Pregnant diabetics have to be vigilant as failure to control their blood glucose can lead to miscarriages and stillbirths.
DIABETES mellitus is a condition in which the blood glucose is too high (hyperglycaemia). It is due to insufficient insulin being produced or the cells in the body being unable to use insulin the way they should. Without insulin, the blood glucose that cannot get into the body’s cells accumulates in the bloodstream.
Diabetic pregnancies had invariably resulted in miscarriages or stillbirths until about three decades ago. Many diabetics get pregnant today. Although there are potential complications, a healthy baby will result, provided there is good control of the blood glucose. This can be achieved by close partnership between the patient with her obstetrician and her physician or endocrinologist.
Metabolic changes during pregnancy
There are many changes in the body during pregnancy. The placenta produces hormones essential to foetal development and they increase in the second and third trimester. They also prevent insulin from functioning the way it is supposed to (insulin resistance). Thus, the demand for increased insulin with feeding escalates progressively during pregnancy. The body has to produce about three times the normal amount of insulin to overcome the effects of the placental hormones.
The kidneys of some pregnant women may handle glucose differently from those of non-pregnant women. Glucose is excreted in the urine although the blood glucose is normal or in the absence of hyperglycaemia.
This is unrelated to diabetes, self-limiting and does not require treatment. This means that urine glucose is not a reliable method of diagnosing and monitoring diabetes.
In most women, the body produces extra insulin to maintain the blood glucose in the normal range. However, in about 5% of women, the extra insulin produced is insufficient, leading to hyperglycaemia by the 20th to 24th week of pregnancy. After delivery, the body uses insulin more effectively and the blood glucose returns to the normal range.
This condition only occurs during pregnancy and is called gestational diabetes (GDM). The risk factors for GDM include maternal age, obesity, obstetric history of diabetes or large babies and strong family of diabetes.
Good control of blood glucose is essential to maternal and foetal well-being. Poor control increases the risk of high blood pressure and the worsening of pre-existing diabetic complications like eye and kidney problems.
Poor control in the first trimester, when the foetal organs are being formed, increases the risk of birth deformities and miscarriage. Diabetic ketoacidosis, a complication due to poor control, can also lead to miscarriage. Gestational diabetics do not usually have these problems because the condition develops after the first trimester.
Poor control later in pregnancy increases the risk of foetal death and/or increased foetal growth with birth weights above 4kg (macrosomia), the incidence of which is thrice that of those with blood glucose within the normal range. Macrosomia increases complications during labour and delivery, the likelihood of instrumental vaginal delivery and caesarean section, and birth injury.
Although most diabetics have increased foetal growth, those who have vascular disease (eye or kidney complications) or high blood pressure are at increased risk of restricted foetal growth. The baby may have a low blood glucose (hypoglycaemia) at birth, which is life threatening and can affect the baby’s mental development.
The baby is more prone to jaundice and low blood calcium and magnesium. If untreated, the former leads to brain damage and the latter to spasms in the hands and feet, or twitching muscles. The diabetic foetal lungs mature later than the non-diabetic, leading to an increased risk of respiratory distress.
It is generally accepted that babies born to diabetics have twice the risk of birth injury, thrice the likelihood of caesarean section and four times the incidence of admission to the neonatal intensive care unit. The risk in individual cases is related to the degree of maternal hyperglycaemia.
Effects of pregnancy on diabetes
The body’s changes during pregnancy make control of blood glucose more difficult. During the first trimester, the insulin requirement may decrease slightly and can lead to hypoglycaemia which can affect brain function. Nausea and vomiting during this time affects carbohydrate absorption in the gut, thereby impacting on insulin dosing. Pre-existing diabetic complications may worsen during pregnancy.
Insulin requirements increase gradually between 16 to 20 weeks of pregnancy and then markedly. This is due to the placental hormones which are important for foetal growth but concomitantly, blocks the effects of insulin. The insulin requirements will be less during labour as the body is working using glucose for its energy requirements. After birth, the body’s insulin requirements decreases but it will take weeks or months before the body’s changes are complete.
Regular check-ups: A doctor examining a pregnant woman at a hospital in Kathmandu. Certain hormones that increase during pregnancy can prevent insulin from functioning the way it is supposed to.
A routine urine screen for glucose is carried out at every antenatal visit to enable the doctor to decide who needs further investigation. Gestational diabetes (GDM) is diagnosed by an oral glucose tolerance test (GTT). After an overnight fast, the patient is given a dose of oral glucose and the blood and urine checked for glucose at regular intervals.
Type 1 (insulin dependent) diabetes is usually diagnosed when there is an episode of hyperglycaemia, ketosis and coma occurring usually during childhood, adolescence or young adulthood before pregnancy. Type 1 diabetes is rarely diagnosed during pregnancy when it is usually accompanied by unexplained coma due to unstable diet and glucose control in early pregnancy.
The diagnosis of type 2 diabetes may be problematic as severe GDM may have similar characteristics. A HbA1C of 8% or more in the first trimester is highly suggestive. A definitive diagnosis can be made after delivery with a GTT.
Pre-pregnancy assessment and treatment is advisable for all diabetics and those with a history of gestational diabetes in a previous pregnancy.
The diabetes management plan during pregnancy includes: knowing and keeping the blood glucose level under control; healthy diet; regular, moderate physical activity; maintaining a healthy weight gain; taking medications as prescribed; keeping records as advised by the doctor; and keeping appointments with the doctor as advised.
The widespread availability of glucometers has revolutionised diabetic management. Recording blood glucose levels before and after meals improves glycaemic control.
The frequency and timing of blood glucose measurements are individualised by the doctor. A healthy diet comprises a balance of foods from all food groups providing the nutrients, vitamins and minerals necessary for a healthy pregnancy.
Moderate physical activity is not the same as daily routine activity. Listen to your body. It will tell how much activity is sufficient. Stop when you feel tired. If you feel dizzy or faint, stop immediately. It is important to maintain a healthy weight gain, which means overall weight gain and weekly rate of weight gain.
Insulin therapy in pregnant diabetics helps to achieve blood glucose profiles similar to that of pregnant non-diabetics. It is usually given by subcutaneous injection. The insulin regimens require combinations and timing of injections that are different from that in the non-pregnant state.
The doctor will advise on the adjustments to the insulin dosages. Because the insulin requirements change as pregnancy advances, the insulin injections will have to be continually modified. This requires meticulous attention to detail by both patient and doctor.
Insulin therapy is helpful in treating some gestational diabetics to achieve a positive outcome. The obstetric management includes: monitoring foetal growth and wellbeing; preventing maternal complications; preventing stillbirth and asphyxia; and minimising maternal and foetal morbidity at delivery.
The timing of delivery is important as the objectives are to prevent stillbirth and asphyxia and to minimise morbidity to mother and baby. Delivery that is as near to the expected date of delivery increases the likelihood of spontaneous labour and vaginal delivery. However, the risks of increasing foetal macrosomia, birth injury and stillbirth increase as one approaches the expected date of delivery.
The obstetrician considers several factors when deciding on the timing and mode of delivery. They include blood glucose control, maternal complications, foetal macrosomia and foetal biophysical profile.
The patient’s preference is also considered but in this situation, lesser weightage is placed on it when compared to other factors. It would be prudent to adhere to medical advice.
Despite the challenges, good blood glucose control leads to a satisfactory outcome for both mother and baby.
Source: Dr Milton Lum