Low Glucose Levels in Underweight Pregnant Japanese Women Associated With Smaller Babies
Small for gestational
age (SGA) refers to babies that are smaller than what is expected for their age
in weeks. More specifically, the
birthweights of SGA babies are below the 10th percentile for babies of the same
gestational age. These babies are at a higher risk of mortality and
morbidity around birth. In addition, they are more likely to develop long-term
ailments like obesity, diabetes and heart disease.
‘Underweight pregnant women with low glucose challenge test should be watched for small for gestational age (SGA) babies.’
The glucose challenge test
(GCT) is usually done between 24 to 28 weeks of pregnancy. The test is used as
a screening tool to identify gestational diabetes (diabetes
that appears during pregnancy) and type 2 diabetes in the pregnant women.
Diabetes during pregnancy can cause a
large baby and should therefore be identified and controlled early.
For the glucose
challenge test, women are given to drink a solution that contains 50mg or 75mg
glucose. A blood sample is obtained one hour later. Women whose blood glucose
levels are above normal have to undergo another test called the glucose
tolerance test (GTT) to accurately determine the presence of gestational
diabetes or
type 2 diabetes.
Sometimes, instead of calling the patient twice, doctors do a single 2-hour
glucose tolerance test. In this test, the patient is given a drink containing
75mg glucose to have in a fasting state. Blood tests are obtained before
glucose intake and hourly for two hours thereafter.
Researchers
are focusing on women who have low glucose challenge test results during
pregnancy.
It is possible that these women have increased insulin sensitivity. Insulin is
the hormone that controls blood glucose levels. The increased insulin
sensitivity can cause low glucose levels in the mother as well as the baby,
which can affect fetal growth
In a study conducted in
Japan, researchers studied the association between pre-pregnancy
BMI of the
mother and GCT done between 24 and 28 weeks of pregnancy with small for
gestation age babies.
The data for the study
was obtained from hospital records of 1860 women. The glucose challenge test in
these women was carried out between 24 and 28 weeks of gestation with 50 g
glucose. Patients with GCT of less than or equal to 90 mg/dL were considered to
have a low GCT, while those with a GCT of between 91 and 139 mg/dL were grouped
into the non-low-GCT group. Women with a higher GCT were excluded from the
study.
The women were
classified according to their pre-pregnancy body mass index into three groups -
underweight (<18.5 kg/m2), normal weight (18.5-25.0 kg/m2) and obese
(≥25.0 kg/m2).
The researchers found
that:
- Around a fifth of the women
included in the study i.e. 20.4 percent were underweight
- SGA
was more common in the low-GCT group than in the non-low-GCT group (15.5% vs
10.5%)
- When the
pre-pregnancy BMI was considered, low GCT was associated with SGA babies in the
underweight group. This association was not noted in the normal BMI and obese
groups.
The researchers suggest
that GCT may be used as test to detect possible SGA fetuses in underweight
women. Since the test is anyway done routinely, the patient does not have to
bear the cost and discomfort of an additional test.
The study does have some
limitations:
- The researchers did not consider
factors like maternal smoking, presence of kidney disease and inflammatory bowel
disease, which could have also caused SGA.
- The insulin
sensitivity was not measured during the study. The GCT may have been affected
by other conditions like age and body weight of the patient, environment,
change in life partner and situation in which the meal was consumed.
Reference
- Shinohara S, Uchida Y, Hirai M,
Hirata S, Suzuki K. Relationship between maternal hypoglycaemia and
small-for-gestational-age infants according to maternal weight status: a
retrospective cohort study in two hospitals BMJ Open 2016;6:e013749
doi:10.1136/bmjopen-2016-013749
Source: Medindia
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