Tanweer Ahmad, Imtiaz Hussain Siddiqi.
Ultrasonorgraphic assessment of Gestational age with distal femoral and proximal tibial ossification centers.
Pak Postgrad Med J Jan ;12(4):170-2.

The sonographic assessment of distal femoral and proximal Tibial ossification centers in 150 normal pregnant women was carried out between 28-40 weeks gestation. The mean gestational age for distal femoral ossification center was about 34 weeks, while mean gestational age for proximal tibial ossification center was 38 weeks. The distal femoral epiphyseal center was not visible at or before 28 weeks but was observed in 70% of fetuses at 33 weeks and 92% of fetuses at 34 weeks gestation. In 85% of fetuses with gestational age more than 33 weeks the size of epiphysis was 1 to 2 mm. Where as the size of epiphysis 3 mm or more was associated with gestational age of > 37 weeks in 86% of fetuses. The proximal tibial ossification center was not observed before 34 weeks of gestation but it was observed in 55% of fetuses at 36 weeks and 100% of fetuses at 40 weeks. The size of proximal tibial epiphysis of 1-2 mm was related to gestational age of > 36 weeks in 88% of fetuses, where as size measuring 3 mm or more was associated with gestational age of >38 weeks in 92% fetuses. The sonographic assessment of distal femoral and proximal tibial epiphyseal centers can be used as independent markers for the estimation of gestational age during third trimester.

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