The association between an incomplete placenta and postpartum haemorrhage (PPH) is well documented; however, the significance of ragged or incomplete membranes has not been explored as an independent risk factor for PPH.

To explore the association between the completeness of the amniotic and chorionic membranes and the risk of PPH, independent to placental status.

Materials and methods
37 176 birth records were retrospectively extracted from the period 1 July, 2008 to 30 June, 2016 from the databases of two public hospitals in Melbourne, Australia. Following application of specific exclusion and inclusion criteria, including non‐complete placentas, 5718 records were available for analysis. These records were grouped based on membrane status (complete, ragged or incomplete) and outcome (PPH or no PPH).

Primary PPH rates were 14.8% in women with complete membranes, 20.2% in women with ragged membranes and 25.8% in women with incomplete membranes. Following statistical adjustment, the risk ratios for PPH were 1.32 (95% CI: 1.15–1.50) and 1.70 (95% CI: 1.41–2.04) in women with ragged and incomplete membranes, respectively.

Both ragged and incomplete membranes were found to be independent risk factors for primary PPH. This previously un‐discussed association has the potential to influence clinical practice changes, particularly with regard to the ongoing clinical relevance and use of the terms ‘ragged’ and ‘incomplete’ membranes.