Routine Gestational Diabetes Screening Could Improve Health Outcomes for Mothers and Babies

Gestational diabetes (GD) screening is something that varies from place to place, with some places testing routinely, and others testing only those with risk factors. This is a condition that arises during pregnancy and affects both mother and baby, yet screening and testing approaches are inconsistent across the UK and around the world. But should testing be routine? What are the benefits, and what are the risks?

What is Gestational Diabetes, and What Causes It?

GD is a condition that occurs during pregnancy, although it is not entirely similar to diabetes type 1 and type 2. Unlike type 1 and type 2 diabetes, GD does not persist after diagnosis — rather, it ends when the pregnancy ends.

It is caused by the placenta releasing hormones which impair normal insulin function, causing the body to end up with excess sugar in the bloodstream. This sugar is transferred to the baby, and has flow-on effects that can affect the health of the baby and the labour and birth process. Some people are more at risk of getting GD, including those who are overweight or obese, those who have had a big baby in the past (over 4.5kg), and those of certain ethnicities such as Middle Eastern, Asian, and African-Caribbean ethnicities. If the mother’s family has a history of type 1 or type 2 diabetes, she may also be more at risk.

Is Screening Really Necessary?

Most medical professionals agree that gestational diabetes screening of some kind is important, though there are those who disagree in particular with the glucose tolerance test (GTT) approach to screening. The GTT is administered by giving the patient a sugary glucose drink, with blood tests taken before and after the drink is consumed. The level of sugar present in the patient’s blood after the drink has been consumed is measured, and if it is above a certain threshold the patient may be asked to repeat the test at a later date, or will be diagnosed with GD at that point if the sugar levels are extremely high. As GD impairs normal insulin function, those with GD will have higher levels of blood sugar than those who don’t have GD.

A representative from a law firm that handles pregnancy care claims explained that in the UK, pregnant mothers are screened for GD during pregnancy in some places but not in others, despite health professionals being aware of the risks involved with GD. This lack of consistent diagnosis can leave some mothers and babies at risk, and awareness must be raised about this issue so that more mothers can be screened in future.

The downsides of the GTT approach to screening are that the sugar threshold is not consistent across countries and the level of sugar consumed is significant. It is not uncommon to vomit after consuming the glucose drink, and some mothers even faint. The other factor at play is that screening those without risk factors may put an unnecessary burden on the health system, with the cost of the GTT being administered to those who are unlikely to have GD at all.

What are the Risks of Not Being Screened?

Despite the downsides of administering the screening test, not administering it may have far worse outcomes. GD comes with few or no symptoms, which means a mother going undiagnosed may have serious consequences for both her and her baby.

Typically, GD is treated by either dietary measures or medication, to ensure that the mother’s blood sugar levels stay consistent and not too high. If these measures are not in place due to a lack of diagnosis, the baby can grow large with the excess sugar in the baby’s blood being converted to fat. This is called macrosomia, and can cause complications during the labour and birth such as shoulder dystocia (getting stuck in the birth canal). If GD has been diagnosed, many mothers are induced early to prevent such complications.

Furthermore, even if there is no macrosomia or shoulder dystocia present, and the baby is born at an average weight for gestational age, there can be blood sugar issues that occur after the baby is born and is no longer receiving a supply of high-sugar blood from the mother. If the GD has been untreated, the baby’s body has become accustomed to this high sugar level, and produces high amounts of insulin to deal with it. When the baby is born, the high insulin production remains, but not the high sugar levels. This can cause the baby to end up with low blood sugar (hypoglycemia), from the excess insulin processing the normal blood sugar too quickly. Hypoglycemia can result in the baby having seizures and other serious problems, so babies born to mothers with GD are closely monitored after birth and may spend time in NICU. If GD has not been diagnosed, the healthcare team will not know to be aware of these potential problems.

It’s clear that GD can come with major complications, even more so if the mother has gone undiagnosed. There are some downsides of performing the GTT, but at the end of the day the screening does help to protect mothers and babies, and should be offered routinely. Those opposed to the GTT can always ask to undertake regular finger prick monitoring of blood sugar instead, to ensure that they receive the best care during their pregnancy. Routine offering of the GTT will reduce patchy coverage for those without risk factors, and will stop outliers from being missed.

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