Background Worldwide, 199.5 million women have diabetes mellitus. Preconception care education starting from adolescence has been recommended as an effective strategy for safeguarding maternal and child health. However, traditional preconception care advice provided by healthcare professionals within clinic settings is hindered by inadequate resources, sub-optimal coverage and busy clinics. eHealth which is instrumental in solving problems around scarce health resources could be of value in overcoming these limitations, and be used to improve preconception care and pregnancy outcomes for women with diabetes mellitus. Objective Objectives were to: (1) identify, summarise and critically appraise the current methods of providing PCC education, (2) examine the relationship between preconception care educational interventions (including use of technology as an intervention medium) on patient and behavioural outcomes, and (3) highlight limitations of current interventions and make recommendations for development of eHealth in this field. Method Electronic databases, using predefined search terms for preconception care education in women with type 1 or 2 diabetes mellitus, were searched for quantitative studies from 2003 until June 2016. Of the 1,969 titles identified, 20 full papers were retrieved and 12 papers included in the review. Results The reviewed studies consistently reported that women receiving educational interventions via healthcare professionals and eHealth had significantly improved levels of glycosylated haemoglobin (P<.001 and P<.0001) with fewer preterm deliveries (P=.02) and adverse fetal outcomes (P=.026). Significant improvements in knowledge (P<.001) and attitudes to seeking preconception care (P=.003) and, fewer barriers (P<.001) were also reported. Conclusion Preconception care has a positive effect on pregnancy outcomes for women with diabetes mellitus. However, uptake of preconception care is low and the use of eHealth applications for preconception care of women with diabetes mellitus still in its infancy. Initial results are promising but further research, incorporating smartphones and apps, is needed. Clearly, there is much to be done if the full potential of eHealth preconception care to improve obstetric outcomes for women with diabetes mellitus is to be realised.