- Email: [email protected]
Umbilical cord blood collection before placental delivery during cesarean delivery increases cord blood volume and nucleated cell number available for transplantation
Umbilical cord blood collection before placental delivery during cesarean delivery increases cord blood volume and nucleated cell number available for transplantation Daniel V. Surbek, MD,a Eva Visca, MD,a Christian Steinmann, MD,a André Tichelli, MD,b Stefan Schatt,a Sinuhe Hahn, PhD,a Alois Gratwohl, MD,c and Wolfgang Holzgreve, MD, MSa Basel, Switzerland OBJECTIVE: We sought to determine whether umbilical cord blood collection during cesarean delivery can be improved by collecting cord blood before delivery of the placenta. STUDY DESIGN: Patients undergoing cesarean delivery were randomly assigned to cord blood collection before or after placental delivery. Closed sterile collection systems were used for blood sampling. Cord blood characteristics and maternal outcome parameters were compared between the 2 groups. RESULTS: A total number of 40 patients were available for analysis. No differences in maternal and neonatal characteristics were found. A larger amount of cord blood volume (mean ± SEM, 93 ± 7.5 vs 66 ± 6.6 mL; P = .013) and total nucleated cell number (11.1 ± 1.2 vs 7.4 ± 0.8 × 108 cells; P = .026) was obtained in the samples collected before compared with those collected after placental delivery. Similarly, there was a trend toward higher total CD34+ cell number in samples collected in situ (30.0 ± 6.0 vs 17.4 ± 2.4 × 105 cells; P = .076). Estimated intraoperative blood loss, difference between prepartum and postpartum hemoglobin values, operating time, and puerperal infection rates were similar in both groups. CONCLUSION: If a cesarean delivery is performed, cord blood sampling is more efficacious if performed before delivery of the placenta. This collection method seems beneficial and safe and might therefore be preferably used for related, as well as unrelated, cord blood stem cell banking and transplantation. (Am J Obstet Gynecol 2000;183:218-21.)
Key words: Umbilical cord blood, hematopoietic stem cells, cesarean delivery, cord blood collection
Umbilical cord blood is increasingly used as an alternative source of hematopoietic stem cells for related1 and unrelated2 allogeneic transplantation in children and adolescents. Recent data show that clinical outcome of cord blood transplantation is influenced by the number of nucleated cells transplanted.3, 4 Therefore the yield of stem cells remains an important aim of cord blood collection in addition to donor (ie, maternal and neonatal) safety. The strategy of cord blood collection varies between different cord blood banks.5 Open systems, which were initially used for cord blood retrieval,6 have been replaced by closed systems with blood-collection bags to minimize the risk of contamination with bacteria or maternal cells.7 Some authors described cord blood collecFrom the Department of Obstetrics and Gynecology,a the Laboratory of Hematology, Department of Central Laboratories,b and the Division of Hematology, Department of Internal Medicine,c University of Basel. Received for publication July 29, 1999; revised December 2, 1999; accepted January 12, 2000. Reprint requests: Daniel V. Surbek, MD, Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital, Denmark Hill, London, United Kingdom SE5 9RS. Copyright © 2000 by Mosby, Inc. 0002-9378/2000 $12.00 + 0 6/1/105744 doi:10.1067/mob.2000.105744
218
tion at vaginal delivery after expulsion of the placenta,8 whereas others perform the collection while the placenta is still in utero9 or use a combination of the two.6 In a randomized trial we previously showed that cord blood collection during vaginal delivery is improved if performed before placental expulsion.10 If a cesarean delivery is performed for obstetric reasons, an optimal collection technique is also essential, especially if cord blood transplantation in a sibling is planned. There are, however, no prospective data about different cord blood-collection methods during cesarean delivery available to date. The aim of our study was to assess, in a randomized trial, whether cord blood collection before delivery of the placenta during cesarean delivery is superior to sampling from the delivered placenta by using a single umbilical vein puncture and a closed blood-collection system. Methods Study design. Pregnant women undergoing cesarean delivery at the Department of Obstetrics and Gynecology of the University Hospital of Basel were considered for inclusion into the study. Criteria for inclusion were singleton pregnancy, elective or secondary cesarean delivery, and willingness to participate in the study. Exclusion cri-
