Effectiveness of prophylactic carbetocin versus oxytocin following vaginal delivery for preventing severe postpartum hemorrhage.

OBJECTIVE: To compare the effectiveness of prophylactic carbetocin with prophylactic oxytocin for preventing severe postpartum hemorrhage (PPH) following vaginal delivery. METHODS: This before and after cohort study took place between 2020 and 2021 in a university maternity hospital. In 2021, the protocol for PPH prevention immediately after vaginal delivery changed: intravenous oxytocin (5 IU) was replaced by intravenous carbetocin (100 µg). All patients with vaginal births were included, with two groups compared: patients who received prophylactic oxytocin in 2020 and those who received prophylactic carbetocin in 2021. The primary outcome was severe PPH, defined as one or more of the following: estimated blood loss ≥1500 mL, transfusion ≥4 units of red blood cells, Bakri balloon use, embolization, vascular ligation, hysterectomy, and maternal death. RESULTS: Among 4832 women included, 2417 received oxytocin and 2415 received carbetocin. The rate of severe PPH was similar in both groups (0.5% vs. 0.6%, respectively; adjusted odds ratio, 0.8 [95% confidence interval, 0.4-1.8]). The rate of PPH ≥500 mL was lower in the carbetocin group (4% vs. 5.8%; P = 0.004). CONCLUSION: Although prophylactic carbetocin was associated with a reduction in the rate of PPH ≥500 mL, carbetocin is no different to oxytocin in preventing severe PPH caused by atony after vaginal delivery.

Effectiveness of episiotomy to prevent OASIS in nulliparous women at term.

OBJECTIVE: To assess the association between episiotomy and severe obstetric anal sphincter injury (OASIS) in nulliparous women at term according to the use of an instrument for delivery with control confounding by indication. METHODS: This was an observational retrospective cohort study including 12 346 women from 2004 to 2020. All nulliparous women with a cephalic singleton pregnancy were included. The primary outcome was the occurrence of OASIS. Association between episiotomy and OASIS was assessed by multivariate logistic regression with adjustment for confounding factors and stratification on the use of an instrument at delivery. Propensity score matching was used to account for indication bias. RESULTS: Among 12 346 women included, 7803 (63.2%) had an episiotomy and 4543 (36.8%) did not have an episiotomy; the rate of OASIS was similar in both groups (0.7%). After stratification on use of instrument, an association between episiotomy and OASIS was shown in the case of instrumental delivery (odds ratio [OR] 0.46, 95% confidence interval [CI] 0.26-0.80) but not if the delivery was spontaneous (OR 0.76, 95% CI 0.29-1.98). The result was similar after matching on propensity score (in the case of operative vaginal delivery: OR 0.20, 95% CI 0.10-0.75). CONCLUSION: Episiotomy seems to be a protective factor for OASIS in nulliparous woman at term only in the case of operative vaginal delivery.

Classification and evaluation of episiotomy practices from 2004 to 2020 and association with OASIS.

OBJECTIVE: To apply a new classification based on seven clinically relevant subgroups to accurately describe episiotomy practices and evaluate the association between episiotomy and obstetrical anal sphincter injury (OASIS) rates according to the classification's subgroups. METHODS: Observational retrospective cohort study based on a population comprising 39 487 women from January 1, 2004 to December 31, 2020 in a level III university maternity unit. The primary outcome was the overall episiotomy rate in the institution and its trend over time as well as in each subgroup of obstetrical population classification. Secondary outcome was the rate of third- and fourth-degree OASIS, and its association with episiotomy practice. RESULTS: The episiotomy rate decreased significantly from 43.2% to 20% in the total population. The overall OASIS rate was 0.34%; it remained significantly the same during the study period, although the association between OASIS and episiotomy was significant only in group 2 (nulliparous women with instrumental delivery) with a decrease of OASIS rate if using episiotomy (odds ratio 0.5; 95% confidence interval 0.3-0.8). CONCLUSION: The episiotomy rate can be decreased without exposing women to an increased risk of OASIS. This encourages restrictive practice of episiotomy, but episiotomy should be considered in nulliparous women with instrumental delivery.

