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Comparison between metal cup and silicone rubber cup vacuum extractor
European Journal of Obstetrics & Gynecology and Reproductive Biology, 45 (1992) 173-176 0 1992 Elsevier Science Publishers B.V. All rights reserved 00262243/92/$05.00
173
EUROBS 1380
Comparison between metal cup and silicone rubber cup vacuum extractor C. Loghis, E. Pyrgiotis,
N. Panayotopoulos,
L. Batalias,
E. Salamalekis
and P.A. Zourlas
2nd Department of Obstetrics and Gynecology, University of Athens, Areteion Hospital, Athens, Greece
Accepted for publication 1 April 1992
Summary A total of 400 primiparous patients who were delivered by vacuum extractor were studied. The patients were divided in two groups: Group A included 200 patients who were delivered by metal cup vacuum extractor and Group B consisted of 200 patients who were delivered by rubber cup vacuum extractor. There were no statistically significant differences in the mean maternal age, mean gestational age, mean neonatal birth weight, indications for operative delivery, occipital positions and head stations between the two groups. No differences were found in the rates of birth canal trauma (11% vs. 12.5%), major neonatal scalp trauma (6.5% vs. 5.5%), neonatal jaundice (15.5% vs. 13.5%) and Apgar score. From this study we can conclude that both metal and silicone cups are equally satisfactory for vacuum extraction. Metal cup; Silicone rubber vacuum extractor
Introduction Vacuum extractor has gained popularity over forceps in assisted vaginal delivery in Continental Europe but has remained unpopular in the UK and North America, although some recent studies have encouraged its use [1,2]. It has been reported that the vacuum extractor may cause scalp trauma and cranial injuries, but, if it is applied carefully and when indicated, results are satisfactory. On the other hand, forceps delivery has more severe hazards and complications and requires a highly trained and much more experi-
enced person to avoid severe traumas, both to the mother and fetus. This is why the metal cup, first used by Malstrom, is nowadays widely accepted. Recently, a new vacuum extractor consisting of silicone rubber has been introduced by Kobayashi 131. In Greece, the metal vacuum extractor has always been popular, since it was introduced. At the moment both metal and rubber cup extractors are equally popular. In our study we present our experience and comparison between the metal and silicone rubber cup. Patients and Methods
Correspondence
Gynecology, Greece.
to: E. Salamalekis, Ass. Prof. Obstetrics and 30 Roumelis st., 15233 Chalandri, Athens,
Since the rubber cup was introduced in our clinic, a total of 400 primiparous patients requir-
174
ing assisted delivery were randomly selected (every second patient) to be delivered by metal or rubber cup vacuum extractor. The patients of our study were divided in two groups: group A included 200 patients delivered by metal cup extractor and group B consisted of 200 patients delivered by rubber cup extractor. All patients had singleton pregnancies, cephalic presentation and a gestational age of at least 37 weeks. The characteristics of the patients, such as maternal age, spontaneous or induced onset of labor, cardiotocographic monitoring and indications for operative delivery, were recorded. As soon as the decision to use assisted vaginal delivery was made, the position of the head and station were also recorded. All patients had full dilatation at delivery. Three sizes of metal cups were used, 40, 50 and 60 mm in diameter. The rubber cups (Silk cup by Menox, Sweden) were 50 and 60 mm in diameter. Vacuum was produced by a portable electric pump which provided progressive negative pressure gradients, with an upper limit of 600 mmHg. The neonate was examined immediately after birth by a paediatrician. Apgar score, neonatal birthweight and scalp traumas were recorded. Scalp markings were divided into: ‘minor’ (small bruising or abrasion) or ‘major’ (big bruising or cephalhaematoma). Neonatal jaundice was also assessed by serum bilirubin levels at 48 h after delivery. Levels of > 12 mg per dl were defined as jaundice, since all neonates were over 2500 g in weight. A detailed description of maternal trauma was recorded by the doctor immediately after delivery. Statistical analysis was performed by using the X2-test for frequency variables and the Student’s f-test for continuous variables. Results The characteristics of the patient groups are presented in Table I. Mean maternal age and mean neonatal birthweight were similar in the two groups. The rates of spontaneous onset of labor were 73% in group A vs. 78% in group B
TABLE I Characteristics of patients in two study groups Descriptive variables
Group A (metal cup)
Group B (silicone cup)
Number of deliveries Maternal age (years, mean) Birthweight (kg, mean) Onset of labour Spontaneous Induced Indication for operative delivery Delayed second stage Fetal distress Contraindication for expulsive efforts Occipital position Anterior Posterior Transverse Head station Mid-cavity Outlet
200 24.48 3.33
200 24.40 3.30
146 (73%) 54 (27%)
156 (78%) 44 (22%)
131 (65.5%) 62 (31%)
114 (57%) 70 (35%)
7 (3.5%)
16 (8%)
