Tocolysis is an important procedure in obstetrics used to delay preterm delivery. Tocolytics are medications used in achieving postponing preterm delivery mainly by reducing uterine contractility, hence, reducing perinatal morbidity and mortality. Different biologic proteins are involved. This essay discusses the effects of various biologic receptors and proteins on uterine relaxation, and their possible tocolytic mechanisms. These include the beta (β) adrenergic receptors, anoctamin-1, calcium channel antagonists, calmodulin, cyclo-oxygenase (COX) 1 and 2, amongst others. The articles used for this review covered the period up to 2022, and over 180 articles were obtained following literature search and of these, 64 were adapted for this article. Others whose scope were not relevant to the review were excluded. The articles were retrieved following searches using search engines and databases including Medline, Elsevier, Medscape, eMedicine, Google and PubMed. Understanding the mechanisms of tocolytic effects will benefit exploring more therapeutic ways of inducing uterine relaxation in improving pregnancy outcomes, thus resulting in decline of fetal morbidity and mortality.