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Glycaemic Control in Women With Type 1 Diabetes and Preeclampsia Risk: A Nationwide Cohort Study
Natalie Holowko1,2,3, Nathalie Roos1, Björn Pasternak1,4
1Clinical Epidemiology Division, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden.
Objective:
No large-scale studies exist investigating glycaemic control around conception and preeclampsia risk.
Design:
Population-based nationwide cohort study using the National Diabetes Register and other health registers.
Setting:
Sweden.
Population:
Singleton pregnancies between 2003 and 2019 (N = 1 689 301); 4429 with type 1 diabetes (T1DM) and 1 684 872 without.
Methods:
The main exposure was having a pre-gestational diagnosis of T1DM (first diagnosis anytime ≤ 91 days after conception and ≥ 1value of glycated haemoglobin (HbA1c) within ±90 days from conception). Peri-conceptional glycaemic control was categorised using the most recent HbA1c measurement (mmol/mol: < 48; 48-61; 62-75; ≥ 76). Unexposed were women without any diabetes diagnosis (≤ 91 days after conception).
Main Outcome Measures:
Preeclampsia was defined using ICD codes and further categorised according to completed gestational weeks at delivery with preeclampsia diagnosis: early preterm preeclampsia (< 34 + 0), late preterm preeclampsia (34 + 0 to 36 + 6), or term preeclampsia (≥ 37 + 0).
Results:
16.8% of women with T1DM developed preeclampsia, compared to 2.9% of women without diabetes (adjusted RR [aRR] 4.7, 95% CI 4.4-5.0). Preeclampsia risk increased with peri-conceptional HbA1c, from 11.6% in women with HbA1c < 48 mmol/mol to 23.3% in women with HbA1c ≥ 76 mmol/mol. Compared to unexposed women, there was a dose-response relationship between HbA1c and preeclampsia in women with T1DM (HbA1c < 48 mmol/mol aRR 3.4 (2.9-4.0); HbA1c 48-61 mmol/mol aRR 4.6 (4.2-5.1); HbA1c 62-75 mmol/mol aRR 5.7 (5.0-6.5): HbA1c ≥ 76 mmol/mol aRR 6.3 (CI 5.3-7.7)). Compared to unexposed women, the aRR of term preeclampsia was 3.5 times higher (3.1-3.9) in women with T1DM, while the aRR was much higher for early preterm preeclampsia (aRR 7.2: 6.1-8.5) and late preterm preeclampsia (aRR 9.9: 8.8-11.1).
Conclusions:
Women with T1DM had a higher risk of preeclampsia, which increased in a dose-response manner with poorer peri-conceptional glycaemic control.
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