Ultrasound growth parameters in relation to levels of amniotic fluid insulin in women with diabetes type-I

Biomarkers for Macrosomia Prediction in Pregnancies Affected by Diabetes

Large birthweight, or macrosomia, is one of the commonest complications for pregnancies affected by diabetes. As macrosomia is associated with an increased risk of a number of adverse outcomes for both the mother and offspring, accurate antenatal prediction of fetal macrosomia could be beneficial in guiding appropriate models of care and interventions that may avoid or reduce these associated risks. However, current prediction strategies which include physical examination and ultrasound assessment, are imprecise. Biomarkers are proving useful in various specialties and may offer a new avenue for improved prediction of macrosomia. Prime biomarker candidates in pregnancies with diabetes include maternal glycaemic markers (glucose, 1,5-anhydroglucitol, glycosylated hemoglobin) and hormones proposed implicated in placental nutrient transfer (adiponectin and insulin-like growth factor-1). There is some support for an association of these biomarkers with birthweight and/or macrosomia, although current evidence in this emerging field is still limited. Thus, although biomarkers hold promise, further investigation is needed to elucidate the potential clinical utility of biomarkers for macrosomia prediction for pregnancies affected by diabetes.

Amniotic fluid insulin levels and fetal abdominal circumference at time of amniocentesis in pregnancies with diabetes

AIMS

Fetal hyperinsulinism is a strong predictor for excessive growth and fetopathy in pregnancies complicated by diabetes. We examined (i). the relationship between measurements of amniotic fluid insulin (AF insulin) and fetal abdominal circumference (AC) at the time of amniocentesis, and (ii). whether there is a threshold for fetal AC percentiles which can identify low vs. high-risk levels of AF insulin without performing an amniocentesis.

METHODS

In a retrospective study, AF insulin from 121 pregnant diabetic women (32 pregestational; 89 gestational) was measured during the 3rd trimester as part of a diabetes management protocol. AC measurements were transformed into a continuous variable of percentile growth for gestational age (Hadlock). Division of the cohort according to deciles or quartiles of AC percentiles was performed to identify a threshold AC with a significant increase in elevated AF insulin, previously defined as AF insulin >or= 7 microU/ml. A receiver operator characteristic (ROC) curve was created and the negative predictive value (NPV) of the determined threshold was calculated.

RESULTS

AF insulin levels were significantly correlated with the AC percentiles (r = 0.3, P = 0.0005) by linear regression. No AC threshold could reliably identify a moderate elevated AF insulin >or= 7 microU/ml (NPV 77.2%), but an AC threshold >or= 75th percentile could identify with fetal hyperinsulinism with an AF insulin >or= 16 microU/ml. All 10 cases of AF insulin >or= 16 microU/ml were identified with a NPV of 100% (74/74).

CONCLUSIONS

Our data indicate that an AC >or= 75th percentile determined by a 3rd trimester ultrasound examination may discriminate between pregnancies at low vs. high risk for AF insulin >or= 16 microU/ml. This AF insulin concentration corresponds to a level of hyperinsulinism reported to be associated with considerable neonatal and long term morbidity.

Amniotic fluid insulin levels identify the fetus at risk of neonatal hypoglycaemia

AIMS

To investigate the use of amniotic fluid insulin (AFI) as a predictor of neonatal morbidity in the macrosomic newborn of the diabetic mother, in view of the fact that raised AFI levels are a marker for fetal hyperinsulinaemia.

METHODS

AFI was measured by radioimmunoassay in a group of pregnant diabetic women (n = 63) with normal (n = 41) or accelerated fetal growth (n = 22).

RESULTS

Using log transformed data, liquor insulin was found to be significantly higher in pregnant women with Type 1 and Type 2 diabetes mellitus (17.6 mU/l; 95% confidence interval (CI) 11.7-26.4) compared with women with gestational diabetes mellitus (GDM) (8.2 mU/l; 95% CI 4.8-13.8, P = 0.02) or impaired glucose tolerance (IGT) (6.2mU/l; 95% CI 4.9-8.0, P = 0.0001). In the group with macrosomic fetuses (birth weight > 90th centile for gestational age), there was a significantly higher incidence of elective Caesarean section (CS) and emergency CS (12/22) compared to those with appropriate for gestational age (AGA) fetal weights (birth weight > 10th and < 90th centiles for gestational age) (9/41, P = 0.009). There was no significant correlation between raised AFI and macrosomia except in the Type 1 diabetic women, in whom the AGA group mean was 13.2 mU/l (95% CI 7.4-23.3), and 34.6mU/l (95% CI 17.5-68.4 P = 0.022) in macrosomia. In the latter group, hypoglycaemia requiring treatment was significantly more common in the macrosomic hyperinsulinaemic neonates (8/13), compared to normoinsulinaemic neonates in the same group (0/9, P = 0.005).

CONCLUSIONS

Identification of the hyperinsulinaemic fetus before delivery might allow the intensification of maternal insulin therapy leading to a reduction in incidence and severity of diabetic fetopathy. Pregnancy with a normoinsulinaemic fetus could be allowed to continue to the onset of spontaneous labour, which might result in a lower CS rate.