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Combined simple and complex cord knots
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European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
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Case report
Combined simple and complex cord knots Ralph N. Roberts Glasgow Royal Maternity Hospital, Rottenrow, GlasgowG40NA, Scotland Accepted 31 March 1994
Abstract Both double true knots and complex knots of the umbilical cord are rare events. This report presents a case in which the two occurrences were combined. Apart from some early decelerations in the first stage of labour, there was no evidence of fetal compromise. A mid-cavity forceps delivery performed for poor maternal effort resulted in the birth of a healthy female infant. The mechanism and consequences of umbilical cord knotting are reviewed.
Keywords: Umbilical cord; True knot
1. Introduction The incidence of true knots of the umbilical cord has been reported as between 0.3 and 2.1% [1,2]. Predisposing factors are a long umbilical cord, polyhydramnios, multiparity, a small fetus and monoamniotic twins. It has also been reported to be more common with male fetuses [3]. This is presumably because, on average, the umbilical cords of male fetuses are longer than those of females [4]. A double true knot of the cord is a much rarer event than a single knot, the reported incidence being 0.1% [5l. Complex knots, which are usually in the form of a figure of eight, are also rare, but their incidence has not been defined. The combination of a simple and a complex true knot, as described in this paper, is a highly unusual phenomenon with only one previous report in the world literature [6].
2. Case report A 25 year old para 2 + 1 was admitted for induction of labour at 38 +I weeks' gestation. Her two previous babies had been delivered by Kielland's forceps, and the second had both a true cord knot and a loop of cord
around the neck. This pregnancy had been uneventful and a normal liquor volume had been reported on ultrasound scan 2 weeks previously. A 3 mg PGE2 pessary was administered at 10 pm on the night of admission and at 6 am the following morning. Initially the fetal head was not well applied to the cervix so a syntocinon infusion was commenced prior to artificial rupture of the membranes. Labour was monitored by continuous cardiotocography using a fetal scalp electrode. The first stage of labour lasted 2 h, during which there were episodes of recurrent early decelerations, but the troughs were never lower than 90 beats per minute and recovery was always rapid. These decelerations settled during the second stage, but delivery was expedited by Neville Barnes forceps because of poor maternal effort. A female infant weighing 3395 g was delivered. Apgar scores were 7 at I rain and 9 at 5 min. The umbilical cord was found to have two true knots, one of which was complex in nature. The cord was 84 cm in length with the knots in situ, and 93 cm with the knots unravelled. The knots were situated 31 cm and 46 cm from the placental insertion. Fig. 1 shows a photograph of the two knots with a diagramatic representation of their positions and configurations. The puerperium was uneventful and no neonatal problems were encountered.
0301-2115/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0301-2115(95)02131-B
R.N. RobertsI European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
132
mm~O
20
30
40
50
60
70
80
~(
38 cm
31 cm
Fig. I. The two cord knots with a diagramatic representation of their location and configuration.
3. Discussion
It is presumed that the mechanism by which a true knot of the umbilical cord occurs involves the formation of a loop of cord of sufficient length that the fetus can move through it. The absolute prerequsite is, therefore, a cord which is long enough for this to happen; the chance of it then occurring is related to factors allowing more room for fetal movement, such as multiparity, polyhydramnios or a small fetus. McClennan et al. [7] in a study of I l l 5 umbilical cords reported the 10th,
50th and 90th percentile lengths as 44 cm, 52 cm and 69 cm. The cord length in the case I have described was thus > 90th centile and the risk of knotting was increased by the mother's multiparity and perhaps the previous history of cord knot which indicated a susceptibility to predisposing conditions. There has been debate as to the gestation period at which knotting of the cord can occur, and when it is most likely. It may happen during parturition as described by Atwood [8], but it seems unlikely that this is the most common time. In view of the facts that true knots may be found in the cords of aborted fetuses [9] and cord length does not increase significantly after 28 weeks' [4], it has been suggested by Blickstein et al. [3] that true knots are most likely to be formed after 9 weeks' and before 28 weeks' gestation. A newly formed knot can be distinguished from an old knot by the fact that there is no loss of Wharton's jelly and no marked groove at the site of the knot. True cord knots may be directly associated with intrauterine death [10]. McLennan et al., [7] drawing from perinatal mortality data in the state of Victoria, reported that 2% of babies with cord knots are stillborn, and that these births account for 5% of all stillbirths of infants weighing >2500 g. However, in the vast majority of cases they do not harm the fetus. In contrast, much higher rates of perinatal mortality (25%) and morbidity (25%) have been reported in association with double true knots [1 l]. Whether or not the fetus comes to harm is probably related to whether or not the venous perfusion pressure is raised. In-vitro studies by Browne [12] showed that the pressure required to perfuse the umbilical vein increased with increasing number of knots and the tightness of the knots. He demonstrated that that even a slack knot impairs perfusion in the umbilical vein. However, this was challenged by Chasnoff and Fletcher [13] who performed in-vitro studies with artificial knots formed in normal cords. They showed that a loose knot did not affect venous perfusion, but as the knot tightened the cord diameter reduced and the pressure required to perfuse beyond the knot increased. Unfortunately, examination of the knot after delivery of the fetus cannot indicate how tight it was in-utero because of the inevitable traction during parturition. Animal experiments in umbilical vein occlusion have shown that a decrease in umbilical blood flow would only jeopardise the fetus when a critical flow rate is reached, as oxygen consumption and oxygen saturation in the fetal circulation are relatively well maintained with a reduction in flow down to 50% of the normal value [14]. However, as the umbilical blood flow increases with advancing gestation, the obstructive effect of a cord knot will be more pronounced in the latter part of pregnancy, and with increasing gestation a critical point may be reached when the reduction in blood flow would produce hypoxaernia in the fetus.