Cervical ripening for a singleton fetus in breech prensentation at term: Comparison between mechanical and pharmaceutical methods.

Although various international professional societies currently recommend trial of vaginal delivery of term fetuses in breech presentation, the question of the method of cervical ripening, when necessary, remains open. OBJECTIVE: To compare the effectiveness of two methods of cervical ripening for delivery of a singleton fetus in breech presentation at term: a mechanical method (balloon catheter) and a pharmaceutical method (prostaglandins). STUDY DESIGN: This two-center retrospective study reviewed records from 2014 through 2019 in two French maternity units with two different cervical ripening methods for fetuses in breech presentation. The study included all women with cervical ripening for a medical indication with a live singleton fetus in breech presentation ≥ 37 weeks, with an unfavorable cervix. The group treated with a mechanical method was compared with the group receiving a pharmaceutical method. The cesarean delivery rate was the principal outcome, and maternal and neonatal morbidity the secondary outcomes. RESULTS: We included 74 women, 19 with mechanical cervical ripening, and 55 with pharmaceutical treatment. The cesarean rate was 57.9% in the balloon catheter group and 40% in the prostaglandin group (P = 0.097) (crude OR =2.06, 95% CI [0.72 - 5.94]; adjusted OR = 2.88, 95% confidence interval [0.52-15.96]), and the postpartum hemorrhage rates 21.1% and 1.8% respectively (P = 0.008). Neonatal morbidity did not differ significantly. CONCLUSION: Although the cesarean rate and neonatal morbidity and mortality did not differ significantly between these two methods of cervical ripening, our study lacked power.

Impact of precipitous labor on the onset of transient tachypnea in vaginal deliveries at term.

OBJECTIVE: The objective of the present research was to study the association between precipitous labor (less than 3 h) and the onset of transient tachypnea in singleton fetuses in cephalic presentation with term vaginal deliveries. METHODS: This cohort study included women delivered from 2013 through 2017 in our French tertiary university hospital maternity unit. Inclusion criteria were vaginal delivery of liveborn singleton fetus in cephalic presentation and at term. We compared women with precipitous labor and those with longer labor. The principal endpoint was the rate of transient tachypnea of the newborn (TTN). We investigated risk factors for TTN besides duration of labor. RESULTS: Comparison of 2644 women with precipitous labor and 7571 with longer labor showed a lower TTN rate in the precipitous labor group (1.6 vs 2.7%; P = 0.003). The association was no longer significant after adjustment for the risk factors identified in the univariate analysis (adjusted OR 0.99, 95% CI 0.64-1.54). Risk factors identified for TTN were non-clear amniotic fluid, shoulder dystocia, umbilical cord encirclement, birth weight less than 2500 g, use of cervical ripening and operative vaginal delivery. CONCLUSION: Precipitous labor, lasting less than 3 h, is not associated with a higher risk of transient tachypnea in term newborns after vaginal delivery.

Perinatal mortality and morbidity, timing and route of delivery in monoamniotic twin pregnancies: a retrospective cohort study.

