Morphometric Study of Subpubic Angle in Human Fetuses.

INTRODUCTION: The symphysis pubis is formed at the confluence of the pubic bones. Each pubic bone consists of a body and two rami; the superior ramus is joined with the ilium and the inferior ramus with the ischium. The two bones meet in the midline at the pubic symphysis. The two inferior rami at the lower border of pubic symphysis subtend the subpubic angle. In females the subpubic angle is more than 90° and in males it is less than 90°. Most of the previous studies on the subpubic angle have been in children or adults, therefore data on fetuses did merit.

AIM: The aims of the present study were to measure the subpubic angle in developing human fetuses of different gestational age, whether it is sex dependent and to compare the results with that in the adults.

MATERIALS AND METHODS: A cross-sectional study conducted in the Department of Anatomy JN Medical College, AMU Aligarh, over a period of two years. A total of 41 fetuses immersion fixed in 10% formalin were obtained from the museum department of anatomy. For the purpose of study fetuses were divided into five groups according to gestational age. Group I comprises fetuses of 14-18weeks, group II 19-22weeks, group III 23-26weeks, group IV 27-30weeks, groupV >30weeks of gestation. Pubic symphyses were dissected, cleaned and subjected to radiological examination in the anteroposterior plane. With the help of radiographs subpubic angle was measured. Readings obtained were analysed statistically.

RESULTS: Subpubic angle ranged between 58°-64° throughout intrauterine life. Maximum angle (63°- 64°) was observed in group I and V and in the rest of the groups it was less than 60°, with highly significant (p-value<0.001) increase in the last group. Statistically significant sexual dimorphism was observed in group I and II fetuses (p-value <0.001). Subpubic angle was more in females during the first half and in the terminal part of gestation.

CONCLUSION: Subpubic angle remained acute throughout the intrauterine life, with significant widening in fetuses more than 30 weeks of gestation. Marked sexual dimorphism was noticed only in fetuses of 14-18 weeks and 19-22 weeks of gestation fetuses, although the values were invariably less than 90° (acute) in both the sexes but in females towards the higher side as in adults. Assessment of symphysis and subpubic arch during antenatal ultrasonography of pregnant women can be done to diagnose congenital widening of the symphysis or absence of symphysis altogether.