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teria were nonreassuring fetal heart rate, placenta previa, preterm birth, fetal growth restriction, maternal anemia with a hemoglobin level of <10 g/dL, and clinical chorioamnionitis. Informed consent was obtained from every subject before inclusion in the study. The study was approved by the institutional review board of the University Hospital. After inclusion and before cesarean delivery, women were randomized to group A (cord blood collection before placental delivery) or group B (cord blood collection after placental delivery) by means of random allocation of sealed opaque envelopes. Cord blood collection. Preoperative and postoperative management was according to standard protocol. Cesarean delivery was performed routinely by means of a low transverse uterine incision. After delivery of the newborn, the umbilical cord was double clamped and transected within 10 seconds, which is the standard procedure in our department. As soon as the newborn was removed from the operative field, 10 units of oxytocin was given intravenously. An umbilical cord fragment of 3 to 5 cm in length was obtained to assess arterial and venous cord blood acid-base status. Then in group A cord blood was collected as follows. The placenta-side part of the umbilical cord was held straight at a slight angle downward. After identification of a suitable puncture site, the umbilical cord was cleaned and disinfected with alcoholic polyvinylpyrrolidone-iodine solution. The umbilical vein was then punctured with a 16-gauge needle situated at the end of a closed, sterile blood-collection system containing citrate-phosphate-dextrose to inhibit coagulation. The blood was allowed to drain by gravity flow into the blood-collection bag, which was left hanging down. When the blood flow ceased, the needle was withdrawn from the umbilical vein, and the tubing system was double clipped for secure closure. The placenta was then delivered by spontaneous expulsion to minimize manual contamination11 or, if necessary, by manual removal. Conversely, in group B the placenta was first delivered as follows. Cord blood was collected from the delivered placenta after removal from the operative field. Briefly, the placenta was held up by an assistant, while the free end of the cord with the clamp in situ was straightened downward. The puncture and blood-harvesting procedure was performed within 5 minutes of placental delivery in the same way as described for group A. It is important that, as in group A, the collection procedure was terminated after the blood flow ceased and no placental manipulation was used to support blood flow. In both groups neither a second puncture nor other additional collection procedure were used. Assessment of cord blood samples. The volume of collected cord blood was determined by subtracting the volume of citrate phosphate dextrose from the total measured volume in the bag. Nucleated cell content was assessed with a Technicon H*3 RTC (Bayer Technicon),
and the total amount of nucleated cells per cord blood sample was calculated by multiplication with the cord blood volume contained in the bag. The fraction of CD34+ cells within the leukocyte population was determined by dual-color flow cytometry (fluorescence-activated cell sorting) with FACScan (Becton-Dickinson, San Jose, Calif). Briefly, whole cord blood was simultaneously stained with CD45–fluorescein isothiocyanate and CD34phycoerythrin (both from Becton-Dickinson). Red blood cell lysis was performed with Ortho-mune (Ortho Diagnostics) lysing reagent. The gating strategy consisted of a first gate (G1) of CD45+ intermediate to high forward scatter events (leukocyte gate) and a second gate (G2) of CD34+ high to low