Effects of pre-pregnancy care for women with type 1 or type 2 diabetes: a systematic review

Background Women with pre-existing diabetes face a markedly increased risk of adverse pregnancy outcomes. Advances in diabetes management and a rising prevalence of type 2 diabetes during pregnancy underscore the need to reassess the effectiveness of care provided before conception. This review examined the impact of such care on maternal and perinatal outcomes in pregnancies affected by type 1 diabetes or type 2 diabetes. Methods We systematically identified studies comparing women who received structured care before conception with those who did not. Two reviewers independently screened records, extracted data, and assessed risk of bias. Owing to substantial heterogeneity in study design and definitions of care, findings were synthesized narratively by outcome domain and diabetes type. Results Fiftyone studies were included, predominantly involving women with type 1 diabetes or populations including both diabetes types. Pre-pregnancy care was consistently associated with lower glycated hemoglobin levels in early pregnancy, while differences later in gestation were smaller and less consistent. Several studies suggested reduced risk of congenital malformations and perinatal mortality, though results varied and were often constrained by sample size and residual confounding. Pre-pregnancy care may also facilitate earlier antenatal care and reduce miscarriage risk, whereas evidence for other maternal and neonatal outcomes was inconsistent. Conclusions Pre-pregnancy care remains an important strategy for improving outcomes in pregnancies complicated by pre-existing diabetes despite advances in diabetes care. However, effect estimates varied across studies, and evidence in type 2 diabetes was particularly limited, underscoring the need for contemporary studies focusing on this growing population.