For pregnant women with diabetes, some particular challenges exist for both mother and fetus. If the pregnant woman has diabetes as a pre-existing disorder, it can cause early labor, birth defects, and larger than average infants. Therefore, experts advise diabetics to maintain blood sugar level close to normal range about 3 months before planning for pregnancy.
When type 1 diabetes mellitus or type 2 diabetes mellitus is pre-existing, planning in advance is emphasized if one wants to become pregnant, and stringent blood glucose control is needed before getting pregnant.
Physiology
Pre-gestational diabetes can be classified as Type 1 or Type 2 depending on the physiological mechanism. Type 1 diabetes mellitus is an autoimmune disorder leading to destruction of insulin-producing cell in the pancreas; type 2 diabetes mellitus is associated with obesity and results from a combination of insulin resistance and insufficient insulin production. Upon becoming pregnant, the placenta produces human placental lactogen (HPL), a hormone with counter-regulatory actions leading to increased blood glucose levels. In combination with pre-existing diabetes, these maternal physiological changes can lead to dangerously high blood glucose levels. This is significant because the consequences of poor glycemic control are more severe during pregnancy compared to non-pregnant states.
Risks for the fetus
The negative effects of pregestational diabetes are due to high blood sugar and insulin levels primarily during the first trimester of pregnancy (in contrast to gestational diabetes, which can lead to fetal complications during the second and third trimester). Since this period is when many of the major internal structures and organs of the fetus is decided, pre-existing diabetes can lead to congenital abnormalities. These include abnormal development of the heart and the central nervous system (brain and spinal cord). Strong correlations have been reported between diabetes and sacral agenesis, holoprosencephaly, and longitudinal limb deficiency. With regards to the heart, increased likelihood of truncus arteriosus, atrioventricular septal defect, and single ventricle complex has been found. It is important to note that these complications are generally rare and can be averted with tight blood sugar control. 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.
Pre-existing diabetes can also lead to complications in the neonate after birth, including neonatal jaundice, hypoglycemia, and macrosomia. Pregestational diabetes does not, however, increase the likelihood of diseases due to chromosomal alterations (e.g., Down Syndrome). Furthermore, miscarriages are also increased due to abnormal development in the early stages of pregnancy.
Furthermore, when blood glucose is not controlled, shortly after birth, the infant's lungs may be under developed and can cause respiratory problems. 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. 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.
Diabetes pregnancy management
Blood glucose levels in pregnant women should be regulated as strictly as possible. During the first weeks of pregnancy less insulin treatment is required due to tight blood sugar control as well as the extra glucose needed for the growing fetus. 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. 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. 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.