side-scatter events (CD34+ gate). The proportion of CD34+ cells among the leukocytes (nucleated cells) was calculated as the proportion of G1 within G2. The total amount of CD34+ cells per cord blood sample was calculated by multiplication of the relative CD34+ cell count with the total amount of leukocytes. Cell viability was determined by trypan blue extinction. Statistical analysis. Groups were compared regarding maternal, obstetric, and neonatal parameters. The primary outcome measure was the volume of cord blood obtainable. We calculated that a total study sample size of 40 would be required to detect a 30% difference in collectable cord blood volume between groups with a power of 80% at a significance level of .05. For statistical analysis, the groups were compared by the χ2 test or the Fisher exact test for categoric variables and the Mann-Whitney U test for continuous variables. A two-sided P < .05 was considered to be significant. Calculations were performed with SPSS 6.1 for Windows (SPSS Inc, Chicago, Ill) statistical software package. Results A total of 40 patients were randomized to group A (collection before placental expulsion, n = 21) or group B (collection after placental separation, n = 19) and were available for final analysis. Maternal and neonatal characteristics are summarized in Table I. There were no statistically significant differences between group A and group B concerning demographic characteristics and neonatal outcome. A larger volume of cord blood and a higher number of nucleated cells could be harvested in group A as opposed to group B (Table II). There was also a trend for a higher number of CD34+ cells, although the difference did not reach statistical significance (P = .076). The estimated blood loss during cesarean delivery and the measured prepartum versus postpartum maternal hemoglobin difference were slightly larger in group A; however, the difference was not statistically significant and the magnitude of the mean difference (37 mL and 0.1 g%, respectively) was unlikely to be clinically significant. The comparison of the operation time needed for
220 Surbek et al
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Table I. Maternal and neonatal characteristics
Maternal age (y) Primiparous women Elective cesarean delivery Gestational age (wk) Birth weight (g) Male neonatal sex Apgar score <8 at 5 min Cord pH (arterial) Cord pH (venous)
Group A (n = 21)
Group B (n = 19)
Statistical significance*
34 ± 1.1 10 (48%) 18 (86%) 39 ± 0.3 3400 ± 111 13 (62%) 0 7.27 ± 0.01 7.35 ± 0.01
32 ± 1.5 10 (52%) 14 (74%) 40 ± 0.3 3220 ± 90 10 (53%) 0 7.27 ± 0.01 7.34 ± 0.01
P = .254 P = .752 P = .442 P = .234 P = .401 P = .554 P = .831 P = .647
Cord blood collection before (group A) or after (group B) placental delivery. Data are given as mean ± SEM or number and percentages as indicated. *Mann-Whitney U test, χ2 test, or Fisher exact test was used where appropriate.
Table II. Cord blood data and maternal outcome
Cord blood volume (mL) Cord blood volume (mL/kg neonatal weight) Cord blood nucleated cells (×108) Cord blood CD34+ cells (×105) Relative CD34+ cell number (%) Maternal blood loss (mL) Difference in prepartum vs postpartum hemoglobin (g/dL)
Group A (n = 21)
Group B (n = 19)
Statistical significance*
93 ± 7.5 27 ± 1.9 11.1 ± 1.2 30.0 ± 6.0 0.29 ± 0.03 590 ± 27 1.4 ± 0.2
66 ± 6.6 20 ± 1.8 7.4 ± 0.8 17.4 ± 2.4 0.25 ± 0.03 553 ± 32 1.3 ± 0.4
P = .013† P = .011† P = .026† P = .076 P = .364 P = .115 P = .957
Cord blood collection before (group A) or after (group B) placental delivery. Data are given as mean ± SEM. *Mann-Whitney U test. †Statistically significant.
