Perinatal Backgrounds and NICU Bed Occupancy of Multiple-Birth Infants in Japan.

Multiple pregnancies (twin, triplet, and higher-order pregnancy) are associated with an increased risk of resultant preterm and low birth weight infants. The increase of multiple pregnancies for several decades in Japan has been an important consideration in bed allocation planning for neonatal intensive care unit (NICU). The guideline of the Japan Society of Obstetrics and Gynecology (JSOG) in 2008 recommended that embryo transfer be limited to one. The epidemiological data of Japanese regional multiple pregnancies before the JSOG recommendation are valuable in assessing the perinatal effects after this recommendation. The aim of this study was to investigate regional backgrounds of multiple pregnancies and neonatal outcomes of multiple births including NICU admission before the JSOG recommendation. This is a retrospective population-based study for 20 months (January, 2007 through August, 2008) in Shiga Prefecture, Japan. Sending questionnaires to institutions treating multiple births in Shiga, we extracted relevant data from the responses of respective obstetricians and neonatologists. There were 245 multiple births including 241 twins and 4 triplets. We found more twin deliveries with higher risks such as monochorionic diamniotic twins or preterm twins less than 34 weeks in hospitals including perinatal centers than in primary obstetrics clinics. More than half of multiple-birth infants (57%) required NICU admission, and nearly 20% of NICU beds in Shiga are occupied with multiple-birth infants. Furthermore, half of multiple-birth infants were conceived with medical assistance. We conclude that multiple pregnancies resulting from medically assisted conception could have a significant impact upon the NICU bed occupancy in Japan.