Introduction
Placental abruption is a significant obstetric complication that affects both maternal and neonate mortality and morbidity. It is defined as the premature partial or total separation of a normally implanted placenta.1 Maternal consequences include excessive blood loss and disseminated intravascular coagulation (DIC), which sometimes needs blood transfusion and can lead to hypovolemic shock, multiorgan failure, peripartum hysterectomy, and rarely, death.2,3 Neonatal consequences include preterm birth and related hypoxia or an asphyxia condition.1,4 Fetal asphyxia combined with prematurity can be associated with short-term sequelae such as neonatal encephalopathy/hypoxic-ischemic encephalopathy and long-term sequelae such as cerebral palsy, lung diseases, and epilepsy.1,5
The prevalence of placental abruption varies across regions. In some countries, the prevalence of placental abruption is increasing, possibly due to changes in the risk factors,2 including increasing maternal age, body mass index, and increasing use of assisted reproductive technology (ART) since the past decade. Maternal age is one of the key risk factors for placental abruption. In 1993, a prospective cohort study comprising 30,681 participants with singleton pregnancies reported that the risk of placental abruption increased in a year (odds Ratio [OR] 1.03, 95% confidential interval [CI] 1.00–1.06, p = 0.04).6The statistic reports suggest that the mean maternal age is increasing in Japan.7Although a recent Japanese birth cohort study reported that increasing maternal age is a risk factor for preterm delivery and fetal growth restriction,8teenage maternal age is also a risk factor for severe maternal obstetric complications such as hypertensive disorders of pregnancy (HDP) and placental abruption.9 Owing to the changes in social background during the last decade, up-to-date evidence for the effect of maternal age on placental abruption is required.
Several studies have focused on the advanced maternal age as a risk factor for placental abruption. However, a few prospective studies have comprehensively assessed both teenage and advanced maternal age as risk factors for placental abruption, while accounting for several confounding factors using a large number of participants. Therefore, the present study, including the participants from the largest prospective birth cohort study in the Japanese population conducted between 2011 and 2014, examined the effect of maternal age on placental abruption.