PURPOSE: Monoamniotic twin pregnancies are at high risk of perinatal complications and fetal loss. The objective of this study is to describe the management and outcomes of monoamniotic twin pregnancies in a French university obstetrics department. METHODS: Retrospective review of all consecutive monoamniotic twin pregnancies managed between 1992 and 2018 in a level-3 university hospital maternity unit. Antenatal variables, gestational age and other neonatal characteristics at delivery, mode of delivery, and its reason were recorded, together with outcomes, including a composite adverse neonatal outcome. RESULTS: Overall, 46 monoamniotic twin pregnancies (92 fetuses) were identified during the study period. Among them, 27 fetal losses and 2 early neonatal deaths were reported. Congenital abnormalities accounted for 33.3% of the 27 fetal losses, and unexpected fetal deaths for 29.6%. Among the 37 women who gave birth to 65 live infants at 23 or more weeks of gestation, 17 had cesarean and 19 vaginal deliveries. Overall and composite adverse neonatal outcomes did not differ significantly for the 33 children born vaginally and the 31 by cesarean deliveries. The prospective risk of intrauterine death in all 92 fetuses reached its nadir of 1.8% at 336/7 weeks. CONCLUSION: This series confirms the still high risk of fetal and neonatal death of these twins and shows that congenital abnormalities but also unexpected fetal deaths account for the majority of pre- and postnatal mortality. Our data suggest that vaginal delivery of monoamniotic twins is safe and that delivery for uncomplicated monoamniotic twins should be considered around 33 weeks of gestation, but not later than 35 weeks.

Use of the Robson classification to understand the increased risk of cesarean section in case of maternal obesity.

BACKGROUND: The aim of this study was to identify characteristics of pregnant women with obesity that contribute to increased cesarean rate. METHODS: Retrospective cohort in a single academic institution between 2012 and 2019. Women who delivered during this period were classified according to the Robson classification. Women with normal body mass index (N = 11,797) and with obesity (N = 2991) were compared. The contribution of each Robson group to the overall caesarean rate were compared. RESULTS: The overall cesarean rate was higher for women with (28.1%) than without (14.2%, p < 0.001) obesity. This result came mainly from Robson group 5a (history of one cesarean). After adjustment for medical factors within this group, the association between maternal obesity and cesarean during labor was significant. CONCLUSIONS: The higher cesarean rate in women with obesity is explained by Robson group 5a in which obesity is an independent risk factor of in labor cesarean delivery.

Double-balloon catheter versus prostaglandin for cervical ripening to induce labor after previous cesarean delivery.

PURPOSE: To compare the effectiveness of cervical ripening by a mechanical method (double-balloon catheter) and a pharmacological method (prostaglandins) in women with one previous cesarean delivery, an unfavorable cervix (Bishop score < 6), and a singleton fetus in cephalic presentation. METHODS: This retrospective study, reviewing the relevant records for the years 2013 through 2017, took place in two French university hospital maternity units. This study included women with one previous cesarean delivery, a liveborn singleton fetus in cephalic presentation, and intact membranes, for whom cervical ripening, with unfavorable cervix (Bishop score < 6) was indicated for medical reasons. It compared two groups: (1) women giving birth in a hospital that uses a protocol for mechanical cervical ripening by a double-balloon catheter (DBC), and (2) women giving birth in a hospital that performed pharmacological cervical ripening by prostaglandins. The principal endpoint was the cesarean delivery rate. The secondary outcome measures were maternal and neonatal outcomes. RESULTS: We compared 127 women with prostaglandin ripening to 117 women with DBC. There was no significant difference between the two groups for the cesarean rate (42.5% in the prostaglandin group and 42.7% in the DBC group; p = 0.973; crude OR 1.01 [0.61-1.68]; adjusted OR 1.55 [0.71-3.37]). The median interval between the start of ripening and delivery did not differ between the groups (28.7 h in the prostaglandin group vs 25.6 h in the DBC group; p = 0.880). Neonatal outcomes did not differ between the groups, either. There was one case of uterine rupture in the prostaglandin group, with no associated maternal or neonatal morbidity. There were no neonatal deaths. The postpartum hemorrhage rate was significantly higher in the DBC group. CONCLUSION: For cervical ripening for women with one previous cesarean, the choice of a pharmacological or mechanical protocol does not appear to modify the mode of delivery or maternal or neonatal morbidity.

Term spontaneous trial of labor in nulliparous women of short stature: A hospitals-based cohort study.