cesarean delivery (52 ± 6 vs 45 ± 2 minutes; P = .762) and the puerperal infection rate (P = 1) showed no difference between the 2 groups. Comment This randomized study shows that the amount of cord blood volume and the nucleated cell number obtainable by a single umbilical vein puncture during cesarean delivery is higher if the blood is collected with the placenta in utero compared with collection from the delivered placenta. This is possible without a significant negative effect on maternal blood loss, operation time, or puerperal infection rate. Other studies have assessed the influence of mode of delivery on cord blood collections.7,12 Both reports included vaginal and cesarean deliveries and were not randomized; the cord blood collection during cesarean delivery was performed after placental delivery. In the first study12 the mean cord blood volume and nucleated cell recovery after cesarean delivery were 65 mL and 7 × 108 cells, respectively (n = 20). In the other study7 a mean volume of 62 mL was collected (n = 82). In our study similar values resulted if the collection was performed after placental delivery. However, if the cord blood was obtained directly during cesarean delivery before placental delivery, a 30% to 50% increase in volume, nucleated cell
number, and even CD34+ cell number resulted. As a surrogate marker for hematopoietic progenitor-stem cells, CD34 is correlated with outcome after stem cell transplantation.13 A comparison with data obtained from vaginal deliveries published by our group previously10 shows that the cord blood yield was similar at vaginal birth (83 ± 7.9 mL or 25 ± 2.2 mL/kg birth weight) and cesarean delivery (93 ± 7.5 mL or 27 ± 1.9 mL/kg) if the collection was performed with the placenta in situ. These recovery values compare favorably with published data from cord blood banks for unrelated stem cell transplantations, where samples with cord blood values below a certain volume or nucleated cell count threshold were not included.14-16 The difference between the groups in our trial is likely to be clinically significant; it is known that the success of cord blood transplantation depends on the number of nucleated cells transplanted3, 4 and that the amount of cells in a cord blood sample is limited and often not enough for larger adolescent or adult recipients.17 The amount of fetal blood remaining in the placenta and the umbilical cord after clamping and dissection of the cord depends on birth weight, placental weight, and timing of cord clamping.18 Early clamping leads to increased placental blood volume, and late clamping favors a greater transfer of blood from the placenta to the fetus. This correlation has also been shown for cesarean deliv-
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eries with differences in placental transfusion, even within 40 seconds.19 The timing of cord clamping has been debated theoretically in the past. Early clamping might avoid extensive placental transfusion to the newborn, thus decreasing polycythemia, hyperbilirubinemia, and hypervolemia.20 Late clamping might avoid newborn anemia and has been shown to be advantageous in preterm infants.21 With the introduction of cord blood collection for allogeneic stem cell transplantation, this issue has gained new actuality. Concern has been raised about possible risks for the newborn involved in cord blood collection for stem cell transplantation at birth if the cord is clamped early for increased collection volume.22 Modifying the timing of cord clamping for unrelated cord blood banking does not appear to be justified; the situation needs discussion in case of selected targeted intrafamilial collection. Other means to increase cord blood yield include multiple punctures, flushing,23 or placenta manipulation. These procedures could be used in addition to a first simple puncture, as performed in our study. However, these techniques might increase the risk of bacterial, viral, or maternal blood cell contamination and could therefore be harmful for the recipient of the transplant through infection or graft-versus-host disease by maternal alloreactive lymphocytes. Another maneuver, consisting of placing the newborn on the maternal abdomen, has been reported recently24 but can obviously only be performed after a vaginal delivery. In conclusion, our data suggest that if a cesarean delivery has to be performed for obstetric reasons, it is beneficial to collect cord blood while the placenta is still in utero. This procedure might be preferably used for unrelated cord blood banking and especially if cord blood is collected for transplantation in an affected sibling.
6.
7.
8.
9.
10.
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13. 14.
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18. 19.
REFERENCES
