Évaluation de la balance bénéfice/risque selon l’âge gestationnel pour induire la naissance en cas de grossesse prolongée

[Are ultrasound measurements of the cervical length and fetal head-perineum distance predictive of delivery outcome in post-term pregnancies?]

OBJECTIVE

Post-term pregnancy is frequently associated with higher fetal and maternal morbidity and mortality. Its management essentially depends on clinical cervical characteristics as evaluated by the Bishop score (BS). However, BS is poorly predictive of the delivery outcome. We sought to demonstrate that ultrasound measurement of cervical length and evaluation of fetal height could predict the outcome in post-term pregnancies.

METHODS

A prospective single center study was undertaken between the 21st of January and the 1st of June 2013. Fetal height was measured using a transperineal technique and cervical length was evaluated by a vaginal ultrasound on patients consulting and their term date. C-section rates were considered to be the primary judgment criteria.

RESULTS

A total of 136 patients were included. C-section rates in this population was 19%. Fetal height and cervical length were not different between the C-section group and the vaginal delivery group.

CONCLUSION

Our study demonstrates that ultrasound measurement of cervical length and fetal height do not show better results than BS in predicting the outcome of post-term pregnancy. Combining these ultrasound measurements has already been suggested in other studies and promising results have been shown. More studies are necessary to further these results.

To what extent do English language RCT meta-analysis justify induction of low-risk pregnancy for postdates?

Induction for postdates in low-risk pregnancy was adopted with the intent to prevent post-term antepartum stillbirth, the most common cause of perinatal death, based on evidence derived in English language RCT meta-analysis. Systematic English language meta-analysis of RCT studies of induction for postdates in low-risk pregnancy report perinatal mortality rates (PMRs) for low-risk pregnancy ranging from 2.6 to 7.6/1000, based on 2-5 stillbirths among 13-16 perinatal deaths, including diabetic pregnancies as well as other high-risk pregnancies irrelevant to the study question. Baseline PMR≥41 weeks in large international databases for high and low risk pregnancies before routine induction 1998-2003 range from 0.9 to 2.4/1000 or about 300% lower than the reported PMR rates for postdate pregnancies in the expectant management arm in English language RCT meta-analysis. Deaths in the first week far exceed stillbirths in the RCT meta-analysis, the opposite of what is expected. These 2 implausible results bring into question the evidence used to justify induction for postdates≥41 weeks.

The risk factors for failure of labor induction: a cohort study

PURPOSE

To assess how some factors may influence the failure of labor induction.

METHODS

We conducted a prospective observational study from January 2009 to December 2011 with 248 patients who were admitted to the Obstetrics Unit of Ferrara University for labor induction. We selected only patients with unfavorable characteristics such as nulliparity, maternal and gestational age, and Bishop score and specific obstetric conditions such as mild preeclampsia, isolated oligohydramnios, premature rupture membrane, gestational diabetes, and hypertension for the success of labor induction.

RESULTS

The induction was carried out by rapid-release gel dinoprostone. 200 patients (80.6 %) delivered vaginally (Group A), while 48 (19.4 %) underwent a cesarean section (Group B). Maternal age was one independent significant variable (p = 0.01, OR 1.08) determining the risk of cesarean delivery. Patients affected by mild preeclampsia had a three times higher risk for cesarean section. Despite the several unfavorable characteristics of the patients, the cesarean section rate was comparable to that of the normal population.

CONCLUSIONS

Several factors and clinical conditions historically considered as negative predictors of induction result should be reassessed. The success of labor induction is determined by many maternal and fetal variables, which must all be taken into account to avoid unnecessary cesarean sections.

Prolonged and post-term pregnancies: guidelines for clinical practice from the French College of Gynecologists and Obstetricians (CNGOF)

