The perinatal period is an important time for infant and parent. Vulnerable parents with pre-existing challenges, such as adverse experiences in their own childhood, might find the transition to parenthood particularly hard. The Cochrane Review considered here sought to assess the effectiveness of parenting interventions provided to parents with symptoms of complex post-traumatic stress disorder and/or a history of childhood maltreatment, with the aim of improving the parents’ well-being or parenting capacity. In this commentary we focus on how the limited evidence base, along with some key aspects of the review’s methodology, might have influenced its finding that such interventions showed little or no benefit.