RESUMEN
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. MATERIAL AND METHOD: 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 compared 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 placental 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.