TOPLINE:

In nulliparous women at term who required assisted vaginal birth, a non-rotated occipitoposterior position of the foetal head was associated with significantly higher rates of maternal morbidity than prior rotation to an occipitoanterior position. Neonatal morbidity outcomes were not affected by the foetal head position.

METHODOLOGY:

• Researchers conducted secondary analyses of a randomised controlled trial and a cohort study to assess outcomes associated with assisted vaginal birth in an occipitoposterior foetal head position.
• They included 1081 nulliparous women at term with singleton cephalic pregnancies who were assessed for assisted vaginal birth in the second stage of labour.
• Of 1081 assisted vaginal births, 192 (17.8%) had an occipitoposterior position before attempting assisted vaginal birth; of these, 103 (53.6%) rotated successfully to an occipitoanterior position before birth, whereas 89 (46.4%) remained at the same position.
• Maternal and neonatal morbidity outcomes with an occipitoposterior foetal head position in which the foetal head was successfully rotated to an occipitoanterior position were compared to those with the position remained occipitoposterior.

TAKEAWAY:

• Assisted vaginal birth with the foetal head in an unrotated occipitoposterior position was associated with higher rates of postpartum haemorrhage (adjusted odds ratio [aOR], 3.57; P < .001), obstetric anal sphincter injury (aOR, 12.62; P = .001), and caesarean section (aOR, 8.99; P < .001) than that with the foetal head in an occipitoposterior position rotated to an occipitoanterior position.
• The occipitoposterior position was misdiagnosed as an occipitoanterior or occipitotransverse position in 18.2% of cases, which did not significantly affect morbidity outcomes compared to correctly diagnosed cases.
• Neonatal outcomes, such as birth trauma, low Apgar score, foetal acidosis, and NICU admission, did not differ by the foetal head position at birth.

IN PRACTICE:

"Our data suggest that there is increased maternal morbidity associated with AVB [assisted vaginal birth] completed in a non-rotated (direct) OP [occipitoposterior] position and that this should be balanced with the risks of CS [caesarean section] in the second stage of labour," the authors wrote.

SOURCE:

This study was led by Lauren Hayes, The Coombe Hospital & Trinity College, University of Dublin, Dublin, Ireland. It was published online on September 14, 2025, in BJOG: An International Journal of Obstetrics & Gynaecology.

LIMITATIONS:

The study sample was not sufficient to address less common adverse neonatal outcomes, such as encephalopathy, and may have lacked power to evaluate neonatal trauma. The observational nature of the study explored associations rather than causation. Differentiating between the misdiagnosis of the foetal head position and suboptimal instrument placement was challenging, particularly in vacuum-assisted births.

DISCLOSURES:

The trial was funded by the Health Research Board of Ireland. One author reported providing medicolegal expert opinions, including aspects of assisted vaginal birth.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.