R.N. Roberts/ European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
It is difficult to speculate whether the decelerations in fetal heart rate noted during the first stage of labour in the case described could be attributed to the presence of the two cord knots. There would appear to be more likelihood of external compression of the umbilical cord during uterine contractions in the presence of a true knot, due to the increased bulk of the cord at that point. The risk of compression would be doubled in the presence of two knots, and further increased with a complex knot because of its greater bulk. The likelihood of such compression is obviously increased following rupture of the membranes. In-utero detection of true knots of the umbilical cord has become easier with high resolution ultrasound and, in particular, doppler flow studies on the umbilical vessels. However, in view of the relatively low incidence of complications, it is unlikely that antenatal diagnosis would affect management unless associated with other adverse features.
Acknowledgements I would like to acknowledge Dr. J. N. H. Ferris, the consultant in charge at Ards Hospital, Northern Ireland, for his permission to report this case. I would also like to thank Mr. T. McFetters and Mr. E. Pinner for photographic and graphical assistance.
133
References [ll Lundgren AT, Boice WA. True knotting of the umbilical cord. Illinois Med J 1939; 76: 451-8. [2] Dippel AL. Maligned umbilical cord entanglements. Am J Obstet Gynecol 1964; 88: 1012-1019. [3] Blickstein I, Shoham-Schwartz Z, Lancet M. Predisposing factors in the formation of true knots of the umbilical cord - Analysis of morphometric and perinatal data. lnt J Gynaecoi Obstet 1987; 25: 395-398. [4] Walker CW, lye BG. The length of the human umbilical cord: a statistical report. Br Med J 1960; h 546-548. [5] Hartge R. Uber das vorkommen yon nabeischnurknoten: Geburtschilfe und Frauenheilkunde. 1979; 39: 976-980. [6] Fleming HG. An umbilical freak. Texas State J Med 1924; 19: 579. [7l McLennan H, Price E, Urbanska M, Craig N, Fraser M. Umbilical cord knots and encirclements. Aust NZ J Obstet Gynaecol 1988; 28: 116-119. [8] Atwood WG. Knotting of the umbilical cord. Surg Gynecol Obstet 1932; 55: 96-99. [9] Javert CT, Barton B. Congenital and acquired lesions of the umbilical cord and spontaneous abortion. Am J Obstet Gynecol 1952; 63: 1065-1077. [10] Hennessy JP. True knots of the umbilical cord. Am J Obstet Gynecol 1944; 48: 528-536. Ill] H~nigl W, Urdl W, Hoffman HMH, Mayer HO. Doppelter echter nabelschnurknoten und geburtsverlauf. Gyn~ik Rdsch 1988; 28 (suppl 2): 155-157. [12] Browne FJ. On the abnormalities of the umbilical cord which may cause antenatal death. J Obstet Gynaec Brit Emp 1944; 32: 17-48.
[13] Chasnoff 1J, Fletcher MA. True knot of the umbilical cord. Am J Obstet Gynecol 1977; 127: 425-427. [14] ltskovitz J, LaGamma EF, Rudolph AM. The effect of reducing umbilical blood flow on fetal oxygenation. Am J Obstet Gynecol 1983; 145: 813-818.
,
:("
,
'y"
,|
European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
. . . .
, o , . ° . °
. . . . . .
•
. . . .
