Research Implications and recommendations
Our data are among the first to suggest a link between intrauterine
resting tone during labor and neonatal outcomes. We hypothesize that
this is a result of persistent utero-placental hypoperfusion during
labor due to limited recovery of uterine and spiral artery blood flow
between contractions. However, this hypothesis will need to be tested
with future clinical and mechanistic studies. The most relevant and
urgent research directions to consider are whether duration of elevated
intrauterine resting tone affects neonatal outcomes and to determine a
more precise definition of “elevated” resting tone, rather than our
empiric cutoff of >75th percentile.
Additionally, studies examining whether any interventions, such as
positional changes or intermittent pushing during second stage of labor,
can decrease intrauterine resting tone and subsequently fetal morbidity,
are needed.
We found that induction of labor, which applied to 58% of patients in
the cohort, was less common among women with elevated resting tone.
Similarly, women with elevated resting tone were less likely to receive
oxytocin and had lower maximum doses of oxytocin during their labor.
Despite fewer interventions, women with elevated resting tone were more
likely to have a vaginal delivery. These findings suggest that higher
resting tone may be a surrogate for more efficient uterine contractility
and labor. However, since women in this cohort had an indication for
IUPC placement, most likely due to dysfunctional labor, these findings
need further assessment in a non-biased cohort. Further research is
needed to determine the association between elevated resting tone,
uterine contractility and labor progress.