Fetal Growth Restriction was a Major Cause of Increased Perinatal Mortalities of Postterm Pregnancies

Seo, Kyung; Won, Hyung Jae; Cho, Jae Sung; Park, Yong Won; Kim, Sei Kwang; Lee, Kook

Abstract

OBJECTIVE
Perinatal mortality rates were higher in postdate than in term pregnancies. Previous study showed the risk to be greater in postterm newborns weighing less than 2500 grams at birth. This study is designed to examine the effect of gestational age and fetal growth restriction (FGR) on the perinatal mortalities of the postterm pregnancies.
METHODS
Maternal and perinatal database of Yonsei University Medical Center from 1961 to 1990 was reviewed. After excluding pregnancies with known medical or obstetrical complications, we compared perinatal mortality rates of 39,631 singleton pregnancies delivered between 37 weeks and 44 weeks of gestational age according to the birthweight percentile. Birth weight percentile were grouped as FGR1 (<5 percentile), FGR2 (5-10 percentile), and adequate for gestational age (AGA) (>10 percentile). Mortalities were compared using Chi-square statistics.
RESULTS
Mean birth weight increased up to 42 weeks of gestation. Perinatal mortalities increased after 42 weeks of gestation. FGR1 group showed higher perinatal mortality rate compared with AGA group at 41 weeks of gestation (135/8, p<0.01). At 42 weeks of gestation, both FGR1 and FGR2 showed increased perinatal mortality rates (130/10 p<0.01, 56/10 p<0.01). Among AGA group, mortality increase was not obvious up to 42 weeks of gestation.
CONCLUSION
Fetal growth restriction was a major cause of increased perinatal mortalities in postterm pregnancies.