97 (48.5%) 87 143.5%) 16 (8%) 19 (9.5%) 181(90.5%)
95 (47.5%) 93 (46.5%) 12 (6%) 12 (6%) 188 (94%)
(NS). Indications for assisted delivery were: delayed second stage in 65.5% of cases in group A vs. 57% in group B (NS), fetal distress in 31% and 35%, respectively (NS), and contraindications for expulsive effort in 3.5% and 8%, respectively (NS). The rates of occipital position were: anterior 48.5% in group A and 47.5% in group B, posterior in 43.5% and 46.5% respectively and transverse in 8% and 6%. No statistical difference was found between the two groups. Head station at delivery was in the mid-cavity in 9.5% of the cases in group A and 6% in group B and at the outlet in 90.5% of cases in group A and 94% in group B (NS). Deliveries were effected without cup detachments in 182 cases (91%) using a rubber cup, and in 184 cases (92%) using a metal cup. The complications of deliveries with regard to mothers and neonates are shown in Table II. Episiotomy was performed in all cases during the end of the second stage, when the perineum was distended by the fetal head. The rates of first degree tear, trauma extension to anal sphincter and extension to vaginal vaults were found to be
175 TABLE
II
Complications
of assisted
deliveries
Complications
Group
A
Group
B
First degree tear Extension to anal sphincter Extension to vaginal vaults Neonatal scalp trauma Minor Major Jaundice Apgar score < 7 at 1 min
11 (5.5%) 6 (3.0%) 5 (2.5%)
13 (6.5%) 7 (3.5%) 5 (2.5%)
62 (31%) 13 (6.5%) 31 115.5%) IO (5.0%)
73 11 27 12
(36.5%) (5.5%) (13.5%) (6.0%)
similar in the two groups. No differences were found in the rates of neonatal scalp trauma, either minor or major, in the two groups. The rates of neonatal jaundice and Apgar score < 7 were similar in the two groups. Discussion
During the last 40 years Malstrom cup has increasingly gained popularity, especially in continental Europe 141.There is a considerable overlap of the indications for vacuum extraction and forceps delivery, and in many cases the choice of instrument is a matter of preference [5]. There is consensus that maternal trauma resulting from vacuum extraction is less than that from forceps delivery [6]. The rubber cup, being a new evolutionary step in vacuum extraction, is less liable to cause vaginal or scalp trauma [7]. The aim of this study was to compare the silicone rubber cup with the more commonly used in Greece metal cup’vacuum extractor in clinical practice. No failures were noted with either instrument, because we have been very strict with the indications and conditions under which we performed vacuum extraction. In all cases the fetal‘ ‘head should have been at least in the mid pelvis and the cervix fully dilated. Traction was applied only during uterine contractions. In the case of cup detachment, the procedure was completed by a qualified obstetrician, thus minimizing the factor of ‘teaching hospital complications’. Using the metal cup we had no detachments in 92.2% of our cases, compared with 91% in the cases with rubber cup. Our rate using the metal cup is
similar to other authors’ [1,4]. Cohn et al. [l] in a multicentre randomized trial report a lower rate (80%) with no detachment, using the rubber cup, probably because the cup was applied in several cases without complete cervical dilatation. In the assessment of birth canal trauma, no difference was found between the two groups. The rates of perineal and vaginal trauma were similar in the two groups. Certain authors believe that the soft edge of the rubber cup causes fewer lacerations though they noted no statistical difference in their cases [l]. The condition of the neonates immediately after birth was similar in the two groups. The rates of major scalp trauma, assessed 48 hours later, were low in both groups, while jaundice was equally frequent in both groups. Minor neonatal scalp trauma seems to be nearly unavoidable but the formation of this “shignon” is unavoidable in order to obtain traction through vacuum application. As ‘major scalp trauma’ we describe the formation of cephalhaematoma, which is sharply delineated by the scalp raphae and was noted in only 6.5O/c in metal cup and 5.5% in rubber cup extractions. Most authors report a similar rate of about 6% in cephalhaematoma formation [1,8,9]. In the case of detachment, the separation of the rubber cup is much more gentle than the abrupt separation of the metal cup and this is a most favorable factor for the neonate. In condusion, we believe that both types of cups are equally effective in obstetrical practice, and that the rubber cup, which is an innovation, may have an important place in modern obstetrics. References Cohn M. Barclay C, Fraser R, Zaclama M, Johanson R, Anderson D, Walker C. A multicentre randomized trial comparing delivery with a silicone rubber cup and rigid metal vacuum extractor cups. Br J Obstet Gynaecol 1989;96:545-551. Fall 0, Ryder G, Finnstrom K, Finnstrom 0, Leigon I. Forceps or vacuum extraction? A comparison of effects on the newborn infant. Acta Obstet Gynecol Stand 1986;65:75-80. Hammarstrom M, Csemiczky G, Belfrage P. Comparison between the conventional Malmstrom extractor and a new extractor with silastic cup. Acta Obstet Gynecol Stand 1986;65:791-792.
