Measurement of the Fetal Occiput-Spine Angle during the First Stage of Labor as Predictor of the Outcome of Labor

INTRODUCTION

The World Health Organization (WHO) describes normal birth as "spontaneous in onset, low risk in the beginning of labor, and remaining so during labor and delivery." In the vertex position the infant is born spontaneously, between 37 and 42 weeks of pregnancy. At birth, mum and baby are in good health.¹

The favorable outcome for most pregnancies is spontaneous vaginal delivery, without obstetric intervention. Nonetheless, in the second stage of labor, some women fail to make progress and thus require operative delivery. Management strategies involve primary Cesarean section, instrumental delivery (forceps or vacuum).²

In the vertex presentation, the vertex is flexed in such a way that the chin rests on the fetal chest, causing

the suboccipito-bregmatic diameter of around 9.5 cm across the maternal pelvis to be the widest diameter.

This is the smallest of the diameters used to negotiate maternal pelvis.³

Deflexed cephalic presentation is an important cause of obstructed labor as a result of labor arrest, accounting for one third of cesarean deliveries.⁴

Traditionally, three types of deflexed cephalic malpresentations, including sinciput, brow, and face, are defined by the degree of head extension. ⁵

The accurate determination of the position of the fetal head and the required application of the instrument are an important determinant of the effective and secure use of vacuum and forceps in instrumental delivery. In a high proportion of cases, the correct fetal position is not identified by the digital examination prior to instrumental delivery.⁶

In a recent study, several ultrasound parameters including progression angle, head-symphysis distance and head-perineum distance, showing strong correlations and moderate correlations with each other with the fetal head-station evaluation digital inspection.⁷

 Measuring the angle of progression over time can be a predictor of the initiation of spontaneous labor. Women who witnessed spontaneous labor onset within seven days had a substantially greater angle of progression than those who have undergone labor after seven days. In the next 7 days, a greater angle of progression is an indication of spontaneous labor.The angle of progression is also negatively associated with the length of the cervix and positively associated with the gestational age.⁸

At the first stage of labor, the fetal head attitude (fetal head-to-spin relationship) may have a significant effect on the outcome of labor. Traditionally, theprognosis ofdeflection of the fetal head is based on the examination of digital labor, even though; ultrasound was recently reported to be used to support clinical diagnosis.⁹

The aim of this research was to measure the degree of fetal head deflexionby the use of ultrasonography during the first labor stage and to quantify whether an ultrasound-derived parameter (the occiput-spine angle) has a relation to the course and the result of the labor. To decrease hazards of obstructed labor which   carry risk on both mother and fetus.

PATIENTS AND METHODS

After ethical committee approval, a total of 200 women of 37 weeks or more with gestational age and one vaginal delivery history were assessed in this study in Alhussin Hospital University by 2 dimensional ultrasound. Examinations were performed after a verbal consent from the patient with the patient lying in the dorsal supine position.

All patients selected for our study were subjected to the following:Verbal informed consent.Full history taking (age, parity, LMP, medical and surgical history). General examination including BMI, vital signs, abdominal and pelvic examination.In the first stage of labor, 2D trans-abdominal ultrasound was performed.

When the anterior occiput is the fetal position and the vertex is the fetal presentation, in the ultrasound machine, the bi-dimensional sagittal image of the fetal head and the upper spine was acquired and processed.The offline angle calculation of the tangential line to the occipital bone and the tangential line to the cervical spine of the first vertebral body (occiput-spine angle) will be performed in this image to determine the degree of flexion of the fetal head relative to the trunk. The sonographer did not engage in the patient's treatment and was blinded to the ultrasound findings and the occiput-spine angle by the obstetrician in charge.Progress of labor with partogram(cervical dilation, effacement, consistency, position and station) and mode of delivery were evaluated retrospectively for each patient in the study group.

In multipara, extended first stage of labor is characterized as cervical dilatation < 1.5 cm / h for 2 hours while the first stage arrest is characterized as non-progress of cervical dilatation for > 4 hours despite sufficient uterine activity (3-5 contractions per 10 minutes). In multipara, extended second stage of labor is characterized as fetal head descent < 2 cm / h, while the second stage arrest is characterized as no of fetal head fall after one hour, or two hours with epidural analgesia in multipara.Neonatal assessment: Follow up the neonate for Apgar score at 5 min.

Criteria for inclusion: between the ages of 18 and 35 years. BMI is under 30. About 37-42 weeks of gestational age (calculated using LMP or 1^sttrimesteric U/S). Singleton pregnancy.A history of one vaginal deliveries. Occiputo anterior position.Active first stage of labor phase.

Criteria for exclusion: age (under18 or over 35). Primigravida.Occiputo posterior position.Cesarean section signs such asmalpresentations, macrosomia, placenta previa, previous cesarean section.A lot of gestation. Disorders of health, such as hypertension, DM, liver or kidney disease.

Statistical analysis: Statistically the data were described as mean ± standard deviation (± SD), median and range, or frequency (number of cases) and, where appropriate, percentage. Numerical variables were compared using the Student t test for independent samples between study groups.For the comparison of categorical data, the Chi-square (c2) test was performed. Where the predicted frequency is less than 5, the exact test was used instead. Using the terms sensitivity and specificity, accuracy was represented.The receptor operator characteristic (ROC) analysis was used to determine the optimum cut-off value to be tested for the diagnostic markers. P values below 0.05 were referred to as being statistically significant. All statistical analyses were carried out with SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL, USA) release 15 for Microsoft Windows (2006).

RESULTS

Table 1:  Comparison between OSA

This table shows highly statistically significant difference between OSA

Table 2: Comparison between OSA

This table shows highly statistically significant difference between OSA

Table 3: Comparison between OSA

This table shows highly statistically significant difference between OSA

Table 4: Comparison between OSA

This table shows highly statistically significant difference between OSA

Table 5: Comparison between OSA

This table shows highly statistically significant difference between OSA