Simonson, Colin MD; Barlow, Patricia MD; Dehennin, Nathalie MD; Sphel, Marianne MD; Toppet, Véronique MD; Murillo, Daniel MD; Rozenberg, Serge MD
Vacuum extraction is an instrument of choice when the shortening of the second stage of labor is necessary.1,2 It has been preferred to forceps by some practitioners because of the low incidence of maternal trauma and the ease of its use.1,3,4 However, the incidence of neonatal complications remains a matter of concern as evidenced by recent publications on the subject.4–7 The most common complications, such as caput succedaneum, scalp bruising, cephalhematoma, and retinal hemorrhage have a good prognosis.8–10 Serious neonatal complications, such as subgaleal hemorrhage and intracranial hemorrhage, have a worse prognosis 10–15. Although vacuum extraction seems to be associated with a higher risk of complications, when compared with spontaneous vaginal birth, one should note that the prevalence of these complications varies considerably in the literature, ranging between 4% and 26% for cephalhematoma,1,8,16–19 between 0% and 21% for subgaleal hemorrhage,8,13,17,18,20,21 and between 0.11% and 0.34% for intracranial hemorrhage.1,8,14,15,22
As part of a protocol, newborns who were delivered by vacuum extraction at the Centre Hospitalier Universitaire St. Pierre systematically underwent transfontanellar ultrasound and skull X-ray postpartum. The purpose of this study was to estimate the rate of neonatal complications in a cohort of vacuum-assisted deliveries, identify risk factors associated with the occurrence of these complications, and evaluate the usefulness of skull radiography and transfontanellar ultrasound after vacuum extraction.
MATERIALS AND METHODS
We reviewed the charts of a cohort of 1,123 attempted, vacuum-assisted, singleton deliveries performed at the Centre Hospitalier Universitaire St. Pierre, a university community hospital in downtown Brussels, between January 2000 and December 2004. This represents 10% of all deliveries (N=11,405) during that period. All successful vacuum-assisted deliveries of a singleton at a gestational age of 37 or more completed weeks were included in the study (n=913). We analyzed separately premature babies (less than 37weeks) because they are at higher risk of complications (n=24). Similarly, failed cases of vacuum extraction followed by a caesarean delivery were also analyzed separately (n=36). Cases for which X-ray and ultrasonographic protocols were missing (n=150) and multiple pregnancies (n=18) were excluded from the analysis.
Vacuum extractions were performed only at full cervical dilatation, with the fetal head at station +1 or lower. Indications for vacuum extraction were principally an absence of progression of the second stage of labor or a malposition of the vertex, fetal distress, or a maternal indication such as exhaustion. Multiple indications were often recorded. Three consecutive tractions without progression, two dislodgments of the cup, or failure to deliver the baby in eight tractions were considered as indications for an immediate caesarean delivery. As part of the protocol, a pediatrician was present at the delivery whenever a vacuum extraction was attempted. The obstetric data were recorded immediately after delivery on a computerized chart. Each newborn was evaluated at birth by a pediatrician, and all infants underwent transfontanellar ultrasonography and skull X-ray during the postpartum. These were all performed and interpreted by the same experienced pediatric radiologist.
Maternal and infant data were taken from the obstetric and neonatal files. Cephalhematoma, scalp edema, and skull fracture were diagnosed using a two-incidence skull X-ray, whereas intracranial hemorrhage was diagnosed using transfontanellar ultrasound. An admission in the neonatal intensive care clinic (NICU), a cord pH less than 7.20, and a low Apgar score at 1 or 5 minutes were considered to be adverse neonatal features.
Descriptive statistics were used (frequency, mean or median, and range were used for continuous data and categorical or nonnormally distributed data, respectively). Differences in frequencies between groups were compared using χ2 (P=.05). Relative risks and 95% confidence intervals were calculated for risk factors. For exploratory purposes, we also analyzed subgroups even though no differences had been found between groups.