176 4 Vacca A, Grant A, Wyatt G, Chalmers I. Portsmouth operative delivery trial: a comparison of vacuum extraction and forceps delivery. Br J Obstet Gynaecol 1983;90:11071112. 5 Hofmeyr GJ, Gobetz L, Sonnendecker EW, Turner M. New design rigid and soft vacuum extractor cups: a preliminary comparison of traction forces. Br J Obstet Gynaecol 1990;97:681-685. 6 Ryden G. Vacuum extractor or forceps? Br Med J 1986;292:75-77.
7 Dell DL, Sightle SE, Plauche WC. Soft cup vacuum extraction; a comparison of outlet delivery. Obstet Gynecol 1985;66:624-628. 8 Johanson R, Pusey J, Livera N, Jones P. North Staffordshire/Wigan assisted delivery trial. Br J Obstet Gynaecol 1989;96:537-544. 9 Plauche WC. Fetal cranial injuries related to delivery with the Malmstrom vacuum extractor. Obstet Gynecol 1979,53:750-757.
173
EUROBS 1380
Comparison between metal cup and silicone rubber cup vacuum extractor C. Loghis, E. Pyrgiotis,
N. Panayotopoulos,
L. Batalias,
E. Salamalekis
and P.A. Zourlas
2nd Department of Obstetrics and Gynecology, University of Athens, Areteion Hospital, Athens, Greece
Accepted for publication 1 April 1992
Summary A total of 400 primiparous patients who were delivered by vacuum extractor were studied. The patients were divided in two groups: Group A included 200 patients who were delivered by metal cup vacuum extractor and Group B consisted of 200 patients who were delivered by rubber cup vacuum extractor. There were no statistically significant differences in the mean maternal age, mean gestational age, mean neonatal birth weight, indications for operative delivery, occipital positions and head stations between the two groups. No differences were found in the rates of birth canal trauma (11% vs. 12.5%), major neonatal scalp trauma (6.5% vs. 5.5%), neonatal jaundice (15.5% vs. 13.5%) and Apgar score. From this study we can conclude that both metal and silicone cups are equally satisfactory for vacuum extraction. Metal cup; Silicone rubber vacuum extractor
Introduction Vacuum extractor has gained popularity over forceps in assisted vaginal delivery in Continental Europe but has remained unpopular in the UK and North America, although some recent studies have encouraged its use [1,2]. It has been reported that the vacuum extractor may cause scalp trauma and cranial injuries, but, if it is applied carefully and when indicated, results are satisfactory. On the other hand, forceps delivery has more severe hazards and complications and requires a highly trained and much more experi-
enced person to avoid severe traumas, both to the mother and fetus. This is why the metal cup, first used by Malstrom, is nowadays widely accepted. Recently, a new vacuum extractor consisting of silicone rubber has been introduced by Kobayashi 131. In Greece, the metal vacuum extractor has always been popular, since it was introduced. At the moment both metal and rubber cup extractors are equally popular. In our study we present our experience and comparison between the metal and silicone rubber cup. Patients and Methods
Correspondence
Gynecology, Greece.
