1.0 Introduction
Primary postpartum haemorrhage (PPH) is one of the most common complications of childbirth and a major cause of maternal mortality and morbidity worldwide.(1-5) The World Health Organization (WHO) defines primary PPH as a maternal blood loss ≥ 500 mL within the first 24 hours of giving birth.(4, 5) Women who experience a primary PPH commonly require greater levels of clinical intervention and care immediately after the birth of their child and into the postpartum period.(6)
The most common cause of primary PPH is uterine atony contributing to 70-80% of all primary PPHs.(2) In high income countries such as Australia, France, Canada, the United Kingdom (UK) and the United States of America (USA) there has been an increased incidence of primary atonic PPH in the last 10-20 years.(3, 6-9) However, this increase is not fully explained with changes in known risk factors or reporting.(3)
One intervention that is anecdotally considered a potential risk factor for primary PPH is the administration of intravenous (IV) fluids during labour. The use of IV fluids as part of labour care is common in high income countries such as Australia, Canada, and the USA.(10-14) It is biologically plausible a potential relationship exists whereby larger volumes of IV fluids could impair uterine contractility through the development of uterine swelling (15) and/or metabolic acidosis. (16) Additionally, dilution of clotting factors (coagulopathy)(16) or endogenous oxytocin could be possible mechanisms. If true, these could contribute to atonic PPH by inhibiting the myometrium from efficiently contracting onto exposed blood vessels after placental separation and/or preventing blood to clot effectively.
The aim of this study was to investigate whether there is a relationship between the administration of IV fluids during labour and primary PPH. The primary objective was to evaluate whether the administration of high-volume IV fluids during labour (≥ 2500 mL) increases the risk of primary PPH for women with a term gestation, singleton pregnancy, in comparison to low-volume IV fluids during labour (<2500 mL).