Biparietal diameter Archives - Revista Brasileira de Ginecologia e Obstetrícia

Purpose: to estimate growth curves and tables of average biparietal diameter and average head circumference of twin gestations and to compare them with published growth curves for singletons and twins. Methods: growth curves and tables of average biparietal diameter and average head circumference were obtained from sonographic examinations of 34 patients with twin gestations without maternal and fetal complications. Sonographic examinations were performed each 2 or 3 weeks by a single observer. The parameters were compared with existing growth curves for singletons and twins. Results: curves and tables of biparietal diameter and head circumference in relation to gestational age were obtained. The study revealed difference in growth pattern mainly regarding the 3rd trimester in relation to singletons (Hadlock et al.15). The difference between the average values were 6 mm (biparietal diameter) and 2.0 cm (head circumference) at the 39th week of gestation. Also, some differences were observed relative to the twin studies. Conclusion: this study revealed that growth curves for average biparietal diameter and average head circumference of singletons are not appropriate to determine gestational age in twin gestations of the studiced population principally at the 3rd trimester