Multiple logistic regression was further carried out, using as dependent variable the presence of any of the following events: cranial fractures, cephalhematomas, scalp edema, intracranial hemorrhage. Covariates were maternal age (younger than 20 years, between 20 and 35 years, more than 35 years), parity (nulliparity compared with multiparity), the station of fetal head (mid, low, and outlet station), the number of tractions (one, two, three, or more than three), and the dislodgments of the cup (yes or no). The model was selected using a forward stepwise procedure; a significance probability of less than 5% was required to enter a covariate in the model. All reported P values are two-tailed. We also constructed receiver operator curve to assess the accuracy of this model. This study was reviewed and approved by the institutional review board.
X-ray and ultrasonographic protocols were missing in 150 cases. Vacuum extraction was applied to 24 premature neonates (less than 37weeks), and in 36 cases vacuum extraction failed and was followed by a cesarean delivery. These two groups were analyzed separately. Finally, of 1,123 attempts, 913 full-term newborns successfully delivered using a vacuum extractor were assessed. The mean maternal age of this cohort was 29±6 years (range 15–45 years). Six hundred eighty-nine women were nulliparous, (75.47%; 95% confidence interval [CI] 72.62–78.31). The mean estimated gestational age was 40±1 weeks (range 37–42 weeks). Protracted second stage of labor (57.94%; 95% CI 54.67–61.21) and fetal distress (46.77%; 95% CI 43.47–50.07) were the most frequent indications for intervening.
The main maternal and obstetric characteristics of the group studied are presented in Tables 1 and 2. A summary of the fetal morbidity encountered in the 913 successful vacuum extractions of full term newborns is presented in Table 3. Two hundred thirty-five newborns (25.74%; 95% CI 22.85–28.63) were admitted to the NICU. Indication of admission in the NICU included fetal distress (n=77; 32.77%; 95% CI 26.64–38.89), antibiotherapy (n=112; 47.66%; 95% CI 41.14–54.18), hyperbilirubinemia (n=17; 7.23%; 95% CI 3.85–10.61), grunting (n=12; 5.10%; 95% CI 2.23–7.98), respiratory distress (n=8; 3.40%; 95% CI 1.04–5.77), maternal indication (n=5; 2.13%; 95% CI 0.24–4.01), and other (n=10; 4.25%; 95% CI 1.62–6.89). Scalp edema, cephalhematoma, and skull fracture were assessed by cranial radiography and were diagnosed in 18.73% (95% CI 16.15–21.31), 10.84% (95% CI 8.79–12.90), and 5.03% (95% CI 3.59–6.49) of cases, respectively. Intracranial hemorrhage was detected in eight cases (0.87%; 95% CI 0.26–1.49). Screening by transfontanellar ultrasonography identified seven of these as three subependymal hemorrhages and four plexus choroideus hemorrhages. The clinical status of these seven newborns was reassuring and only one of them required admission to the NICU for a brachial plexus palsy. For the eighth case, intracranial hemorrhage was discovered in a newborn who developed severe anemia and signs of irritability in the postpartum period. Transfontanellar ultrasonography had revealed no pathologic findings, but this newborn underwent a computed tomography (CT) scan, which elicited a subdural and a subarachnoidal hemorrhage in the area of the tentorium. He was admitted to the NICU and recovered completely after 4 days of conservative treatment. This child showed no fetal distress during labor, underwent a low-station vacuum extraction because of protracted second stage, and was extracted in six pulls without any pop-up. His Apgar scores were 3 and 8 at 1 and 5 minutes, respectively, and his pH was 7.33. There were no cases of subgaleal hemorrhage in the studied group.
The incidence of cranial fracture was higher in newborns from nulliparous mothers (6.58%) than in the multiparous group (2.35%; relative risk [RR] 2.79; 95% CI 1.12–6.96; P=.02). Nulliparity was also associated with a high incidence (20.49%) of low 1-minute Apgar score (less than 7) (RR 1.42; 95% CI 1.00–2.02; P=.045). No correlation between parity and other complications was found.
We found no relationship between maternal age and neonatal complications. For exploratory purposes, we further investigated nulliparous and multiparous women to test whether maternal age had an influence on neonatal outcome. In the nulliparous group, no relation between maternal age and neonatal complications was found. Among multipara, older age (older than 35 years) was associated with an increased incidence of cranial fractures. We found an incidence of 7.94% of fractures in this age group of multiparous women, compared with no fracture among younger multiparous women (younger than 35 years; P=.001). Multipara older than 35 years of age delivered newborns with a low cord pH (less than 7.20), ie, in 37.20% of cases, which represents a three-fold risk increase (RR 2.97; 95% CI 1.48–5.98) when compared with younger multipara. (P=.001).
