk for developing type 2 diabetes mellitus later in life may be lower if the baby was breast-fed. It also helps the child to maintain a healthy body weight during infancy. However, the breastmilk of mothers with diabetes has been demonstrated to have a different composition than that of non-diabetic mothers, containing elevated levels of glucose and insulin and decreased polyunsaturated fatty acids.[16] Although benefits of breast-feeding for the children of diabetic mothers have been documented, ingestion of diabetic breast milk has also been linked to delayed language development on a dose-dependent basis.[16]

In some cases, pregnant women with diabetes may be encouraged to express and store their colostrum during pregnancy, in case their blood sugar is too low for feeding the baby breast milk after birth.[17] There is no evidence on the safety or potential benefits when pregnant women with diabetes express and store breast milk prior to the baby's birth.[17]

The White classification, named after Priscilla White[18] who pioneered research on the effect of diabetes types on perinatal outcome, is widely used to assess maternal and fetal risk. It distinguishes between gestational diabetes (type A) and diabetes that existed before pregnancy (pregestational diabetes). These two groups are further subdivided according to their associated risks and management.[19]

There are 2 classes of gestational diabetes (diabetes which began during pregnancy):

• Class A₁: gestational diabetes; diet controlled
• Class A₂: gestational diabetes; medication controlled

The second group of diabetes which existed before pregnancy can be split up into these classes:

• Class B: onset at age 20 or older or with duration of less than 10 years
• Class C: onset at age 10-19 or duration of 10–19 years
• Class D: onset before age 10 or duration greater than 20 years
• Class E: overt diabetes mellitus with calcified pelvic vessels
• Class F: diabetic nephropathy
• Class R: proliferative retinopathy
• Class RF: retinopathy and nephropathy
• Class H: ischemic heart disease
• Class T: prior kidney transplant

An early age of onset or long-standing disease comes with greater risks, hence the first three subtypes.

• Diabetes mellitus
• Gestational diabetes
• Pregnancy

• CDC’s National Center on Birth Defects and Developmental Disabilities