1. Wagner JE, Kernan NA, Steinbuch M, Broxmeyer HE, Gluckman E. Allogeneic sibling umbilical-cord-blood transplantation in children with malignant and non-malignant disease. Lancet 1995;346:214-9. 2. Kurtzberg J, Laughlin M, Graham ML, Smith C, Olson JF, Halperin EC, et al. Placental blood as a source of hematopoietic stem cells for transplantation into unrelated recipients. N Engl J Med 1996;335:157-66. 3. Gluckman E, Rocha V, Boyer-Chammard A, Locatelli F, Arcese W, Pasquini R, et al. Outcome of cord-blood transplantation from related and unrelated donors. N Engl J Med 1997;337:373-81. 4. Rubinstein P, Carrier C, Scaradavou A, Kurtzberg J, Adamson J, Migliacco AR, et al. Outcomes among 562 recipients of placental-blood transplants from unrelated donors. N Engl J Med 1998;339:1565-77. 5. McCullough J, Clay ME, Fautsch S, Noreen H, Segall M, Perry E,
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et al. Proposed policies and procedures for the establishment of a cord blood bank. Blood Cells 1994;20:609-26. Harris DT, Schumacher MJ, Rychlik S, Booth A, Acevedo A, Rubinstein P, et al. Collection, separation and cryopreservation of umbilical cord blood for use in transplantation. Bone Marrow Transplant 1994;13:135-43. Bertolini F, Lazzari L, Lauri E, Corsini C, Castelli C, Gorini F, et al. Comparative study of different procedures for the collection and banking of umbilical cord blood. J Hematother 1995;4: 29-36. Rubinstein P, Dobrila L, Rosenfield RE, Adamson JW, Migliacco G, Migliacco AR, et al. Processing and cryopreservation of placental/umbilical cord blood for unrelated bone marrow reconstitution. Proc Natl Acad Sci U S A 1995;92:10119-22. Bertolini F, Battaglia M, Zibera C, Baroni G, Soro V, Perotti C, et al. A new method for placental/cord blood processing in the collection bag. I. Analysis of factors involved in red blood cell removal. Bone Marrow Transplant 1996;18:783-6. Surbek DV, Schönfeld B, Tichelli A, Gratwohl A, Holzgreve W. Optimizing umbilical cord blood mononuclear cell yield for haematopoietic stem cell transplantation: a randomized comparison of collection before vs. after placenta delivery. Bone Marrow Transplant 1998;22:311-2. Atkinson MW, Owen J, Wren A, Hauth JC. The effect of manual removal of the placenta on post-cesarean endometritis. Obstet Gynecol 1996;87:99-102. Screnci M, De Felice L, Carmini D, Picardi A, Arcese W. Does the type of delivery influence umbilical cord blood recovery? Bone Marrow Transplant 1995;16:631-4. Krause DS. CD34: structure, biology and clinical utility. Blood 1996;87:1-13. Dal Cortivo L, Marolleau JP, Gluckman E, Chavinié J, Brossard Y, Benbunan M. The Paris cord blood bank. Bone Marrow Transplant 1998;22(Suppl 1):S11. Navarrete C, Warwick R, Armitage S, Fehily D, Contreras M. The London cord blood bank. Bone Marrow Transplant 1998; 22(Suppl 1):S6-7. Querol S, Gabarró M, Amat L, Gonzalez M, Gomez MD, de la Calle O, et al. The placental blood program of the Barcelona cord blood bank. Bone Marrow Transplant 1998;22(Suppl 1):S3-5. Cairo MS, Wagner JE. Placental and/or umbilical cord blood: an alternative source of hematopoietic stem cells for transplantation. Blood 1997;90:4665-78. Yao AC, Moinian M, Lind J. Distribution of blood between infant and placenta after birth. Lancet 1969;2:871-3. Ogata ES, Kitterman JA, Kleinberg F, Dong L, Willis M, Mates J, et al. The effect of time of cord clamping and maternal blood pressure on placental transfusion with cesarean section. Am J Obstet Gynecol 1977;128:197-200. Peltonen T. Placental transfusion—advantage and disadvantage. Eur J Pediatr 1981;137:141-6. Kinmond S, Aitchison TC, Holland BM, Jones JG, Turner TL, Wardrop CAJ. Umbilical cord clamping and preterm infants: a randomised trial. BMJ 1993;306:172-5. Bertolini F, Battaglia M, De Iulio C, Sirchia G, Rosti L. Placental blood collection: effects on newborns. Blood 1995;85:3361-2. Turner CW, Luzins J, Hutcheson C. A modified harvest technique for cord blood hematopoietic stem cells. Bone Marrow Transplant 1992;10:89-91. Grisaru D, Deutsch V, Pick M, Fait G, Lessing JB, Dollberg S, et al. Placing the newborn on the maternal abdomen after delivery increases the volume and CD34+ cell content in the umbilical cord blood collected: an old maneuver with new applications. Am J Obstet Gynecol 1999;180:1240-3.
