Comparison between Sonographic Cervical Length and Bishop Score in Preinduction Cervical Assessment prior to induction of labor as regards induction success.

Type of the study:

assessment of accuracy of diagnostic test.

Study setting:

The study will be performed at Ain Shams university Maternity hospital on nulliparous women at term admitted to causality for induction of labor.

Study population:

The study will be held on 200 women all are primigravida between 37-42 weeks gestation to whom induction of labor will be carried out in the casualty of Ain Shams University Maternity Hospital.

All patients will have cervical assessment by modified Bishop score and cervical length measurement by ultrasound.

Plan for induction of labor:

• Detailed and careful history will be taken from the participants as follows:

  1. Personal history: including name, age, occupation, residence and special habits of medical importance.
  2. Obstetric history: including gestational age and regular antenatal care.
  3. Past history: including any medical disorder e.g Diabetes mellitus, hypertension or any surgical procedure.
  4. History of present pregnancy: duration of pregnancy from last menstrual period, any complications occurred or any medication used during pregnancy.

• Examination of the participants:

  1. General examination: level of consciousness, vital data, complexion.
  2. Abdominal examination: fundal level, lie of the fetus, detection of any uterine contractions and fetal heart rate.
  3. Pelvic Examination : presenting part, presence of ruptured membranes and cervical assessment as regard cervical dilation, effacement, station and presenting part to calculate the modified Bishop Score.

• Investigations: complete blood count, blood group, non stress test.

• All women will have trans-vaginal ultrasound sound for assessment of cervical length.

• Protocol of trans-vaginal ultrasound will be as follows:

  1. Patient will be asked to void.
  2. Vaginal probe will be inserted using direct visualization.
  3. Identification of bladder and fetal presenting part.
  4. Identification of abnormal findings as placenta previa or absence of fetal heart motion.
  5. Identification of mid-line sagittal plane of the cervix and looking in the proximal one third of the image for the internal cervical os then pulling back the probe until the lightest touch provides good image of the cervical canal and moving the probe slightly to get the best long axis of the cervix then measuring the cervical length three times by placing the calibers appropriately and recording the distance between internal and external os then at last recording the measurement of the best image .

• If cervical length assessed by trans-vaginal ultrasound is less than 28 mm or modified Bishop Value is less than 7, the patient will receive 3mg prostaglandin E2 for pre-induction cervical ripening to be repeated after 6 hours with maximum of 2 doses. If failed cervical ripening, Cesarean section will be done.

• All Patients will be tested by antepartum fetal heart monitoring "Non stress test".This will be considered reactive if there are two or more fetal heart rate accelerations peaking at least by 15 beats/min above the baseline and lasting for 15 seconds or more from baseline, within a 20 minutes period, with or without fetal movement felt by the mother. A non-reactive tracing will be one without sufficient fetal heart rate accelerations over a 40 minutes period. Any patient with non-reassuring non stress test will be excluded.

• Successful induction will be defined as vaginal delivery within 24 hours.

• Failed induction after 24 hours will indicate lower segment cesarean section. Failed induction will be defined as an inability to achieve the active phase of labor corresponding to a cervical dilatation ≥4 cm within 12 hours of initiating oxytocin. Failure of progress was defined as no cervical dilatation during the active phase of labor for at least 2 hours or no descent of the fetal head during the second stage of labor for at least 1 hour despite adequate uterine contraction. This will be considered an indication for cesarean delivery.

• No further induction agent will be given when uterine contractions reach frequency of three in ten minutes each lasting 30-60 seconds with cervical changes. Amniotomy and oxytocin augmentation will begin when cervical dilation becomes > 3 cm.

• Oxytocin infusion will be prepared by placing 5 IU ampoule in 500 ml Ringer or Saline to achieve concentration of 10 ml\minute.

• The rate of infusion will be started at a rate of 5 miu/ml (about 10 drops per minute) and will be increased at same increment every 20 minutes according to uterine contractions.

• When the patient become in the active phase of labor, vaginal examination will be repeated every 1-2 hours to know the rate of cervical dilation.

• If patient requests pain relieve, epidural analgesia will be used.

• Fetal heart rate will be recorded every half an hour.

• Labor progress will be plotted on partogram.

Inclusion Criteria:

1. Nulliparous patients.
2. Singleton pregnancy.
3. Living fetus with cephalic presentation.
4. Absence of labor pain.
5. Gestational age 37-42 weeks.
6. No previous uterine surgical procedures.
7. No Liquor abnormalities.
8. Fetal weight less than 4 kilograms.

Exclusion Criteria:

1. Non-vertex presentation.
2. Previous uterine surgery.
3. Multiple pregnancy.
4. Fetal or maternal complications that might cause cesarean section.
5. Liquor abnormalities.
6. Fetal weight more than 4 kilograms.
7. Abnormal umbilical artery Doppler indices or non-stress test.
8. Asthmatic patients or women with allergy to prostaglandins.

200 women all are primigravida between 37-42 weeks gestation to whom induction of labor will be carried out in the casualty of Ain Shams University Maternity Hospital

Raslan et al., 2013 reported accuracy of cervical length or Bishop score was 72% vs 63%. So, proportion of discordant pairs is 0.37. A sample of 200 would achieve a power of 80% to detect statistical significance for an effect size equivalent to odds ratio of 1.9. Two sided McNemar test was used with a confidence level 95%.

All participants and their livebirths were followed for 72 hours following delivery for adverse events