to: E. Salamalekis, Ass. Prof. Obstetrics and 30 Roumelis st., 15233 Chalandri, Athens,
Since the rubber cup was introduced in our clinic, a total of 400 primiparous patients requir-
174
ing assisted delivery were randomly selected (every second patient) to be delivered by metal or rubber cup vacuum extractor. The patients of our study were divided in two groups: group A included 200 patients delivered by metal cup extractor and group B consisted of 200 patients delivered by rubber cup extractor. All patients had singleton pregnancies, cephalic presentation and a gestational age of at least 37 weeks. The characteristics of the patients, such as maternal age, spontaneous or induced onset of labor, cardiotocographic monitoring and indications for operative delivery, were recorded. As soon as the decision to use assisted vaginal delivery was made, the position of the head and station were also recorded. All patients had full dilatation at delivery. Three sizes of metal cups were used, 40, 50 and 60 mm in diameter. The rubber cups (Silk cup by Menox, Sweden) were 50 and 60 mm in diameter. Vacuum was produced by a portable electric pump which provided progressive negative pressure gradients, with an upper limit of 600 mmHg. The neonate was examined immediately after birth by a paediatrician. Apgar score, neonatal birthweight and scalp traumas were recorded. Scalp markings were divided into: ‘minor’ (small bruising or abrasion) or ‘major’ (big bruising or cephalhaematoma). Neonatal jaundice was also assessed by serum bilirubin levels at 48 h after delivery. Levels of > 12 mg per dl were defined as jaundice, since all neonates were over 2500 g in weight. A detailed description of maternal trauma was recorded by the doctor immediately after delivery. Statistical analysis was performed by using the X2-test for frequency variables and the Student’s f-test for continuous variables. Results The characteristics of the patient groups are presented in Table I. Mean maternal age and mean neonatal birthweight were similar in the two groups. The rates of spontaneous onset of labor were 73% in group A vs. 78% in group B
TABLE I Characteristics of patients in two study groups Descriptive variables
Group A (metal cup)
Group B (silicone cup)
Number of deliveries Maternal age (years, mean) Birthweight (kg, mean) Onset of labour Spontaneous Induced Indication for operative delivery Delayed second stage Fetal distress Contraindication for expulsive efforts Occipital position Anterior Posterior Transverse Head station Mid-cavity Outlet
200 24.48 3.33
200 24.40 3.30
146 (73%) 54 (27%)
156 (78%) 44 (22%)
131 (65.5%) 62 (31%)
114 (57%) 70 (35%)
7 (3.5%)
16 (8%)
97 (48.5%) 87 143.5%) 16 (8%) 19 (9.5%) 181(90.5%)
95 (47.5%) 93 (46.5%) 12 (6%) 12 (6%) 188 (94%)
(NS). Indications for assisted delivery were: delayed second stage in 65.5% of cases in group A vs. 57% in group B (NS), fetal distress in 31% and 35%, respectively (NS), and contraindications for expulsive effort in 3.5% and 8%, respectively (NS). The rates of occipital position were: anterior 48.5% in group A and 47.5% in group B, posterior in 43.5% and 46.5% respectively and transverse in 8% and 6%. No statistical difference was found between the two groups. Head station at delivery was in the mid-cavity in 9.5% of the cases in group A and 6% in group B and at the outlet in 90.5% of cases in group A and 94% in group B (NS). Deliveries were effected without cup detachments in 182 cases (91%) using a rubber cup, and in 184 cases (92%) using a metal cup. The complications of deliveries with regard to mothers and neonates are shown in Table II. Episiotomy was performed in all cases during the end of the second stage, when the perineum was distended by the fetal head. The rates of first degree tear, trauma extension to anal sphincter and extension to vaginal vaults were found to be
175 TABLE
II
Complications
of assisted
deliveries
Complications
Group
A
Group
B
First degree tear Extension to anal sphincter Extension to vaginal vaults Neonatal scalp trauma Minor Major Jaundice Apgar score < 7 at 1 min
11 (5.5%) 6 (3.0%) 5 (2.5%)
13 (6.5%) 7 (3.5%) 5 (2.5%)
62 (31%) 13 (6.5%) 31 115.5%) IO (5.0%)
73 11 27 12
(36.5%) (5.5%) (13.5%) (6.0%)
similar in the two groups. No differences were found in the rates of neonatal scalp trauma, either minor or major, in the two groups. The rates of neonatal jaundice and Apgar score < 7 were similar in the two groups. Discussion