OBJECTIVES: To study the mode of delivery in a well selected cohort of short nulliparous women. STUDY DESIGN: Hospitals-based cohort study between 2010-2018. The threshold (150 cm, i.e 2,3°p), for the short stature was chosen before the analysis by corresponding to - 2SD of the average population size distribution of all women who delivered over the same period: 2010-2018. Were included nulliparous women with a heigh ≤ 150 cm in term spontaneous labor with a single livung fetus in vertex presentation without malformation. Exclusion criteria were: multiparous, scarred uterus, twin pregnancy, induced labor, preterm delivery (< 37 W P), non-vertex pregnancy, medical termination of pregnancy, stillbirth, severe fetal malformations, pre-labor cesarean, and late dating ultrasound. The main outcome was the mode of delivery. Univariate and multivariate analysis adjusted on potential confounding variable were performed to investigate the risk of intrapartum CS. RESULTS: 178 nulliparous women were included. The mean height was 148 cm. The rate of spontaneous vaginal delivery, operative vaginal delivery a nd intrapartum CS were :35,4 %, 35,4 % and 29,2 % respectively. Intrapartum CS was performed during the first stage labor in 15 (28, 8 %) women and during the second stage in 37 (71, 2 %) women. An arrest of labor was significantly more frequent in the active labor than the early labor stage: 62,1 % vs. 33.3 % (p = 0, 02). In univarate analysis were associated with intrapartum CS : Gestational diabetes, birthweight> 3,5 kg, individual adjusted birthweight >90°p, occiput posterior, oxytocin use, cephalic circumference. After adjustment on birthplace and overweight (BMI over 25), only a birthweight > 3,5 kg remains associated with the risk of intrapartum CS (aOR4.3 ;95 %CI 1.96-10.2). CONCLUSION: An attempt of vaginal birth is a reasonable option for short stature women. Maternal height could be included in the selection criteria for planned birth center or home birth. The customized gestational-related optimal weigh could be useful to identify large of gestational age fetus.

Trial of labor after cesarean and contribution of pelvimetry in the prognosis of neonatal morbidity.

INTRODUCTION: To estimate the association between an abnormal pelvic dimension at pelvimetry and the occurrence of severe neonatal morbidity after trial of labor after cesarean (TOLAC). MATERIALS AND METHODS: Retrospective observational cases-controls study conducted at a level 3 maternity units between 2006 and 2016. Included women were patient with trial of labor after one previous cesarean section, alive singleton fetus in cephalic presentation ≥ 37WG. Two groups were compared according to pelvic mesures at pelvimetry: pelvic dimension considered as abnormal, defined by Conjugate Diameter <10.5cm and/or Transverse Diameter <12cm and pelvic dimension considered as normal for other women. The primary outcome was a composite criterion of neonatal morbidity and mortality. A logistic multivariate regression model was use to estimate the association between an abnormal pelvic dimension at pelvimetry and the occurrence of severe neonatal morbidity. RESULTS: 2474 women were included. 863 (34.8 %) have a normal pelvic dimension and 1611 (65.2 %) an abnormal. Characteristics of labor were similar in two groups. Success of TOLAC was 84.7 % in normal pelvic group and 64.6 % in abnormal dimension of pelvic group. Neonatal morbidity was similar between two groups (1.7 % in normal pelvic dimension group versus 2.3 % in abnormal pelvic dimension group, p=0.26; crude OR: 1.39 (0.77-2.49) ; adjusted OR : 0.93 (0.51-1.68)). DISCUSSION: There were no association between pelvic dimension at pelvimetry and neonatal morbidity. In case of abnormal pelvic dimension, a combination of more prudence, and stringent user practices, achieve a high rate of vaginal delivery and a neonatal morbidity comparable to the normal pelvic dimension group.

Long interpregnancy interval and mode of delivery.