We found no relation between the frequency of complications and fetal sex, birth weight, or cranial circumference. Although intracranial hemorrhage was found in 2.75% of the newborns with a birth weight more then 4,000 g compared with 0.67% of babies with a birth weight less than 4,000 g, this difference was not statistically significant (P=0. 08).
We found no relation between gestational age and neonatal complications. Vacuum applications at mid or low station were associated with a higher incidence of cephalhematoma (13.11% and 13.56%) when compared with vacuum applied at the outlet (6.81%; RR 1.92; 95% CI 0.85–4.32; RR 1.99; 95% CI 1.17–3.38; P=.03). When compared with vacuum extraction at the outlet, application at middle or low station was associated with a higher risk of low 1-minute Apgar scores, 30.43% (RR 2.38; 95% CI 1.46–3.89; P≤.05) and 20.37% (RR 1.53; 95% CI 1.05–2.21; P≤.05). Application at middle station was associated with a higher risk of low 5-minute Apgar scores, 13.04% (RR 3.83; 95% CI 1.54–9.55;P≤.05). More admissions to the NICU were also observed when extractions were performed at middle or low station: 60.87% (RR 1.88; 95% CI 1.28–2.76; P≤.0.05) and 35.55% (RR 3.54; 95% CI 2.75–4.56; P≤.05). An extraction after more than three tractions was associated with low 1- and 5-minute Apgar scores, 36.44% (RR 3.49; 95% CI 2.21–5.52; P<.001) and 11.01% (RR 10.03; 95% CI 2.41–41.69;P≤.05), entailing more admissions to the NICU, 39.66% (RR 2.33; 95% CI 1.63–3.33; P≤.05). One hundred sixty-seven dislodgments of the cup occurred in the group of 913 deliveries. In sixteen cases (9.58%) a cranial fracture was revealed by skull X-ray. This was twice as many as in newborns who were delivered without dislodgment of the cup (RR 2.11; 95% CI 1.18–3.76; P=.011). Dislodgement of the cup was also associated with an increased incidence of cephalhematoma (18.56%; RR 1.86; 95% CI 1.26–2.75; P=.002). The risk of scalp edema (26.34%; RR 1.41; 95% CI 1.05–1.91; P=.03), low 1-minute Apgar score (27.68%; RR 1.63; 95% CI 1.23–2.18; P=.001), low 5-minute Apgar score (7.91%; RR 2.07; 95% CI 1.11–3.84; P=.02), and admission to the NICU (34.46%; RR 1.45; 95% CI 1.14–1.85; P=.003) were also significantly higher when dislodgement had occurred. None of the eight intracranial hemorrhages followed such event.
Disjunction or overlapping of the suture line was associated with higher incidences of scalp edema (RR 1.91; 95% CI 13.35–2.72; P=.003) and of admission to NICU (RR 1.60; 95% CI 1.14–2.26; P=.008), but without any effect on other complications, such as cephalhematoma, fracture, or intracranial hemorrhage. When vacuum was applied for fetal distress, higher incidences of low 1-minute Apgar scores (RR 2; 95% CI 1.51–2.64; P<.001) and low cord pH (RR 2.14; 95% CI 1.52–3.02; P<.001) were observed, and newborns were admitted to the NICU more frequently (RR 1.27; 95% CI 1.02–1.59; P<.05).
Cephalhematoma was associated with a higher incidence of cranial fracture (10.10%; RR 2.05; 95% CI 1.05–4.00; P=.034) but it was not predictive for intracranial injury.
Using multiple regression analyses, the presence of dislodgments (P<.05) and nulliparity (P<.06) were associated with skull fracture; maternal age (P<.05) was included in a model for scalp edema, and dislodgments of the cup (P<.01) and the level of application of the vacuum (P<.05) was included in a model of cephalhematoma. Nulliparity (P<.01), the presence of dislodgments, a high level of application of the extractor, and a high fetal weight (P<.05) were associated with the presence of any the following events: fracture skull, scalp edema, cephalhematoma, and intracranial hemorrhage. These covariates were accepted in the model predicting any of these events. Still, the selected model had a poor discriminant value as illustrated by the area under the receiver operator curve (Fig. 1).