During the last 40 years Malstrom cup has increasingly gained popularity, especially in continental Europe 141.There is a considerable overlap of the indications for vacuum extraction and forceps delivery, and in many cases the choice of instrument is a matter of preference [5]. There is consensus that maternal trauma resulting from vacuum extraction is less than that from forceps delivery [6]. The rubber cup, being a new evolutionary step in vacuum extraction, is less liable to cause vaginal or scalp trauma [7]. The aim of this study was to compare the silicone rubber cup with the more commonly used in Greece metal cup’vacuum extractor in clinical practice. No failures were noted with either instrument, because we have been very strict with the indications and conditions under which we performed vacuum extraction. In all cases the fetal‘ ‘head should have been at least in the mid pelvis and the cervix fully dilated. Traction was applied only during uterine contractions. In the case of cup detachment, the procedure was completed by a qualified obstetrician, thus minimizing the factor of ‘teaching hospital complications’. Using the metal cup we had no detachments in 92.2% of our cases, compared with 91% in the cases with rubber cup. Our rate using the metal cup is
similar to other authors’ [1,4]. Cohn et al. [l] in a multicentre randomized trial report a lower rate (80%) with no detachment, using the rubber cup, probably because the cup was applied in several cases without complete cervical dilatation. In the assessment of birth canal trauma, no difference was found between the two groups. The rates of perineal and vaginal trauma were similar in the two groups. Certain authors believe that the soft edge of the rubber cup causes fewer lacerations though they noted no statistical difference in their cases [l]. The condition of the neonates immediately after birth was similar in the two groups. The rates of major scalp trauma, assessed 48 hours later, were low in both groups, while jaundice was equally frequent in both groups. Minor neonatal scalp trauma seems to be nearly unavoidable but the formation of this “shignon” is unavoidable in order to obtain traction through vacuum application. As ‘major scalp trauma’ we describe the formation of cephalhaematoma, which is sharply delineated by the scalp raphae and was noted in only 6.5O/c in metal cup and 5.5% in rubber cup extractions. Most authors report a similar rate of about 6% in cephalhaematoma formation [1,8,9]. In the case of detachment, the separation of the rubber cup is much more gentle than the abrupt separation of the metal cup and this is a most favorable factor for the neonate. In condusion, we believe that both types of cups are equally effective in obstetrical practice, and that the rubber cup, which is an innovation, may have an important place in modern obstetrics. References Cohn M. Barclay C, Fraser R, Zaclama M, Johanson R, Anderson D, Walker C. A multicentre randomized trial comparing delivery with a silicone rubber cup and rigid metal vacuum extractor cups. Br J Obstet Gynaecol 1989;96:545-551. Fall 0, Ryder G, Finnstrom K, Finnstrom 0, Leigon I. Forceps or vacuum extraction? A comparison of effects on the newborn infant. Acta Obstet Gynecol Stand 1986;65:75-80. Hammarstrom M, Csemiczky G, Belfrage P. Comparison between the conventional Malmstrom extractor and a new extractor with silastic cup. Acta Obstet Gynecol Stand 1986;65:791-792.
176 4 Vacca A, Grant A, Wyatt G, Chalmers I. Portsmouth operative delivery trial: a comparison of vacuum extraction and forceps delivery. Br J Obstet Gynaecol 1983;90:11071112. 5 Hofmeyr GJ, Gobetz L, Sonnendecker EW, Turner M. New design rigid and soft vacuum extractor cups: a preliminary comparison of traction forces. Br J Obstet Gynaecol 1990;97:681-685. 6 Ryden G. Vacuum extractor or forceps? Br Med J 1986;292:75-77.
7 Dell DL, Sightle SE, Plauche WC. Soft cup vacuum extraction; a comparison of outlet delivery. Obstet Gynecol 1985;66:624-628. 8 Johanson R, Pusey J, Livera N, Jones P. North Staffordshire/Wigan assisted delivery trial. Br J Obstet Gynaecol 1989;96:537-544. 9 Plauche WC. Fetal cranial injuries related to delivery with the Malmstrom vacuum extractor. Obstet Gynecol 1979,53:750-757.