Fetal rotation examined with ultrasound

Abstract

We would like to thank Patji Alnæs-Katjavivi for his interest and comments on our article and for referring to the recently published work of VanSickle et al. challenging the myth of the perfect obstetric pelvis.^{1, 2} The aim of our study was to examine fetal rotation longitudinally with ultrasound in a sub-Saharan population. We observed a higher rate of persistent occiput posterior position at birth than reported in studies mainly comprising white European women.³

The shape of the birth canal has been thought to influence fetal rotation. Four classical pelvic shapes were described in the 1930s, but demarcations between these are not clear. Variations with regard to pelvic shape between ethnicities have been published and referred to in our article. However, the evidence on this is from old studies as pointed out by Alnæs-Katjavivi, and we agree that paying attention to the pelvic shape has limited clinical value. The clinical examination of the female pelvis is unreliable. The obstetrical conjugate can be measured with ultrasound (recently published),⁴ and also the sub-pubic arch angle can be measured.⁵ However, these measurements do not provide information on the shape of the pelvis and assessing this was not an objective in our study. Our focus was on the process of rotation, to what degree this occurred in the study population, and what effects fetal rotation had on labor outcome.

It is important to identify women at risk for arrested labor in a reliable way and these women should have added surveillance in labor. Persistent occiput posterior position is associated with prolonged labor and operative interventions,⁶ as also shown in our study.³ Timely diagnosis of this is important and ultrasound is a valuable tool to make this possible. We showed a proportional difference between our study population and what has been assumed before. We acknowledge that this observation calls for more information about fetal rotation from other populations in Africa as well as from different parts of the world.

In our setting, maternal mobility, including ambulation, squatting, and the use of birthing balls, is encouraged during the active first and early second stages of labor to promote fetal rotation and descent. Continuous midwifery care is provided, sometimes with a companion, but not on a one-to-one basis.

Our main clinical message is thus to recommend the active use of ultrasound during labor for diagnosing rotation failure. This will lead to enhanced surveillance and appropriate management of persistent occiput posterior positions, while also helping to avoid unnecessary interventions in women with the fetus in the occiput anterior position.

Laerdal Foundation for Acute Medicine.