Cesarean delivery was performed in 36 cases, after an attempted vacuum extraction. The maternal and obstetric characteristics of this group are presented in Tables 4 and 5. Four scalp edema (12.90%), seven cranial fractures (22.58%), two cephalhematoma (6.7%), and one hemorrhage (2.78%) were diagnosed in this group. Nineteen newborns were admitted to the NICU (52.78%).
A girl (38.6 weeks) was delivered by cesarean delivery after a vacuum attempt at low station on an asynclitic head in occiput posterior presentation and episodes of cup dislodgement. She had an Apgar score of 2 and 5 at 1 and 5 minutes. She was cyanotic and presented bradycardia and neurologic anomalies (hypotonicity, ocular deviation, and anisocoria). A CT scan and magnetic resonance imaging revealed a subdural and subarachnoidal hemorrhage. The neonate was transferred to another children’s hospital in anticipation of performing neurosurgery. Intracranial hemorrhage was also observed using transfontanellar ultrasonography. She completely recovered spontaneously, and disappearance of the blood collection was confirmed by ultrasonography at 20 days after birth.
Twenty-four premature newborns were extracted by vacuum. Maternal characteristics of this group are presented in Table 6. The mean gestational age was 35 weeks (range 29–36 weeks). Table 7 presents other obstetric characteristics from this group. The mean birth weight was 2,640 g (range 1,190–3,830 g). Sixty-two percent of those infants were admitted in the NICU. Among this group, 14.29% showed a scalp edema, 21.43% a bone fracture, and 21.43% a cephalhematoma. There were no hemorrhages.
One neonate (36 weeks) suffering from severe fetal distress at admission was delivered after one traction but died on day 5. Its intracranial ultrasonography showed a diffuse hyperechogenicity suggesting generalized cerebral edema, but without signs of hemorrhage.
Intracranial and subgaleal hemorrhage are considered to be the most serious neonatal complications of vacuum extraction because both may threaten the newborn’s life.23 Early recognition and prompt management of these conditions reduce the neonatal mortality and morbidity rate.10
Subgaleal hematoma is characterized by an accumulation of blood in the subaponeurotic space, beneath the epicranial aponeuroses of the scalp and the periosteum. This condition is dangerous because of the large potential space for blood accumulation and the possibility of life-threatening hemorrhage.23,24 Several authors reported a strong association between subgaleal hematoma and vacuum extraction, entailing a high mortality rate (2.7–22.8%).11,13,24 Intracranial hemorrhage may occur in the subdural, subarachnoidal, intraparenchymal, and intraventricular spaces. Subdural hemorrhage is almost always the result of a birth trauma.13 Other types of intracranial hemorrhage have a more complex cause, which in addition to mechanical trauma may include birth asphyxia, prematurity, hemorrhagic diathesis, infection, and vascular abnormalities.10 A large, population-based, retrospective study reported higher rates of intracranial hemorrhage among infants delivered by instrumental extraction or cesarean delivery during labor than among uncomplicated vaginal delivery or elective cesarean delivery, suggesting that abnormal labor rather than the mode of delivery constitutes the major risk factor for neonatal intracranial hemorrhage.14 Another large retrospective study found, however, a higher incidence of subarachnoidal hemorrhages after vacuum extractions (0.06%) than after forceps application (0.01%) or after spontaneous vaginal deliveries (0.01%).15
Other complications, such as cephalhematoma, scalp edema, and nondepressed fracture are usually not considered of clinical significance because they resolve spontaneously without treatment.9 Rarely, cases of growing skull fractures have been reported as a complication of cranial fractures in the young infant.3,25
In the present series of patients, we found an incidence of cephalhematoma (10.84%) similar to those generally reported (4–26%),1,8,16–19 but a lower incidence of scalp edema (18.73% compared with 28%),26 and no cases of subgaleal hemorrhage compared with what is reported (0–21%).8,13,17,18,20,21 Nevertheless, we observed more intracranial hemorrhages (0.87% compared with 0.11–0.34%),1,8,14,15,22 and more skull fracture (5.04% compared with 0–0.5%) than generally estimated.1,6,26 It is not possible to assess whether this higher incidences of intracranial hemorrhage and skull fractures are due to increased trauma or to systematic screening using transfontanellar ultrasonography and skull X-ray. Because seven of the eight intracranial hemorrhages were asymptomatic, subependymal, and plexus hemorrhages, we may assume that without ultrasonographic screening, only one case of symptomatic subarachnoidal and subdural hemorrhage would have been diagnosed, which coincides with an incidence of 0.11%, comparable then to what is found by others who did not systematically use ultrasonography.14 Similarly, the surprisingly high frequency of cranial bone fractures that we observed is probably related to the systematic radiologic screening during the postpartum period. Alternatively, we cannot rule out that some of these fractures could be the consequence of more aggressive management. All the fractures, however, were linear, and the newborns were asymptomatic. None of them required therapy, suggesting that they are not the consequences of aggressive extraction. A further argument is also the total absence of subgaleal hemorrhages in our series of patients. On the other hand, some mild cases of scalp edema may have gone undetected, because it typically resolves itself in 48–72 hours and the skull X-ray did not always occur within the first 2 days after birth. This study may therefore have underestimated the incidence of this complication.
