Three variants of abnormally invasive placentation had recognised: placenta accreta, in which placental villi invade the surface of the myometrium; placenta increta, in which placental villi extend into the myometrium; and placenta percreta. Where the villi penetrate through the myometrium to the uterine serosa and may invade adjacent organs, such as the bladder.
Placenta accreta, increta, or percreta is associated with major pregnancy complications, including life-threatening maternal haemorrhage, large-volume blood transfusion, and peripartum hysterectomy. However, limited data exist to guide the optimal management of this condition. The existing literature consists predominately of case reports, and studies had undertaken using retrospective review of medical records. Over a number of years in a single or a small number of tertiary-care institutions.
Such studies have a number of limitations, including limited generalizability and a lack of statistical power. The aims of this study were to prospectively identify a national population-based cohort of women with placenta accreta, increta, or percreta. To describe the current management of this condition in the UK. And the associated outcomes for women and their infants, in order to inform future practice guidelines.
Cases included all women identified as having placenta accreta, increta or percreta, defined as either placenta accreta, increta, and percreta diagnosed histologically. The following hysterectomy, or post-mortem, or an abnormally adherent placenta, requiring active management. Including conservative approaches where the placenta is left in situ.
The UK Obstetric Surveillance System (UKOSS) had used to identify cases on a national basis between 1 May 2010 and 30 April 2011. Every month, report cards had sent to nominated clinicians in each obstetrician-led maternity unit in the UK, with a tick box. To indicate the number of cases of placenta accreta, increta, or percreta they had seen that month.
The clinicians have asked to return all cards, even when they had ‘nothing to report’. Data collection forms were then sent to the clinicians who reported a case to confirm the diagnosis. And request further information concerning potential risk factors, management, and outcomes.
All data requested were anonymous, and up to five reminders were sent if data collection forms were not returned. Data were double-entered into a customised database. Information on the women’s year of birth and expected date of delivery was used to identify duplicate case reports, and cases were reviewed to ensure that they met the case definition.