PURPOSE: WHO sets 24 months as the ideal minimum interpregnancy interval (IPI) to minimize maternal and perinatal adverse outcomes. Some studies suggest that an interval longer than 59 months may affect these outcomes, but little is known about its influence on labor. The primary objective of this study was to compare the cesarean delivery rate between primiparous women with a long IPI and, on the one hand, primiparous women with an ideal minimum IPI of 18-24 months and, on the other hand, with nulliparous women. METHODS: This retrospective cohort study of 17 years included nulliparas and primiparas who gave birth to live singleton fetuses in cephalic presentation after 22 weeks of gestation. Women with an IPI < 18 months or from 24 to 59 months were excluded, as were women with planned cesarean. We analyzed three groups: primiparous women with a long IPI defined as > 59 months, primiparous women with an ideal minimum IPI (18-24 months), and nulliparous women. RESULTS: The study included 18,503 women: 1342 women in the "long IPI" group, 1388 in the "ideal minimum IPI" group, and 15,773 in the nulliparous women group. The cesarean delivery rate was significantly higher in the long compared to the ideal minimum IPI group [12.2% vs. 6.3%, respectively; aOR = 2.2 (95% CI 1.6-3.1)], but both groups had similar durations of labor, regardless of mode of delivery. Women in the long IPI group had significantly lower cesarean rates than nulliparous women [12.2% and 14.3%, respectively; aOR = 0.5 (95% CI 0.4-0.7)], and the nulliparous women had a significantly longer mean duration of labor. CONCLUSIONS: Primiparas with a long IPI, compared with ideal minimal IPI have a higher risk of cesarean delivery during labor. Compared with nulliparous women, primiparous women with a long IPI had a lower cesarean rate.

Ontogeny of cytokine responses to PHA from birth to adulthood.

BACKGROUND: Altered production of cytokines is believed to contribute to early childhood susceptibility to infection. The aim of this study was to get further insight into the developmental patterns of cytokine responses from birth to adulthood. METHODS: The expression levels of 13 cytokines were compared in the supernatants of phytohemaggluttinin (PHA)-stimulated whole blood from healthy neonates (cord blood, n = 8), infants ( < 1-year-old, n = 20), and school-aged children (3-15 y; n = 20). Five adults were used as reference. RESULTS: While Th1, Th2, and Th17 cytokine levels increased progressively from birth to childhood (Mann-Whitney, p < 0.003), high IL-10 secretion at birth dropped to low adult levels in infants (p < 0.004) such that a negative correlation between IL-10 and Th1, Th2, and Th17 cytokine levels at birth (Spearman's correlation, r < -0.70, p < 0.01) converted to a positive correlation in infants (r > 0.60, p < 0.001). Finally, high IL-2, IL-7, and Granulocyte-Colony Stimulating factor (G-CSF) cytokine levels at birth decreased steadily over the first year of life (Mann-Whitney, p ≤ 0.001). CONCLUSION: The most noticeable result of the study is the rapid shift from enhanced IL-10 secretion capacity at birth toward balanced IL-10/Th1/Th2/Th17 cytokine levels early in life. This change appears an essential precondition to fight pathogens and at the same time to avoid overwhelming inflammatory reactions.

Impact of maternal age on intrapartum caesarean delivery rate in nulliparas with spontaneous labour.

