Placenta accreta: we can do better!

Abstract

Abnormally invasive placenta (AIP) is a morbid obstetric disorder with dramatically high rates of haemorrhage and associated complications such as disseminated intravascular coagulation, multi-system organ failure, need for hysterectomy and death. However, owing to the relative rarity of the condition in any single medical centre, quality data are hard to come by. In this issue of BJOG, L Thum et al. provide data from a population-based study of AIP in the Nordic countries (Lindqvist et al. BJOG 2016; 123:1348–55). They make several important observations. First, they confirm the well-known associations between placenta praevia, previous caesarean delivery, previous uterine surgery and AIP. In addition, they identify a novel risk factor, previous postpartum haemorrhage (relative risk 6.5, 95% CI 3.7–10.9). This is biologically plausible and has not been previously described. Second, a relatively high proportion of cases (70%) were not diagnosed before delivery. It has been shown that complication rates are significantly lower with antenatal diagnosis of AIP, especially for those delivered in specialised referral centres (Silver et al. AJOG 2015;212:561–8). Strategies to enhance antenatal diagnosis include increased awareness of risk factors among clinicians. In addition to pregnancies with placenta praevia and previous caesarean delivery, those with previous uterine surgery, especially endometrial ablation, previous postpartum haemorrhage and perhaps in vitro fertilisation should be screened for AIP. The authors suggest that additional studies are needed to assess the cost-effectiveness of targeted screening for AIP in various subgroups. However, it is possible to effectively screen for AIP without adding cost or burden to women or the healthcare system. Almost all women in high-income countries have at least one antenatal sonogram that includes an evaluation of the placenta. It requires minimal additional burden to assess for sonographic evidence of AIP in women with risk factors. In such women it is important for the clinician ‘reading’ the study to comment on level of suspicion for AIP in the report. Only women with sonographic suspicion of AIP or a placenta that overlies a uterine scar require additional subsequent studies to assess for AIP. We routinely do this in our centre with minimal additional cost or burden. Perhaps the most striking finding of the study is the relatively low rate of AIP in Nordic countries. Although they probably had ‘under-ascertainment’ due to imperfect surveillance and the use of somewhat rigorous criteria, the incidence is still substantially lower than in the USA. Assuredly this is due in part to lower rates of caesarean delivery and high-order caesarean delivery in Nordic countries. However, there may be other reasons for the dramatically varied rates noted in high-income countries. First, it is necessary to standardise the definitions of AIP used in different hospitals, countries and studies. Second, it is possible that differences in maternal characteristics as well as obstetric care (e.g. caesarean technique) contribute to varied rates of AIP. It is necessary to use the ‘natural experiment’ of varied AIP rates to better understand the pathophysiology of AIP. Finally, the strategy most certain to help reduce the rate of AIP continues to be avoidance of unnecessary caesarean delivery. None declared. Completed disclosure of interests form available to view online as supporting information. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.