The duration of pregnancy varies between 40(+0) and 41(+3) weeks. Conventionally, and essentially arbitrarily, a pregnancy is considered to be "prolonged" after 41(+0) weeks, but the infant is not considered "post-term" until 42(+0) weeks (Professional consensus). A term birth thus occurs during the period from 37(+0) to 41(+6) weeks. In France, prolonged pregnancies (≥41(+0)weeks) involve 15-20% of pregnant women, and post-term pregnancies (≥42(+0) weeks) approximately 1%. The frequency of post-term pregnancies is very heterogeneous: in Europe and the United States, it ranges from 0.5% to 10% according to country. In prolonged pregnancies, the cesarean section rate-especially the emergency cesarean rate-is multiplied by approximately 1.5 (grade B). From 37(0-6) to 43(0-6) weeks, the risk of perinatal mortality increases regularly, from 0.7‰ to 5.8‰. Meconium aspiration syndrome is responsible for substantial morbidity and mortality, and its incidence increases regularly between 38(+0) and 42(+6) weeks, from 0.24‰ to 1.42‰ (grade B). Similarly, the risks of neonatal acidosis (grade B), 5-min Apgar scores less than 7 (grade B) and admissions to neonatal intensive care (grade B) increase progressively between 38(+0) and 42(+6) weeks. These risks appear to double for post-term growth-restricted newborns (grade C). Ultrasound dating of the pregnancy makes it possible to reduce the risk that it will be incorrectly considered prolonged and that labor will therefore be induced unnecessarily. To harmonize practices, if the crown-rump length (CRL) is correctly measured (this measurement should be taken between 11(+0) and 13(+6) weeks, when CRL should measure from 45 to 84mm), ultrasound dating based on it should be used to determine the official date pregnancy began, regardless of its difference from the date assumed by the patient or estimated based on the date of the last menstrual period. This rule does not apply to pregnancies by IVF, for which the date pregnancy began is defined by the date of oocyte retrieval (Professional consensus). From 37(0-6) to 43(0-6) weeks, the risk of perinatal mortality increases regularly and there is no threshold at which a clear increase in perinatal mortality becomes visible. Fetal monitoring by cardiotocography (CTG) that begins at 41(+0) weeks would cover approximately 20% of women and reduce perinatal morbidity compared with monitoring that begins at 42(+0) weeks (grade C). The frequency recommended for this monitoring ranges between two and three times a week (Professional consensus). For ultrasonography assessment, measurement of the largest fluid pocket is recommended, because measurement of the amniotic fluid index (that is, the sum of the four quadrants) is accompanied by more diagnoses of oligohydramnios, inductions of labor, and cesareans for fetal distress without any improvement in neonatal prognosis (grade A). The practice of assessing the Manning biophysical score increases the number of diagnoses of oligohydramnios and fetal heart rage (FHR) abnormalities and generates an increase in the rates of inductions and cesareans without improving neonatal prognosis. The use of this biophysical score in monitoring prolonged pregnancies is therefore not recommended (grade B). In the absence of a specific disorder, induction of labor can be proposed in patients between 41(+0) and 42(+6) weeks (grade B). Nonetheless, the choice of prolongation beyond above 42(+0) weeks appears to involve an increase in fetal risk, which must be explained to the patient and balanced against the potential disadvantages of induction (Professional consensus). Stripping the membranes can reduce the duration of pregnancy by increasing the number of patients going into labor spontaneously during the week afterward (grade B). Compared to an expectant approach, it does not increase the cesarean section rate (grade A). It reduces recourse to induction by 41% at 41(+0) weeks and by 72% at 42(+0) weeks (grade B), without increasing the risk of either membrane rupture or maternal or neonatal infection (grade B). Used as a tampon or vaginal gel, prostaglandins E2 (PGE2) are an effective method of inducing labor (grade A). They can be used to induce labor successfully, regardless of cervical ripeness (grade A). If misoprostol is chosen, the lowest dose is to be preferred, starting with a vaginal dose of 25μg every 3-6h (grade A). For misoprostol, more powerful studies remain necessary for better defining the doses, routes of administration, tolerance and indications. Misoprostol at any dose is contraindicated in women with uterine scars (grade B). Placement of an intracervical Foley catheter is an effective mechanical means of inducing labor, with less uterine hyperstimulation than prostaglandins and no increase in the cesarean section rate (grade A). Nonetheless, as the risk of infection might be increased, this technique requires more robust evaluation before entering general practice (grade B). In cases of meconium-stained amniotic fluid, pharyngeal aspiration before delivery of the shoulders is not recommended (grade A). The team managing a post-term newborn with meconium-stained amniotic fluid at birth must know how to perform intubation and, if the intubation is not helpful, endotracheal aspiration (grade C) and ventilation with a mask. Routine endotracheal intubation of a vigorous newborn is not recommended (grade A).