BACKGROUND: The advanced maternal age rate increases in developed countries. Older women have more pre-existing condition than youngest women and develop more frequently obstetrical pathologies responsible for a higher rate of caesarean delivery before labour and labour induction. For aged nulliparous without pathology who experience spontaneous labour, there is few data on the mode of delivery and on physiological labour according to maternal age. OBJECTIVE: To compare the intrapartum caesarean delivery rate according to maternal age, for nulliparous with planned vaginal delivery and spontaneous labour at term. METHODS: Retrospective cohort in a single academic institution between January 2000 and June 2017. All nulliparous women with planned vaginal delivery with live singleton in cephalic presentation at and after 37 weeks of gestation with spontaneous labour were included (n = 10,611). Two groups were compared: nulliparous women aged 20-34 and nulliparous women aged 35 and over. The main outcome was the intrapartum caesarean delivery rate. A subgroup analysis was performed for nulliparous with more advanced maternal age defined as women over 40. RESULTS: Among the 10,611 women included in this analysis, 8,993 (84.8%) were aged 20-34 and 1,618 (15.2%) were aged over 35. From the latter 367 (22.7%) were over 40 years old. The intrapartum caesarean delivery rate was similar between women aged between 20 and 34 and women aged over 35 (10.8% compared to 8.8%; cOR 0.91, 95% CI 0.76-1.08; aOR 0.91, 95% CI 0.76-1.09). The indications of caesarean were similar in both groups. No differences were found between both groups for mean labour duration (430.9 min for the [20-34] years group compared to 428.0 min for the over 35 years group, p = 0.654). The subgroup analysis performed on nulliparous with more advanced maternal age yielded similar results. CONCLUSION: For nulliparous at term in spontaneous labour, an advanced maternal age was not associated with an increased intrapartum caesarean delivery rate.

[Pulmonary glial heterotopia: Unique lesion in an infant with anencephalic twin]. / Hétérotopie gliale pulmonaire : une lésion exceptionnelle chez un nourrisson avec un jumeau anencéphale.

Pulmonary glial heterotopia is an extremely rare entity whose pathophysiology remains unclear. We report for the first time one case of pulmonary glial heterotopia occured in a one-month baby free from any malformation. She has the particularity of being born from monozygotic monochorionic twin pregnancy where her anencephalic exencephalic sister suffered a medical termination of pregnancy. She presented neonatal respiratory distress, which recurred one month later. Chest X-ray revealed bilateral cystic pulmonary lesions mainly located in the right lung. Given the suspicion of congenital cystic adenomatoid malformation (CCAM), she underwent an upper and a lower right lung lobectomy at four months old. The pathological study found a multi-cystic lesion consisted of well-differentiated and poorly cellular glial tissue sometimes lined by bronchic epithelium. There was no pathological evidence for a CCAM. The evolution was favorable after surgery with an infant who was well five months later. This is one of the very few cases where the disease did not lead to rapid death in utero or during the perinatal period. This suggests that effective management by surgery could be a decisive factor in the survival of these patients.

Associated factors of umbilical cord blood collection quality.

After 30 years of hematopoietic stem cell use for various indications, umbilical cord blood is considered as an established source of cells with marrow and postmobilization peripheral blood. The limited number of cells still remains a problematic element restricting their use, especially in adults who require to be grafted with a higher cell number. Improving the quality of harvested cord blood, at least in terms of volume and amount of cells, is essential to decrease the number of discarded units. In this review, we examine several variables related to parturient, pregnancy, labor, delivery, collection, the newborn, umbilical cord, and placenta. We aim to understand the biologic mechanisms that can impact cord blood quality. This knowledge will ultimately allow targeting donors, which could provide a rich graft and improve the efficiency of the collection.

Posterior urethral valves and vesicoureteral reflux: can prenatal ultrasonography distinguish between these two conditions in male fetuses?

OBJECTIVE: The objective of the study was to evaluate prenatal sonographic signs that distinguish male fetuses with posterior urethral valves (PUV) from those with vesicoureteral reflux (VUR). METHODS: Prenatal data were retrospectively retrieved from all consecutive women delivering between 2003 and 2012 of a male newborn with a postnatal diagnosis of PUV or VUR. Prenatal parameters included fetal bladder characteristics, identification of a dilated posterior urethra, and change in shape and size in the fetal renal pelvis or ureter. RESULTS: One hundred thirty-six women gave birth to a male newborn with a postnatal diagnosis of PUV (n = 49) or VUR (n = 87). The presence of posterior urethral dilatation [21 (42.9%) fetuses versus 0 (0%), p = 0.000], a thickened fetal bladder wall [37 (75.5%) vs 4 (4.6%), p = 0.000], and anhydramnios [14 (28.6%) vs 0, p = 0.000] were strongly associated with the postnatal diagnosis of PUV. Change in shape and size in the fetal renal pelvis or ureter was observed in 15 (17.2%) of 87 children with VUR versus 1 (2.0%) out of 49 with PUV (p = 0.010). CONCLUSIONS: Prenatal ultrasound may differentiate with reasonable accuracy male fetuses with a postnatal diagnosis of PUV from those with VUR. © 2016 John Wiley & Sons, Ltd.

