Aim. Recent studies have shown that women with hyperglycaemia in pregnancy and insulin resistance have a greater risk of adverse pregnancy outcomes than women with normoglycaemic pregnancies. This study aimed to determine adverse pregnancy outcomes of women with hyperglycaemia in pregnancy only as a function of insulin resistance.

Methods. From a prospective cohort study, we included 1,423 women with hyperglycaemia in pregnancy whose insulin resistance was evaluated using homoeostatic model assessment for insulin resistance (HOMA-IR) when care was first provided for this condition. We compared the adverse pregnancy outcomes for different tertiles of HOMA-IR (intertertile range 1.9 and 3.3).

Results. Increasing HOMA-IR tertiles were positively associated with the rate of insulin therapy (tertile 1, 2 and 3: 32.7, 47.0 and 58.7%, P < 0.0001), caesarean section (23.7, 26.0 and 32.2%, respectively, P < 0.01), gestational hypertension (1.3, 2.8 and 5.4% respectively, P < 0.01), preeclampsia (1.5, 2.8 and 4.5% respectively, P < 0.05), large-for-gestational-age infant (13.3, 10.4 and 17.6% respectively, P < 0.05), and neonatal hypoglycaemia (0.8, 1.5 and 3.2% respectively, P < 0.05). Women in the 3rd HOMA-IR tertile were more likely to have insulin therapy (odds ratio 2.09 (95% interval confidence 1.61–2.71)), hypertensive disorders (2.26 (1.42–3.36)), and large-for-gestational-age infant (1.42 (1.01–1.99)) than those in the 1st and 2nd tertiles combined in multivariable logistic regression analyses adjusted for gestational age at HOMA-IR measurement, glycaemic status, age, body mass index, family history of diabetes, parity and ethnicity.

Conclusion. Despite suitable care and increased rates of insulin therapy during pregnancy, higher insulin resistance in women with hyperglycaemia in pregnancy was associated with a greater risk of adverse pregnancy outcomes.