Placental Weight and Its Ratio to Birth Weight in Normal Pregnancy at Songkhlanagarind Hospital
Manop Janthanaphan MD*, Ounjai Kor-anantakul MD*, Alan Geater PhD**
Affiliation : * Department of Obstetrics and Gynecology, Faculty of Medicine, Prince of Songkla University, Songkhla ** Epidemiology Unit, Faculty of Medicine, Prince of Songkla University, Songkhla
Objectives : To quantify placental weight and its ratio to birth weight in normal pregnancy; and to determine
whether abnormal placental weight and its ratio are associated with poor pregnancy outcomes.
Design : Prospective, cross-sectional study.
Materials and Methods : From January 1st, 2004, to December 31st, 2004, placentae were obtained from 238
normal pregnancies, between the 36th-40th gestational weeks. The trimmed and drained placenta was weighed
and the mean placental weight at term was defined. Distribution curves for placental weight and their ratios
with gestational age were constructed. The outcomes for the intrapartum and perinatal periods were com-
pared with normal placental weight, its ratio to the group above the 90th percentile and below the 10th
percentile. Fisher’s Exact Test was used to analyze the data. A p value < 0.05 was considered significant.
Results : The placental weight increased according to the birth weight (r = 0.450, p < 0.005). The mean placen-
tal weight at 36-40 gestational age was 519 g (SD = 89.01g). The mean placental weight to birth weight ratio
was 17.08%. This ratio decreased slightly with advancing gestational age. There was an association between
placental weight below the 10th percentile and fetal distress (p = 0.003). Placental weight to birth weight
ratio below the 10th percentile was also associated with fetal distress (p = 0.02). Placental weight above the
90th percentile was associated with newborns requiring neonatal intensive care admission (p = 0.016).
Conclusion : The placental weight increased according to the birth weight.The placental weight to birth
weight ratio decreased slightly with advancing gestational age.Abnormal placental weight and its ratio were
significantly associated with some adverse pregnancy outcomes.
Keywords : Placental weight, Birth weight, Pregnancy outcomes
