Interpretation (in light of other evidence)
Non-occiput anterior (transverse or posterior) positions are associated
with a high risk of cesarean section, operative vaginal delivery and
other peripartum complications, including third- or fourth-degree
perineal lacerations, postpartum hemorrhage and chorioamnionitis13, 18, 40, 41. Compared with neonates born in the OA
position, neonates born in a non-occiput anterior position have a lower
Apgar score, a higher risk of neonatal intensive care unit admissions
and higher rates of birth trauma 18, 19. The incidence
of persistent OP position is between 5% and 12% 12,
18, 42, and that of persistent OT position varies from 3% to 8%13, 40, 43. A study by
Petitjean
et al. 44 identified oxytocin augmentation, excessive
gestational weight gain, direct OP position and macrosomia as
independent factors associated with non-OA to OA rotation during the
first stage of labor. In our study, maternal height is the single
individual factor associated with internal fetal occiput rotation. On
the other hand, the degree of fetal head rotation, as measured by the
MLA, was parallel between vaginal and cesarean delivery groups at first.
However,
the MLA of the women who experienced vaginal delivery was narrower
subsequently, indicating the occurrence of spontaneous rotation.
Moreover, we develop a simple model based on the intrapartum sonographic
parameter and maternal
characteristic
to predict spontaneous fetal head rotation in the first stage of labor.
We think this finding might provide the clinicians an opportunity to
take earlier action to reduce the obstetric complications associated
with persistent OP and OT positions.
Accumulating studies showed that maternal and neonatal characteristics,
including parity, maternal age, height, BMI, neonatal birth weight and
fetal head position, are independent factors that affect the mode of
delivery 28, 45, 46. Burke et al. 47reported a risk prediction model for cesarean delivery using five
parameters (maternal age, height, BMI, fetal head circumference and
fetal abdominal circumference), with excellent discrimination
(Kolmogorov- Smirnov, D statistic, 0.29; 95% CI, 0.28-
0.30).
Furthermore, Eggebø et al. 39introduced
intrapartum ultrasound to developed
another
risk score based on maternal characteristics (gestational age, maternal
weight, BMI and cervical dilatation), occiput position and intrapartum
findings (head perineal distance and caput succedaneum) to predict
vaginal birth, which yielded an AUC of 0.853 (95%CI, 0.678-1.000). Our
study illustrated a much simple prediction model based on only two
parameters (maternal stature and AoP) for
evaluating
the delivery mode in the nulliparas in the first stage of labor. We
started the intrapartum ultrasound assessment during the latent phase
(cervical dilatation less than 6 cm), which allowed clinicians to
identify early the women who required cesarean delivery. We caution that
the
knowledge
derived from our model should not alter obstetric decision making.
However, our study might provide useful information about the chance of
spontaneous rotation and vaginal birth, allowing
appropriate
interventions
at the proper time.
CONCLUSION
In conclusion, our study
provides
simple models based on maternal characteristics and intrapartum
ultrasound findings that can predict the chance of vaginal birth and
successful internal fetal head rotation in nulliparous women.
We
suppose these models can be implemented in any delivery unit.