The invention relates to the method for treatment, diagnosis and prevention of diseases related to fetal growth and placental insufficiency and comprises methods including inhibiting or increasing relaxin synthesis, relaxin receptor synthesis, relaxin binding to the relaxin receptor, and relaxin receptor activity. The invention also relates to screening assays to identify compounds that modulate relaxin and/or relaxin receptor activity. The invention further relates to gene therapy methods utilizing relaxin and relaxin-related sequences for the treatment and prevention of diseases related to fetal growth and placental insufficiency.