Case report
Combined simple and complex cord knots Ralph N. Roberts Glasgow Royal Maternity Hospital, Rottenrow, GlasgowG40NA, Scotland Accepted 31 March 1994
Abstract Both double true knots and complex knots of the umbilical cord are rare events. This report presents a case in which the two occurrences were combined. Apart from some early decelerations in the first stage of labour, there was no evidence of fetal compromise. A mid-cavity forceps delivery performed for poor maternal effort resulted in the birth of a healthy female infant. The mechanism and consequences of umbilical cord knotting are reviewed.
Keywords: Umbilical cord; True knot
1. Introduction The incidence of true knots of the umbilical cord has been reported as between 0.3 and 2.1% [1,2]. Predisposing factors are a long umbilical cord, polyhydramnios, multiparity, a small fetus and monoamniotic twins. It has also been reported to be more common with male fetuses [3]. This is presumably because, on average, the umbilical cords of male fetuses are longer than those of females [4]. A double true knot of the cord is a much rarer event than a single knot, the reported incidence being 0.1% [5l. Complex knots, which are usually in the form of a figure of eight, are also rare, but their incidence has not been defined. The combination of a simple and a complex true knot, as described in this paper, is a highly unusual phenomenon with only one previous report in the world literature [6].
2. Case report A 25 year old para 2 + 1 was admitted for induction of labour at 38 +I weeks' gestation. Her two previous babies had been delivered by Kielland's forceps, and the second had both a true cord knot and a loop of cord
around the neck. This pregnancy had been uneventful and a normal liquor volume had been reported on ultrasound scan 2 weeks previously. A 3 mg PGE2 pessary was administered at 10 pm on the night of admission and at 6 am the following morning. Initially the fetal head was not well applied to the cervix so a syntocinon infusion was commenced prior to artificial rupture of the membranes. Labour was monitored by continuous cardiotocography using a fetal scalp electrode. The first stage of labour lasted 2 h, during which there were episodes of recurrent early decelerations, but the troughs were never lower than 90 beats per minute and recovery was always rapid. These decelerations settled during the second stage, but delivery was expedited by Neville Barnes forceps because of poor maternal effort. A female infant weighing 3395 g was delivered. Apgar scores were 7 at I rain and 9 at 5 min. The umbilical cord was found to have two true knots, one of which was complex in nature. The cord was 84 cm in length with the knots in situ, and 93 cm with the knots unravelled. The knots were situated 31 cm and 46 cm from the placental insertion. Fig. 1 shows a photograph of the two knots with a diagramatic representation of their positions and configurations. The puerperium was uneventful and no neonatal problems were encountered.
0301-2115/95/$09.50 © 1995 Elsevier Science Ireland Ltd. All rights reserved SSDI 0301-2115(95)02131-B
R.N. RobertsI European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
132
mm~O
20
30
40
50
60
70
80
~(
38 cm
31 cm
Fig. I. The two cord knots with a diagramatic representation of their location and configuration.
3. Discussion
It is presumed that the mechanism by which a true knot of the umbilical cord occurs involves the formation of a loop of cord of sufficient length that the fetus can move through it. The absolute prerequsite is, therefore, a cord which is long enough for this to happen; the chance of it then occurring is related to factors allowing more room for fetal movement, such as multiparity, polyhydramnios or a small fetus. McClennan et al. [7] in a study of I l l 5 umbilical cords reported the 10th,
50th and 90th percentile lengths as 44 cm, 52 cm and 69 cm. The cord length in the case I have described was thus > 90th centile and the risk of knotting was increased by the mother's multiparity and perhaps the previous history of cord knot which indicated a susceptibility to predisposing conditions. There has been debate as to the gestation period at which knotting of the cord can occur, and when it is most likely. It may happen during parturition as described by Atwood [8], but it seems unlikely that this is the most common time. In view of the facts that true knots may be found in the cords of aborted fetuses [9] and cord length does not increase significantly after 28 weeks' [4], it has been suggested by Blickstein et al. [3] that true knots are most likely to be formed after 9 weeks' and before 28 weeks' gestation. A newly formed knot can be distinguished from an old knot by the fact that there is no loss of Wharton's jelly and no marked groove at the site of the knot. True cord knots may be directly associated with intrauterine death [10]. McLennan et al., [7] drawing from perinatal mortality data in the state of Victoria, reported that 2% of babies with cord knots are stillborn, and that these births account for 5% of all stillbirths of infants weighing >2500 g. However, in the vast majority of cases they do not harm the fetus. In contrast, much higher rates of perinatal mortality (25%) and morbidity (25%) have been reported in association with double true knots [1 l]. Whether or not the fetus comes to harm is probably related to whether or not the venous perfusion pressure is raised. In-vitro studies by Browne [12] showed that the pressure required to perfuse the umbilical vein increased with increasing number of knots and the tightness of the knots. He demonstrated that that even a slack knot impairs perfusion in the umbilical vein. However, this was challenged by Chasnoff and Fletcher [13] who performed in-vitro studies with artificial knots formed in normal cords. They showed that a loose knot did not affect venous perfusion, but as the knot tightened the cord diameter reduced and the pressure required to perfuse beyond the knot increased. Unfortunately, examination of the knot after delivery of the fetus cannot indicate how tight it was in-utero because of the inevitable traction during parturition. Animal experiments in umbilical vein occlusion have shown that a decrease in umbilical blood flow would only jeopardise the fetus when a critical flow rate is reached, as oxygen consumption and oxygen saturation in the fetal circulation are relatively well maintained with a reduction in flow down to 50% of the normal value [14]. However, as the umbilical blood flow increases with advancing gestation, the obstructive effect of a cord knot will be more pronounced in the latter part of pregnancy, and with increasing gestation a critical point may be reached when the reduction in blood flow would produce hypoxaernia in the fetus.
