Surgical site infections following pediatric liver transplantation: risks and costs.

PURPOSE: Infectious complications following orthotopic liver transplantation (OLT) represent a significant cause of morbidity and mortality in both adults and children. In adults, surgical site infections complicating OLT have been shown to significantly increase resource utilization, but their impact in children has not been studied. In this study we identify risk factors for surgical site infections in children undergoing primary OLT for end-stage liver disease and estimate their impact on patient survival, graft survival, length of stay, and charges. METHODS: All pediatric liver transplants (n = 77) less than 16 years of age from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Liver Transplantation Database were included in the analysis. Surgical site infections (n = 25) were defined as wound infections, abdominal abscesses, and bacterial or fungal infections of the liver, intestine, or peritoneum during the initial transplant admission. Risk of infection was estimated using logistic regression, survival rates were estimated using the Kaplan-Meier method, and length of stay and charges were compared using Student's t-test. Multivariate analysis of charges was performed using linear regression. RESULTS: Of the 77 patients, 25 (32.5%) developed a surgical site infection. Several factors were associated with increased risk of infections, including a leak at the biliary anastomosis (odds ratio [OR] 115, P = 0.003), preoperative white blood cell count (OR = 1.28, P = 0.009), surgery > 7 h (OR = 15.0, P = 0.011), HLA mismatches (OR = 6.0, P = 0.03), and female gender (OR = 8.0, P = 0.038). Surgical site infections did not significantly decrease either patient survival or graft survival, and increased hospital stay by an average of 21 days (P = 0.14). After controlling for other factors, patients who developed surgical site infections incurred on average $132,507 (P = 0.03) more in charges than patients who did not develop infections. CONCLUSIONS: Surgical site infections in pediatric patients following liver transplantation are significantly influenced by surgical technique and endogenous patient characteristics. Though survival outcomes are not different, the development of such infections has significant implications for resource utilization in the care of these patients.

Immunosuppression as adjuvant therapy for biliary atresia.

BACKGROUND/PURPOSE: Despite improvements in the surgical management of biliary atresia, the long-term incidence of progressive liver failure remains high. Because chronic inflammation involving both bile ducts and liver parenchyma contributes to the pathology, the authors have hypothesized that the liver damage may be altered using immunosuppressive therapy. The aim of this study was to examine the safety and efficacy of long-term steroid therapy in patients with biliary atresia. METHODS: A retrospective analysis of all patients with biliary atresia treated with an hepatoportoenterostomy and postoperative steroid therapy at our 3 institutions was undertaken. Patients were treated uniformly with immunosuppressive doses of oral steroids for a minimum of 6 weeks after surgery. RESULTS: Twenty-five infants with biliary atresia were treated with steroid therapy. Overall survival rate was 22 patients (88%) with a mean follow-up period of 50 months. Nineteen patients (76%) became jaundice free with native liver function. Four patients (16%) did not respond to treatment and required transplantation. Age less than 12 weeks was a crucial predictor of success of adjuvant steroid therapy. Cholangitis developed in 8 patients (32%). There were no complications caused by steroid therapy. CONCLUSIONS: Steroid administration at immunosuppressive doses markedly improves the clinical outcome within the first 5 years after surgery as measured by jaundice-free status and survival without liver transplantation when compared with concurrent reports. These results suggest that immunosuppressive therapy is safe and has a positive impact on the clinical course of this disease. However, a randomized study is needed to ultimately prove such an hypothesis.

Postnatal pulmonary hypertension after repair of congenital diaphragmatic hernia: predicting risk and outcome.

