SCI-TECH & AGRI

Diabetes prevention starts in womb

The foetus secretes extra insulin to handle abnormal glucose input from the mother. This results in the birth of big babies.

The foetus secretes extra insulin to handle abnormal glucose input from the mother. This results in the birth of big babies.  

Elevated maternal blood glucose causing gestational diabetes is first diagnosed during pregnancy. It puts the foetus at risk of developing the disease later.

BONNY NEWBORN babies weighing more than 4 kg are health personified. Heavier and bigger the baby, healthier it is. So people think. This notion is not difficult to comprehend. After all underweight babies are synonymous with intrauterine malnutrition.

But herein lies a big paradox — big size of the baby (doctors call it macrosomia) is not always a sign of healthiness. On the contrary it may be an indication of the potential risk of the baby becoming diabetic at a later stage in life. Underweight babies suffering from malnutrition are also equally at risk for subsequent diabetes.

If the press has time and again highlighted the extent of injury that a pregnant woman can cause to her foetus by drinking or smoking, very little has been written about the injury inflicted on the foetus due to elevated blood glucose level. Of course the need to control it is well known in women who are already diabetic. But little is talked about the risk of healthy non-diabetic women who develop elevated glucose during pregnancy.

"More than the genetic factor it is the intrauterine environment which is more important for the baby developing diabetes at a later date," averred Dr. V. Seshaiah, Medical Director (Diabetes Unit), Apollo Hospital, Chennai. Dr. Seshaiah should after all know it better. He was the first person to indicate the need to use just one abnormal glucose level value to label a woman as suffering from Gestational Diabetes Mellitus (GDM) way back in 1982. International publications have only confirmed what he had said. A paper published in 2000 in an international journal had stated that a minor elevation in maternal glucose level especially in high-risk group (obese people, those with family history, Asian Indians etc) should be sufficient to treat them as GDM afflicted.

Elevated maternal blood glucose level has a direct effect on the increased susceptibility of the foetus developing diabetes later. In other words, prevention of diabetes (Type II) starts not when the person celebrates his/her thirtieth birthday but right at the foetal stage even before he/she is born. And the mother also runs the risk of developing full-blown diabetes if glucose level is not controlled during pregnancy.

This is just one of the fallouts of elevated glucose for the mother. But for all the problem it poses, prevention is almost a one step procedure. Monitoring blood glucose level especially during the 20-24 week (second trimester) and staggering the meal plan or medication if required.

Puzzled? Then read on to know how. GDM is first diagnosed during pregnancy and is revealed by abnormal glucose level.

A glucose tolerance test (GTT) value of more than 140 mg/dl after two hours with 75 gm of glucose is a definite indicator of GDM. This elevated glucose level has a cascading effect on the foetus as the mother's glucose enters foetal circulation.

Foetus starts to secrete insulin in response to maternal glucose feed after the eleventh week. Any abnormal amount of glucose from the mother in turn triggers the foetus' pancreas to secrete more insulin to handle the glucose load.

Though it looks like an innocent phenomenon to handle an abnormality, extra insulin secreted by the foetus has long lasting implications. For instance, insulin has a growth promoting effect and this anabolic effect produces excess growth of all organs. "This results in big babies and is equivalent to an adult becoming obese," explained Dr. V. Balaji, Consultant Diabetologist, Apollo Hospital, Chennai. Incidentally, not always does the excess insulin produced result in big babies. At times a normal baby may also be delivered. But these babies may have abnormal visceral fat hanging in the abdominal area that is equally dangerous.

Incidentally, all pregnant women have 10-15 per cent lower blood glucose compared to their pre-pregnancy level. This reduction in the glucose level seen in the early weeks of pregnancy can be attributed to certain hormones (oestrogen and progesterone) facilitating extra insulin production and also increasing the insulin sensitivity in the body. Add to this the selective nutrition transfer from the mother to the foetus. Here, certain amino acids that act as a substrate for producing glucose is transferred to the foetus. As this transfer continues, the mother lacks the substrate needed to make glucose and this ultimately results in lesser fasting glucose level in the first trimester.

This phenomenon continues even as the pregnancy progresses to second trimester. But the action of other hormones like lactogen, cortisol that come into play nullifies this and actually causes a reduction in insulin sensitivity.

This increases the blood glucose level. In normal pregnant women this increase in blood glucose is handled by increased secretion of insulin. Some pregnant women fail to secrete the additional insulin required to take care of the elevated glucose in the blood. "This leads to abnormal glucose tolerance," Dr. Balaji said. "And the end result is gestational diabetes in these pregnant women."

While the reduced glucose level during the first trimester poses no problem to the foetus, the elevated glucose level during the second trimester finds its way into the foetus triggering more insulin production by the foetus. "It is for this reason that blood glucose level should be checked during the second trimester (20-24 weeks)," Dr. Seshaiah pointed out. Belated detection and action up to 32nd week can help minimize the effect of weight gain by the foetus.

Studies by Dr. Seshaiah and Dr. Balaji at Stanley Medical College, Chennai and similar work by other doctors at Madras Medical College, Chennai, CMC, Ludhiana and SUT Hospital Thiruvananthapuram have shown GDM incidence in pregnant women to be 15-17 per cent.

This may indeed translate into equal percentage of babies born every year with a strong predisposition to become diabetic before they turn thirty. "I was alarmed when my study found a high incidence rate," Dr. Seshaiah noted. Similar incidence rate reported by other groups have only confirmed his worst fear.

Can this be prevented at the first place? Yes. And all that is needed is timely action taken by their mothers even before the babies are born.

This is the first time the incidence of GDM has been documented in India. It should help sensitise both the mothers and doctors about the extent of the GDM prevalence and take preventives measures. Now don't blame the press for not forewarning you.

R. Prasad

in Chennai

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