Maternal and neonatal outcomes following abnormally invasive placenta: a population-based record linkage study.

INTRODUCTION: Abnormally invasive placenta involves abnormal adherence of the placenta to the myometrium and is associated with severe pregnancy complications such as blood transfusion and hysterectomy. Knowledge of outcomes has been limited by small sample sizes and a focus on maternal rather than neonatal outcomes. This study uses population-level data collected over 10 years to investigate maternal and neonatal outcomes and trends in incidence of abnormally invasive placenta (also known as placenta accreta, increta and percreta).

MATERIAL AND METHODS: A population-based record linkage study was performed, including all women who gave birth in New South Wales, Australia, between 2003 and 2012. Data were obtained from birth records, hospital admissions and deaths registrations. Modified Poisson regression models, adjusted for confounding factors, were used to quantify the effect of abnormally invasive placenta on adverse maternal and neonatal outcomes.

RESULTS: Abnormally invasive placenta was significantly associated with morbidity for mothers (adjusted relative risk 17.6, 99% confidence interval 14.5-21.2) and infants (adjusted relative risk 3.1, 99% confidence interval 2.7-3.5). Abnormally invasive placenta increased risk of stillbirth (relative risk 5.4, 99% confidence interval 4.0-7.3) and neonatal death (relative risk 8.0, 99% confidence interval 1.5-41.6). The overall rate of abnormally invasive placenta was 24.8 per 10 000 deliveries, and 22.7 per 10 000 among primiparae. Incidence increased by 30%, from 20.6 to 26.9 per 10 000, over the 10-year study period.

CONCLUSIONS: Abnormally invasive placenta substantially increases the risk of severe adverse outcomes for mothers and babies, and the incidence is increasing. Delivery should occur in tertiary hospitals equipped with neonatal intensive care units. Clinicians should be cognizant of the risks, particularly to infants, and maintain a high index of suspicion of abnormally invasive placenta, including in primiparae.