BACKGROUND: Pulmonary hypertension (PH) after congenital diaphragmatic hernia (CDH) repair remains a significant cause of morbidity and mortality. Although treatment advances have improved overall survival, a new cohort of patients is surviving with PH beyond the postnatal period. Because the clinical entity of postnatal persistent pulmonary hypertension (PPHTN) in CDH patients has not been published, the authors undertook a retrospective study of our neonatal CDH experience to characterize this group of infants. METHODS: Charts of all infants with CDH treated at this institution from January 1991 to June 1997 were reviewed (n = 51). Persistent pulmonary hypertension by echocardiographic (Echo) measurements at the time of discharge identified PPHTN patients. Control survivors had normal pulmonary artery pressures at discharge. Physiological parameters and the results of therapeutic interventions were analyzed to predict PPHTN. RESULTS: Seven infants (four boys, three girls) had PPHTN at discharge. Significant differences with the control group were noted in length of stay, duration of intubation, and duration of nitric oxide therapy. Extracorporeal membrane oxygenation (ECMO) duration was not significantly different between the groups. By 12 months of age, PPHTN resolved in six patients (87%), and one died at 13 months. Regardless of therapy, two parameters showed 100% positive predictive value for identifying patients with PPHTN (P < .001): an Echo demonstrating PH at 2 months of age or continued oxygen requirement at 3 months. Oxygen requirement at 2 months had a 67% predictive value of PPHTN. CONCLUSIONS: With current treatment strategies for CDH, infants can survive with persistent pulmonary hypertension beyond the newborn period. The long-term survival rate is excellent, and normalization of pulmonary artery pressures can be expected. PPHTN can be predicted in those infants with Echo-defined pulmonary hypertension at 2 months.

Challenge of supportive surgical care in pediatric oncology.

The advent of aggressive treatment protocols and the development of new techniques and procedures now require that the pediatric surgeon be an integral part of all aspects of pediatric oncology care. Supportive care issues, rather than primary tumor management decisions, now dominate the pediatric surgeon's experience and range from managing the different types of vascular access devices and their complications to assessing the surgical implications of the toxic complications of current chemotherapy protocols. New treatments such as bone marrow transplantation have presented new challenges to the pediatric surgeon, while new techniques such as minimally invasive surgery have dramatically improved our ability to render compassionate and more effective care to our patients as they undergo these potentially toxic treatment regimens.

Soluble ICAM-1 (sICAM-1) in biliary atresia and its relationship to disease activity.

BACKGROUND: Intercellular adhesion molecule-1 (ICAM-1) is strongly expressed on the bile ducts and hepatic parenchyma of livers with biliary atresia. A soluble, circulating form of this membrane protein has been found to be elevated in a number of inflammatory hepatic disorders. However, its expression in biliary atresia is unknown. The purpose of this study was to assess the presence of soluble ICAM-1 in infants with biliary atresia in relation to disease activity, degree of cholestasis, and standard liver function tests. MATERIALS AND METHODS: A total of nine patients (n = 9) with biliary atresia (seven) and neonatal hyperbilirubinemia (two) were studied (age range 6 weeks-9 years). Control samples were obtained from three healthy infants (2-10 months). Serum was collected from each patient and stored at -80 degrees C until assayed. Levels of sICAM-1 were measured in duplicate utilizing an ELISA method (Bioscource International). Standard liver function tests (conjugated bilirubin, gamma-glutamyl transpeptidase, alkaline phosphatase, alanine aminotransferase) were determined at the same time. Results are expressed as the means +/- SEM with statistical analysis by Mann-Whitney test. RESULTS: sICAM-1 levels were significantly elevated in all patients with biliary atresia (997 +/- 56 ng/ml) when compared to controls (P < 0.001). No correlation was found between sICAM-1 levels and conjugated bilirubin, gamma-glutamyl transpeptidase, alkaline phosphatase, and alanine aminotransferase levels or with clinical assessment of disease severity. CONCLUSIONS: sICAM-1 is markedly elevated in biliary atresia reflecting the immunopathology of the disease process but does not appear to correlate with markers of liver function. sICAM-1 may be useful in assessing the effects of immunomodulatory therapy.

Bayer Immuno 1 PSA Assay: an automated, ultrasensitive method to quantitate total PSA in serum.

