BACKGROUND
No previous study has evaluated the transitions of intrapartum transperineal ultrasound
parameters during labor progression in cephalic malposition.
OBJECTIVE
We aimed to quantitate the characteristic trends of fetal head position and descent
in cephalic malposition by analyzing the transitions of intrapartum transperineal
ultrasound parameters and explore an indicator associated with the degree of cephalic
malposition.
STUDY DESIGN
We retrospectively analyzed pregnant women who delivered at term from January 2018
to December 2020 at the University of Tokyo Hospital. The fetal occipital position
was classified as occiput anterior and nonocciput anterior according to the fetal
occipital angle of 0° to 75° and 75° to 180°, respectively. Fetal occipital angle
was defined by the midline angle and position of the ocular orbit. The differences
in the trends of head direction, head–symphysis distance, and progression distance
relative to the angle of progression between occiput anterior and nonocciput anterior
cases were evaluated. In addition, the parameters that showed differences were analyzed
to evaluate their relationship to the degree of cephalic malposition.
RESULTS
A total of 502 images (occiput anterior, 319; nonocciput anterior, 183) met the inclusion
criteria. The distribution of head direction values relative to the angle of progression
was smaller in the nonocciput anterior group than in the occiput anterior group, whereas
the head–symphysis distance and progression distance values relative to the angle
of progression showed no difference in their distribution between the occiput anterior
and nonocciput anterior groups. The ratio of head direction to the angle of progression
was significantly smaller in the nonocciput anterior group than in the occiput anterior
group (median [interquartile range], 0.03 [−0.02 to 0.10] vs 0.21 [0.12–0.28]; P<.0001). Furthermore, this ratio was negatively correlated with fetal occipital angle
(Spearman correlation coefficient, −0.66).
CONCLUSION
Our results indicated that the head direction to angle of progression ratio reflects
the deviation in the fetal head direction toward the maternal dorsal side, and decreases
in proportion to the degree of cephalic malposition. This concept of deviation in
the head direction as an indicator for evaluating cephalic malposition with intrapartum
transperineal ultrasound may contribute to improving labor management in the case
of cephalic malposition.
Key words
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Article info
Publication history
Published online: September 22, 2022
Accepted:
September 19,
2022
Received:
September 13,
2022
Footnotes
The authors report no conflict of interest.
The authors declare no funding for this study.
Cite this article as: Yano E, Iriyama T, Sayama S, et al. The head direction to the angle of progression ratio: a quantitative parameter for intrapartum evaluation of cephalic malposition. Am J Obstet Gynecol MFM 2022;XX:x.ex–x.ex.
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