Insulin treatment of maternal diabetes mellitus and respiratory outcome in late-preterm and term singletons.

OBJECTIVES: While the incidence of diabetes mellitus (DM) during pregnancy has been steadily increasing in recent years, the link between gestational DM and respiratory outcome in neonates has not been definitely established. We asked the question whether DM status and its treatment during pregnancy could influence the risk of neonatal respiratory distress. DESIGN: We studied in a large retrospective cohort the relationship between maternal DM status (non-DM, insulin-treated DM (IT-DM) and non-insulin-treated DM (NIT-DM)), and respiratory distress in term and near-term inborn singletons. RESULTS: Among 18,095 singletons delivered at 34 weeks of gestation or later, 412 (2.3%) were admitted to the neonatal intensive care unit (NICU) for respiratory distress within the first hours of life. The incidence of NICU admission due to respiratory distress groups was 2.2%, 5.7% and 2.1% in the non-DM, IT-DM and NIT-DM groups, respectively. Insulin treatment of DM, together with several other perinatal factors, was associated with a significant increased risk for respiratory distress. Several markers of the severity of respiratory illness, including durations of mechanical ventilation and supplemental oxygen, and hypertrophic cardiomyopathy were also found increased following IT-DM as compared with NIT-DM. In a multivariate model, we found that IT-DM, but not NIT-DM, was significantly associated with respiratory distress independent of gestational age and caesarean section, with an incidence rate ratio of 1.44 (1.00-2.08). CONCLUSIONS: This study shows that the treatment of maternal DM with insulin during pregnancy is an independent risk factor for respiratory distress in term and near-term newborns.

Identification of women at high risk for severe perineal lacerations.

OBJECTIVES: To evaluate the frequency and to identify the risk factors of severe perineal lacerations and the subgroup of women exposed to the highest risk for these complications. STUDY DESIGN: We conducted a case-control study in a large cohort of women for which vaginal delivery management consisted in systematic perineal support and restrictive use of mediolateral episiotomy. The case group comprised women with severe perineal lacerations while the control group comprised women without severe perineal lacerations. Maternal, labor, delivery and neonatal characteristics were analyzed in logistic regression models and a classification and regression tree (CART) was constructed. RESULTS: Between 2000 and 2009, 19,442 women delivered vaginally in our centre, 88 of whom had severe perineal lacerations (0.5%). Instrumental delivery (aOR 4.17, 95% CI 2.51-6.90), nulliparity (aOR 2.58, 95% CI 1.55-4.29), persistent posterior orientation (aOR 2.24, 95% CI 1.02-4.94) and increased birth weight (aOR 1.28, 95% CI 1.03-1.60) were independent risk factors of severe perineal lacerations whereas mediolateral episiotomy had a protective effect (aOR 0.38, 95% CI 0.23-0.63). CART identified instrumental delivery of neonates smaller than 4500 g in persistent posterior orientation in nullipara without mediolateral episiotomy as the clinical situation associated with the highest risk of severe perineal lacerations (12.5%). Conversely, patients with the lowest risk (0.1%) were those delivering spontaneously, neonates larger than 3200 g after mediolateral episiotomy. CONCLUSIONS: Instrumental delivery, nulliparity, persistent posterior orientation and increased birth weight are independently associated with severe perineal lacerations. Restrictive use of mediolateral episiotomy protects against severe perineal lacerations especially in case of instrumental delivery.