First Do No Harm: Intrapartum Calcium Loading During Oxytocic Induction of Labor

Abstract

Pregnancy advancing beyond 40 completed weeks is associated with increased physical risk to both mother and fetus that increases concurrently with gestation. The recommended management for pregnancies approaching 42 weeks is a post-dates induction of labour. While induction often involves several stages, the majority of women are ultimately subject to exogenous oxytocin administration. Stringent guidelines are in place for oxytocin administration, to control the known risks associated with the use of exogenous oxytocics. Despite these measures, exogenous oxytocin is the drug most commonly associated with adverse perinatal outcomes, and is attributable to approximately half of obstetric liability claims in the United States. Further, little research exists regarding the longitudinal effects of administration of exogenous oxytocin prior to or during birth. Ionised calcium has been demonstrated to play a pivotal role in myometrial contractility through a variety of mechanisms, as demonstrated by the efficacy of calcium channel blockers as a tocolytic. Additionally, changes in calcium metabolism and sequestration during pregnancy and birth have the capacity to create a subclinical hypocalcaemia, effecting the process and progress of parturition. This paper aims to review the known risks and benefits of labour induction and exogenous oxytocin administration, and to explore the potential for its longitudinal effects. Existing research regarding induction of labour and endogenous enhancement of parturient processes will be discussed, with a particular focus on the role of calcium in labour, its physiological contribution, and the efficacy of intrapartum calcium loading in the clinical setting. Overall this paper aims to reignite discussion as to the potential supportive role calcium may play in reducing the quantity of synthetic oxytocin administered in the management of prolonged pregnancy.