Key words: Umbilical cord blood, hematopoietic stem cells, cesarean delivery, cord blood collection
Umbilical cord blood is increasingly used as an alternative source of hematopoietic stem cells for related1 and unrelated2 allogeneic transplantation in children and adolescents. Recent data show that clinical outcome of cord blood transplantation is influenced by the number of nucleated cells transplanted.3, 4 Therefore the yield of stem cells remains an important aim of cord blood collection in addition to donor (ie, maternal and neonatal) safety. The strategy of cord blood collection varies between different cord blood banks.5 Open systems, which were initially used for cord blood retrieval,6 have been replaced by closed systems with blood-collection bags to minimize the risk of contamination with bacteria or maternal cells.7 Some authors described cord blood collecFrom the Department of Obstetrics and Gynecology,a the Laboratory of Hematology, Department of Central Laboratories,b and the Division of Hematology, Department of Internal Medicine,c University of Basel. Received for publication July 29, 1999; revised December 2, 1999; accepted January 12, 2000. Reprint requests: Daniel V. Surbek, MD, Harris Birthright Research Centre for Fetal Medicine, King’s College Hospital, Denmark Hill, London, United Kingdom SE5 9RS. Copyright © 2000 by Mosby, Inc. 0002-9378/2000 $12.00 + 0 6/1/105744 doi:10.1067/mob.2000.105744
218
tion at vaginal delivery after expulsion of the placenta,8 whereas others perform the collection while the placenta is still in utero9 or use a combination of the two.6 In a randomized trial we previously showed that cord blood collection during vaginal delivery is improved if performed before placental expulsion.10 If a cesarean delivery is performed for obstetric reasons, an optimal collection technique is also essential, especially if cord blood transplantation in a sibling is planned. There are, however, no prospective data about different cord blood-collection methods during cesarean delivery available to date. The aim of our study was to assess, in a randomized trial, whether cord blood collection before delivery of the placenta during cesarean delivery is superior to sampling from the delivered placenta by using a single umbilical vein puncture and a closed blood-collection system. Methods Study design. Pregnant women undergoing cesarean delivery at the Department of Obstetrics and Gynecology of the University Hospital of Basel were considered for inclusion into the study. Criteria for inclusion were singleton pregnancy, elective or secondary cesarean delivery, and willingness to participate in the study. Exclusion cri-
Surbek et al 219
Volume 183, Number 1 Am J Obstet Gynecol
teria were nonreassuring fetal heart rate, placenta previa, preterm birth, fetal growth restriction, maternal anemia with a hemoglobin level of <10 g/dL, and clinical chorioamnionitis. Informed consent was obtained from every subject before inclusion in the study. The study was approved by the institutional review board of the University Hospital. After inclusion and before cesarean delivery, women were randomized to group A (cord blood collection before placental delivery) or group B (cord blood collection after placental delivery) by means of random allocation of sealed opaque envelopes. Cord blood collection. Preoperative and postoperative management was according to standard protocol. Cesarean delivery was performed routinely by means of a low transverse uterine incision. After delivery of the newborn, the umbilical cord was double clamped and transected within 10 seconds, which is the standard procedure in our department. As soon as the newborn was removed from the operative field, 10 units of oxytocin was given intravenously. An umbilical cord fragment of 3 to 5 cm in length was obtained to assess arterial and venous cord blood acid-base status. Then in group A cord blood was collected as follows. The placenta-side part of the umbilical cord was held straight at a slight angle downward. After identification of a suitable puncture site, the umbilical cord was cleaned and disinfected with alcoholic polyvinylpyrrolidone-iodine solution. The umbilical vein was then punctured with a 16-gauge needle situated at the end of a closed, sterile blood-collection system containing citrate-phosphate-dextrose to inhibit coagulation. The blood was allowed to drain by gravity flow into the blood-collection bag, which was left hanging down. When the blood flow ceased, the needle was withdrawn from the umbilical vein, and the tubing system was double clipped for secure closure. The placenta was then delivered by spontaneous expulsion to minimize manual contamination11 or, if necessary, by manual removal. Conversely, in group B the placenta was first delivered as follows. Cord blood was collected from the delivered placenta after removal from the operative field. Briefly, the placenta was held up by an assistant, while the free end of the cord with the clamp in situ was straightened downward. The puncture and blood-harvesting procedure was performed within 5 minutes of placental delivery in the same way as described for group A. It is important that, as in group A, the collection procedure was terminated after the blood flow ceased and no placental manipulation was used to support blood flow. In both groups neither a second puncture nor other additional collection procedure were used. Assessment of cord blood samples. The volume of collected cord blood was determined by subtracting the volume of citrate phosphate dextrose from the total measured volume in the bag. Nucleated cell content was assessed with a Technicon H*3 RTC (Bayer Technicon),