R.N. Roberts/ European Journal of Obstetrics & Gynecology and Reproductive Biology 62 (1995) 131-133
It is difficult to speculate whether the decelerations in fetal heart rate noted during the first stage of labour in the case described could be attributed to the presence of the two cord knots. There would appear to be more likelihood of external compression of the umbilical cord during uterine contractions in the presence of a true knot, due to the increased bulk of the cord at that point. The risk of compression would be doubled in the presence of two knots, and further increased with a complex knot because of its greater bulk. The likelihood of such compression is obviously increased following rupture of the membranes. In-utero detection of true knots of the umbilical cord has become easier with high resolution ultrasound and, in particular, doppler flow studies on the umbilical vessels. However, in view of the relatively low incidence of complications, it is unlikely that antenatal diagnosis would affect management unless associated with other adverse features.
Acknowledgements I would like to acknowledge Dr. J. N. H. Ferris, the consultant in charge at Ards Hospital, Northern Ireland, for his permission to report this case. I would also like to thank Mr. T. McFetters and Mr. E. Pinner for photographic and graphical assistance.
133
References [ll Lundgren AT, Boice WA. True knotting of the umbilical cord. Illinois Med J 1939; 76: 451-8. [2] Dippel AL. Maligned umbilical cord entanglements. Am J Obstet Gynecol 1964; 88: 1012-1019. [3] Blickstein I, Shoham-Schwartz Z, Lancet M. Predisposing factors in the formation of true knots of the umbilical cord - Analysis of morphometric and perinatal data. lnt J Gynaecoi Obstet 1987; 25: 395-398. [4] Walker CW, lye BG. The length of the human umbilical cord: a statistical report. Br Med J 1960; h 546-548. [5] Hartge R. Uber das vorkommen yon nabeischnurknoten: Geburtschilfe und Frauenheilkunde. 1979; 39: 976-980. [6] Fleming HG. An umbilical freak. Texas State J Med 1924; 19: 579. [7l McLennan H, Price E, Urbanska M, Craig N, Fraser M. Umbilical cord knots and encirclements. Aust NZ J Obstet Gynaecol 1988; 28: 116-119. [8] Atwood WG. Knotting of the umbilical cord. Surg Gynecol Obstet 1932; 55: 96-99. [9] Javert CT, Barton B. Congenital and acquired lesions of the umbilical cord and spontaneous abortion. Am J Obstet Gynecol 1952; 63: 1065-1077. [10] Hennessy JP. True knots of the umbilical cord. Am J Obstet Gynecol 1944; 48: 528-536. Ill] H~nigl W, Urdl W, Hoffman HMH, Mayer HO. Doppelter echter nabelschnurknoten und geburtsverlauf. Gyn~ik Rdsch 1988; 28 (suppl 2): 155-157. [12] Browne FJ. On the abnormalities of the umbilical cord which may cause antenatal death. J Obstet Gynaec Brit Emp 1944; 32: 17-48.
[13] Chasnoff 1J, Fletcher MA. True knot of the umbilical cord. Am J Obstet Gynecol 1977; 127: 425-427. [14] ltskovitz J, LaGamma EF, Rudolph AM. The effect of reducing umbilical blood flow on fetal oxygenation. Am J Obstet Gynecol 1983; 145: 813-818.