"High pre-pregnancy HbA1c is challenging to improve and affects insulin requirements, gestational length and birth weight"

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BACKGROUND: The aim of this study was to explore how pre-pregnancy HbA1c affects the course of HbA1c and insulin requirements during pregnancy, the gestational length and birth weight METHOD: An observational cohort study was conducted, consisting of 380 women with type 1 diabetes who gave birth 530 times from 2004 to 2014. The participants were divided into 4 groups according to pre-pregnancy HbA1c.

RESULTS: HbA1c was significantly different between the groups at all time-intervals from week 5-10 to week 33-36 (p ≤ 0.01). In Group 1, with the lowest pre-pregnancy HbA1c (< 6.5% (48 mmol/mol)), HbA1c stayed at the same level throughout pregnancy. In the other groups (G2: 6.5% (48 mmol/mol) to 7.9% (63 mmol/mol); G3:8% (64 mmol/mol) to 9.9% (86 mmol/mol) and G4: > 10% (86 mmol/mol)) a decrease in HbA1c was seen in early pregnancy but stabilized from mid-pregnancy onwards. Group 1 had the lowest daily insulin requirements throughout pregnancy among the four groups (p = 0.001). The relationship between birth weight and pre-pregnancy HbA1c was found to be inversely U-shaped. Mean gestational length in Group 4 was significantly shorter than Group 1 (p = 0.001).

CONCLUSIONS: In this very large cohort, we found that a poor pre-pregnancy HbA1c is a predictor for poor glycemic control during pregnancy and that HbA1c decreases until mid-pregnancy and then plateaus. A very poor pre-pregnancy HbA1c is associated with shorter gestational length and lower birth weight, which is contrary to the common assumption that poor glycemic control leads to higher birth weight.

HIGHLIGHTS: In this very large cohort of 530 pregnancies in women with T1DM, we found that a high pre-pregnancy HbA1c is a predictor for sub-optimal glycemic control during pregnancy and that HbA1c only decreases until mid-pregnancy and then plateaus. In addition, a very high pre-pregnancy HbA1c is associated with shorter gestational length and lower birth weight Z-score, which is contrary to the common assumption of poor glycemic control leading to higher birth weight.

OriginalsprogEngelsk
TidsskriftJournal of Diabetes
Antal sider9
ISSN1753-0393
DOI
StatusE-pub ahead of print - maj 2020

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