and the total amount of nucleated cells per cord blood sample was calculated by multiplication with the cord blood volume contained in the bag. The fraction of CD34+ cells within the leukocyte population was determined by dual-color flow cytometry (fluorescence-activated cell sorting) with FACScan (Becton-Dickinson, San Jose, Calif). Briefly, whole cord blood was simultaneously stained with CD45–fluorescein isothiocyanate and CD34phycoerythrin (both from Becton-Dickinson). Red blood cell lysis was performed with Ortho-mune (Ortho Diagnostics) lysing reagent. The gating strategy consisted of a first gate (G1) of CD45+ intermediate to high forward scatter events (leukocyte gate) and a second gate (G2) of CD34+ high to low side-scatter events (CD34+ gate). The proportion of CD34+ cells among the leukocytes (nucleated cells) was calculated as the proportion of G1 within G2. The total amount of CD34+ cells per cord blood sample was calculated by multiplication of the relative CD34+ cell count with the total amount of leukocytes. Cell viability was determined by trypan blue extinction. Statistical analysis. Groups were compared regarding maternal, obstetric, and neonatal parameters. The primary outcome measure was the volume of cord blood obtainable. We calculated that a total study sample size of 40 would be required to detect a 30% difference in collectable cord blood volume between groups with a power of 80% at a significance level of .05. For statistical analysis, the groups were compared by the χ2 test or the Fisher exact test for categoric variables and the Mann-Whitney U test for continuous variables. A two-sided P < .05 was considered to be significant. Calculations were performed with SPSS 6.1 for Windows (SPSS Inc, Chicago, Ill) statistical software package. Results A total of 40 patients were randomized to group A (collection before placental expulsion, n = 21) or group B (collection after placental separation, n = 19) and were available for final analysis. Maternal and neonatal characteristics are summarized in Table I. There were no statistically significant differences between group A and group B concerning demographic characteristics and neonatal outcome. A larger volume of cord blood and a higher number of nucleated cells could be harvested in group A as opposed to group B (Table II). There was also a trend for a higher number of CD34+ cells, although the difference did not reach statistical significance (P = .076). The estimated blood loss during cesarean delivery and the measured prepartum versus postpartum maternal hemoglobin difference were slightly larger in group A; however, the difference was not statistically significant and the magnitude of the mean difference (37 mL and 0.1 g%, respectively) was unlikely to be clinically significant. The comparison of the operation time needed for
220 Surbek et al
July 2000 Am J Obstet Gynecol
Table I. Maternal and neonatal characteristics
Maternal age (y) Primiparous women Elective cesarean delivery Gestational age (wk) Birth weight (g) Male neonatal sex Apgar score <8 at 5 min Cord pH (arterial) Cord pH (venous)
Group A (n = 21)
Group B (n = 19)
Statistical significance*
34 ± 1.1 10 (48%) 18 (86%) 39 ± 0.3 3400 ± 111 13 (62%) 0 7.27 ± 0.01 7.35 ± 0.01
32 ± 1.5 10 (52%) 14 (74%) 40 ± 0.3 3220 ± 90 10 (53%) 0 7.27 ± 0.01 7.34 ± 0.01
P = .254 P = .752 P = .442 P = .234 P = .401 P = .554 P = .831 P = .647
Cord blood collection before (group A) or after (group B) placental delivery. Data are given as mean ± SEM or number and percentages as indicated. *Mann-Whitney U test, χ2 test, or Fisher exact test was used where appropriate.
Table II. Cord blood data and maternal outcome
Cord blood volume (mL) Cord blood volume (mL/kg neonatal weight) Cord blood nucleated cells (×108) Cord blood CD34+ cells (×105) Relative CD34+ cell number (%) Maternal blood loss (mL) Difference in prepartum vs postpartum hemoglobin (g/dL)
Group A (n = 21)
Group B (n = 19)
Statistical significance*
93 ± 7.5 27 ± 1.9 11.1 ± 1.2 30.0 ± 6.0 0.29 ± 0.03 590 ± 27 1.4 ± 0.2
66 ± 6.6 20 ± 1.8 7.4 ± 0.8 17.4 ± 2.4 0.25 ± 0.03 553 ± 32 1.3 ± 0.4
P = .013† P = .011† P = .026† P = .076 P = .364 P = .115 P = .957
Cord blood collection before (group A) or after (group B) placental delivery. Data are given as mean ± SEM. *Mann-Whitney U test. †Statistically significant.