The Bayer Immuno 1 PSA Assay measures total PSA in human serum and demonstrates excellent performance with an interassay CV < or = 3.4% and a biological detection limit of 0.03 microgram/L. No significant interference from common hormonal and chemotherapeutic drugs, kallikrein, prostatic acid phosphatase, and trypsin, or elevated levels of total bilirubin, hemoglobin, triglycerides, and IgG was observed. The 95th percentile values for healthy individuals increased with age from 3.0 micrograms/L for males 50-59 years and 3.3 micrograms/L for males 60-69 years, to 4.6 micrograms/L for males > or = 70 years. Clinical studies with retrospective samples demonstrated correspondence between serial measurements of PSA and clinical outcome for 98% of 159 prostate cancer patients. Clinical sensitivity for patients with clinical evidence of disease, untreated at the time of specimen draw, increased with increasing stage from 77.5-100%. Specificity of 60-70% for BPH and other benign urogenital diseases was consistent with previous findings. Bayer Immuno 1 PSA Assay values for 2131 specimens from healthy subjects and patients with prostate cancer, BPH, and other malignant and nonmalignant diseases correlated well with the Abbott IMx PSA Assay over the range 0.0-6,238 micrograms/L (Y = 1.10 x + 0.02). The Bayer Immuno 1 PSA Assay provides automated ultrasensitive, precise, and equimolar measurement of total PSA in human serum.

Long-term outcome for infants and children with sacrococcygeal teratoma: a report from the Childrens Cancer Group.

BACKGROUND/PURPOSE: Sacrococcygeal teratomas (SCT) are a relatively uncommon tumor affecting neonates, infants, and children. This study was designed to determine the effect of therapy on the long-term outcome of neonates and children with sacrococcygeal teratomas (SCT). METHODS: The authors conducted a retrospective review of children with SCT treated at 15 Childrens Cancer Group institutions from 1972 to 1994. RESULTS: One hundred twenty-six children presented with SCT diagnosed prenatally (n = 32), at birth (n = 79), or later in infancy (n = 15). For neonates, complete resection was performed except in two babies with lethal associated defects. All others (n = 15) underwent resection at the age of diagnosis. Six had a sacral mass identified at birth but had delayed surgery (1.5 to 11 months) and of these, two were malignant. Resection was via sacral (n = 96) or abdominosacral (n = 28) approach. Histology showed mature teratoma (MT, 69%), immature teratoma (IT, 20%), or endodermal sinus tumor (EST, 11%) at presentation. Seven neonates (5.6%) died of perioperative complications, whereas the remaining 117 were available for long-term follow-up. Between 6 and 34 months postresection, recurrent disease developed in 9 of 80 MT patients (11%) followed-up for a mean of 5 years. Recurrent disease was MT (n = 2) and EST (n = 7). The recurrent EST patients were treated with adjuvant chemotherapy. Six are alive with mean follow-up of 114 months, whereas one with metastatic disease was lost to follow-up. Recurrence (MT) developed in only 1 of 24 IT patients, and all are alive and well at mean follow-up of 39 months. Patients presenting with EST (n = 13) underwent excision, with two dying from non-EST causes. Six EST patients received no chemotherapy, with two of the six (33%) experiencing recurrence within 11 months and both disease free after salvage chemotherapy. The remaining five EST patients received adjuvant chemotherapy; four are alive and one died of metastatic disease. Of the 18 EST patients followed-up after resection (presentation, 11, recurrent teratoma, 7), 16 (89%) are free of disease with a mean follow-up of 91 months. CONCLUSIONS: (1) Benign teratomas have a significant recurrence rate mandating close follow-up for more than 3 years. (2) Surgical resection alone is adequate therapy for nonmetastatic malignant tumors. (3) Survival for malignant lesions with metastases is excellent with modern chemotherapy.

Advances in neonatal care and surgery.

Neonatology has seen many advances over the past decade. Exogenous surfactant therapy is now a mainstay treatment for respiratory distress syndrome. Partial liquid ventilation, high-frequency ventilation, and inhaled nitric oxide are all relatively new modalities, which have enabled neonatologists to treat with varying degrees of success ever younger and smaller patients. The purpose of this review is to examine studies regarding the long-term outcome of high-risk neonates, the various treatment modalities, and current neonatal surgical techniques, all of which will influence our care of the neonate.

Analytical performance of Bayer Immuno 1 estradiol and progesterone assays.