The long-term clinical significance of complications (cephalhematomas, skull fractures, and scalp edema) could unfortunately not be evaluated, because no systematized data about neurodevelopmental evolution were included in our databank. We identified a number of risk factors associated with cephalhematomas, skull fractures, scalp edema, and intracranial hemorrhage, but no combination of risk factors could accurately predict either event nor any combination of these events. Application of the cup at mid or low station and its dislodgement are risk factors for cephalhematoma. Other studies have shown that cephalhematomas are more common in male infants and in nulliparous mothers, and also more frequent after prolonged application of the cup or of its paramedian placement.16,27
In our study, the only risk factor which seemed predictive for intracranial hemorrhage was asynclitism, with an RR of 10. But we should consider the fact that asynclitism may also be present and underreported in uncomplicated expulsions. Although no other predictive factors for intracranial hemorrhage were found, we assume that the case of intracranial hemorrhage which occurred in the caesarian group could be related to the several episodes of cup dislodgement. Therefore, difficult vacuum extractions and sudden cup detachment should be avoided to prevent intracranial hemorrhage.10
We found no correlation between fetal characteristics, such as birth weight and the neonatal complications, but this may be due to a selection bias, because women with an expected macrosomic fetus and especially when gestational diabetes was diagnosed, or when dyscinesia occurred underwent a cesarean delivery more often.
In our series, nulliparity, elderly multiparity, dislodgement of the cup and cephalhematoma were associated with cranial fracture. The high incidence of cranial fractures reported in the caesarean group (22.6%) may be due to frequent dislodgments linked to failed vacuum extraction. Cranial fractures (21.4%) and cephalhematomas (21.4%) frequently occurred even after easy extraction in a premature delivery, suggesting that these complications could be related to the prematurity itself.
In this series, systematic skull X-ray resulted in the diagnosis of complications that are not clinically significant, such as nondepressed fracture, cephalhematoma, and scalp edema. Because therapeutic intervention is usually not necessary to treat these conditions, we conclude that systematic skull X-ray is not useful after vacuum delivery. Nevertheless, in cases of suspected depressed skull fracture or neurologic symptoms, investigations such as skull X-ray and cranial CT are indicated.7
This study has limitations inherent to a retrospective analysis. Some data were missing. Indeed, some patients left the hospital earlier and did not have the chance of having a skull X-ray and ultrasonography performed. These were mostly patients without suspicion of complications. We may therefore have slightly overestimated the rate of complications. Furthermore, X-ray was not always performed during the first 2 days of life, and we may have underestimated the frequency of mild scalp edema. In summary, in this large series of successful vacuum extractions, performed on mature infants, severe neonatal complications associated with the technique were relatively rare events. We do, however, suggest that all infants delivered by vacuum extraction should be carefully and frequently examined. Systematic X-ray and ultrasonographic examination led to discovery of mainly asymptomatic complications. Because the clinical significance of these complications is unknown, we do not recommend the latter investigation methods as routine screening tools.
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© 2007 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.