cesarean delivery (52 ± 6 vs 45 ± 2 minutes; P = .762) and the puerperal infection rate (P = 1) showed no difference between the 2 groups. Comment This randomized study shows that the amount of cord blood volume and the nucleated cell number obtainable by a single umbilical vein puncture during cesarean delivery is higher if the blood is collected with the placenta in utero compared with collection from the delivered placenta. This is possible without a significant negative effect on maternal blood loss, operation time, or puerperal infection rate. Other studies have assessed the influence of mode of delivery on cord blood collections.7,12 Both reports included vaginal and cesarean deliveries and were not randomized; the cord blood collection during cesarean delivery was performed after placental delivery. In the first study12 the mean cord blood volume and nucleated cell recovery after cesarean delivery were 65 mL and 7 × 108 cells, respectively (n = 20). In the other study7 a mean volume of 62 mL was collected (n = 82). In our study similar values resulted if the collection was performed after placental delivery. However, if the cord blood was obtained directly during cesarean delivery before placental delivery, a 30% to 50% increase in volume, nucleated cell
number, and even CD34+ cell number resulted. As a surrogate marker for hematopoietic progenitor-stem cells, CD34 is correlated with outcome after stem cell transplantation.13 A comparison with data obtained from vaginal deliveries published by our group previously10 shows that the cord blood yield was similar at vaginal birth (83 ± 7.9 mL or 25 ± 2.2 mL/kg birth weight) and cesarean delivery (93 ± 7.5 mL or 27 ± 1.9 mL/kg) if the collection was performed with the placenta in situ. These recovery values compare favorably with published data from cord blood banks for unrelated stem cell transplantations, where samples with cord blood values below a certain volume or nucleated cell count threshold were not included.14-16 The difference between the groups in our trial is likely to be clinically significant; it is known that the success of cord blood transplantation depends on the number of nucleated cells transplanted3, 4 and that the amount of cells in a cord blood sample is limited and often not enough for larger adolescent or adult recipients.17 The amount of fetal blood remaining in the placenta and the umbilical cord after clamping and dissection of the cord depends on birth weight, placental weight, and timing of cord clamping.18 Early clamping leads to increased placental blood volume, and late clamping favors a greater transfer of blood from the placenta to the fetus. This correlation has also been shown for cesarean deliv-
Surbek et al 221
Volume 183, Number 1 Am J Obstet Gynecol
eries with differences in placental transfusion, even within 40 seconds.19 The timing of cord clamping has been debated theoretically in the past. Early clamping might avoid extensive placental transfusion to the newborn, thus decreasing polycythemia, hyperbilirubinemia, and hypervolemia.20 Late clamping might avoid newborn anemia and has been shown to be advantageous in preterm infants.21 With the introduction of cord blood collection for allogeneic stem cell transplantation, this issue has gained new actuality. Concern has been raised about possible risks for the newborn involved in cord blood collection for stem cell transplantation at birth if the cord is clamped early for increased collection volume.22 Modifying the timing of cord clamping for unrelated cord blood banking does not appear to be justified; the situation needs discussion in case of selected targeted intrafamilial collection. Other means to increase cord blood yield include multiple punctures, flushing,23 or placenta manipulation. These procedures could be used in addition to a first simple puncture, as performed in our study. However, these techniques might increase the risk of bacterial, viral, or maternal blood cell contamination and could therefore be harmful for the recipient of the transplant through infection or graft-versus-host disease by maternal alloreactive lymphocytes. Another maneuver, consisting of placing the newborn on the maternal abdomen, has been reported recently24 but can obviously only be performed after a vaginal delivery. In conclusion, our data suggest that if a cesarean delivery has to be performed for obstetric reasons, it is beneficial to collect cord blood while the placenta is still in utero. This procedure might be preferably used for unrelated cord blood banking and especially if cord blood is collected for transplantation in an affected sibling.
6.
7.
8.
9.
10.
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