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Effects of fetal intravenous glucose challenge in normal and growth retarded fetuses
U Nicolini1, C Hubinont, J Santolaya
1Royal Postgraduate Medical School, Institute of Obstetrics and Gynaecology, Queen Charlotte's Maternity Hospital, London, United Kingdom.
Insights
Intrauterine growth retardation (IUGR) fetuses exhibit a low energy state, with impaired insulin response to glucose challenges. Glucose supplementation may worsen acidosis in these fetuses.
Area of Science:
- Perinatal Medicine
- Fetal Physiology
- Endocrinology
Background:
- Intrauterine growth retardation (IUGR) is associated with altered fetal metabolism.
- Understanding fetal glucose metabolism is crucial for managing IUGR.
- Fetal blood sampling (FBS) allows direct assessment of fetal physiological parameters.
Purpose of the Study:
- To investigate fetal glucose metabolism and insulin response in IUGR fetuses.
- To compare glucose tolerance between IUGR and control fetuses.
- To assess the impact of glucose challenge on fetal acid-base balance in IUGR.
Main Methods:
- Fetal intravenous glucose challenge test performed in 9 fetuses (5 controls, 4 IUGR) between 26-33 weeks gestation.
- Fetal blood sampling via ultrasound-guided umbilical vein needling.
- Assay of fetal glucose, insulin, and acid-base balance at multiple time points post-glucose infusion.
Main Results:
- IUGR fetuses had lower basal pO2, pH, glucose, and insulin.
- Following glucose challenge, IUGR fetuses showed delayed glucose clearance and no insulin response.
- Significant difference in fetal pH change between groups, correlated with basal pO2.
Conclusions:
- IUGR fetuses demonstrate a compromised metabolic state and impaired insulin secretion.
- Fetal glucose supplementation is unlikely to be beneficial and may worsen acidosis in IUGR.
- Results support the concept of a low energy state in severe IUGR.
Abstract:
Fetal intravenous glucose challenge test (0.75 g/kg of estimated fetal weight) was performed at 26-33 weeks gestation in 9 patients undergoing fetal blood sampling (FBS) by ultrasound guided needling from the umbilical vein. The indication for FBS was rapid karyotyping for fetal malformations in 5 (control group) and severe intrauterine growth retardation in the remaining 4 (IUGR group). Fetal blood samples were taken before the glucose infusion and after 1, 3, 5, 10 and 15 min; glucose and insulin were assayed on each occasion and acid-base balance at 0 and 5 min. Basal fetal pO2, pH, glucose and insulin were lower in the IUGR group than in controls. Following the glucose challenge, fetal glucose levels were similar in the two groups, but in the IUGR group the latter part of the glucose curve was characterized by a slower and delayed return to basal levels. In control fetuses the insulin response following the glucose challenge peaked at 3 min while in IUGR no change in insulin concentration was detected. Fetal pO2 did not change in either group; the median change in fetal pH was significantly different between the two groups (controls: +0.01; IUGR: -0.04; P less than 0.05) and there was a significant correlation between basal pO2 and the change in fetal pH (r = 0.79) (P less than 0.02). These results support the concept of a low energy state in IUGR. Fetal glucose supplementation in IUGR is unlikely to be of benefit and may even exacerbate underlying acidosis.