We evaluated the analytical performance of new estradiol and progesterone assays performed on the Bayer Immuno 1 system. Within-run and between-day CVs for estradiol at concentrations of 116.8-6645.8 pmol/L were < or = 6.4% and for 5.54-103.95 nmol/L progesterone were < or = 7.7%, thus meeting published analytical goals. The detection limits (2 SDs from mean of zero calibrator) were 27.1 pmol/L for estradiol (n = 72 over 20 days) and 0.51 nmol/L for progesterone (n = 47 over 20 days). The assays were linear to 9766 pmol/L and 113.0 nmol/L, respectively. Estradiol results agreed well with the Diagnostic Products Corporation (DPC) assays, except for serum samples from patients receiving estrogen replacement therapy; results for these samples agreed closely with the DPC estradiol-6 assay. The progesterone assay agreed closely with the DPC assay, except for samples from uremic patients. Reference values were estimated by the study of 29 women throughout the menstrual cycle with 15 samples per subject. We concluded that both assays demonstrate suitable precision, linearity, and intermethod agreement to allow their use in the clinical laboratory.

Regenerative healing of incisional wounds in midgestational murine hearts in organ culture.

OBJECTIVE: Using an organ-culture fetal heart repair model, we explored fetal repair in tissues other than dermis. METHODS: Wounded fetal mouse hearts of 14 and 18 days' gestation (term = 20 days), as well as hearts of 22 days' gestation (newborn), were maintained in serum-free medium. Specimens were fixed at 2, 7, and 11 days and then processed for histologic examination. Small fragments of fetal hearts from all time points were cultured as explants. The migration of cells from the periphery of the explants was compared at day 4, and the pattern of microfilaments in these cells was assessed. RESULTS: In 14-day hearts (n = 18), tissue architecture was rapidly reestablished without an inflammatory response or scarring, constituting regenerative repair. In 18-day hearts (n = 18), no reestablishment of muscle fibers or wound closure occurred. In the 22-day explants (n = 12) the wounds closed by scarring. Cell migration from 14-day explants was 4.7 +/- 2.3 ocular units; from 18-day explants, it was 2.6 +/- 1.1 ocular units; and from 22-day explants, it was 0.9 +/- 0.4 ocular units. Microfilaments of 14-day cells were arranged at the periphery of the cell consistent with cardiomyocytes. Microfilaments of 18- and 22-day cells were arranged in parallel arrays (stress fibers) that were consistent with fibroblasts. CONCLUSIONS: We propose that regenerative healing of 14-day fetal hearts is by the migration of cardiomyocytes. At 18 and 22 days, cardiomyocytes are too differentiated and unable to migrate; hence cell migration is limited to resident fibroblasts, which are deficient at 18 days but sufficient at 21 days to be repaired by the scarring process.

Nonrhabdomyosarcoma soft tissue sarcomas in children.

Nonrhabdomyosarcoma soft tissue sarcomas are very rare tumors in the pediatric population and consist of a heterogeneous collection of subtypes. They can occur anywhere in the body, with the extremities the most common anatomic site. In the initial evaluation of a soft tissue mass, proper radiographic evaluation is best performed with magnetic resonance (MR) imaging, while tissue for diagnosis should be obtained with a well planned incisional biopsy. Complete surgical resection remains the cornerstone of therapy, but it is now recognized that multi-modal strategies incorporating surgery, radiotherapy, and chemotherapy should be studied for incompletely resected tumors and those with poor prognostic indicators.

Differential expression of the major histocompatibility antigens and ICAM-1 on bile duct epithelial cells in biliary atresia.

Aberrant expression on biliary epithelial cells of the major histocompatibility complex (MHC) antigens in association with adhesion molecule intercellular adhesion molecule-1 (ICAM-1) may be crucial to the immunopathogenesis of biliary atresia. The patterns of MHC class I and II expression in relation to ICAM-1 expression as well as the associated lymphocyte subpopulations were studied in frozen section liver biopsies from six infants with biliary atresia. Intense ICAM-1 expression was found on all ductal epithelial cells in association with MHC I. No ductal epithelial cells demonstrated MHC II expression. Lymphocyte populations within the portal tracts all expressed LFA-1 and were predominantly CD4 positive (> 70%). CD8 positive cells accounted for less than 30%. The expression of ICAM-1 appears to be important in the pathogenesis of biliary atresia but is not linked to the expression of MHC II determinants. This result suggests that different regulatory mechanisms govern the expression of these important immunological receptors on biliary epithelial cells.

Pediatric soft tissue infections.

Quite often a soft tissue infection in a child may be the primary reason for seeking medical attention or an incidental finding on examination. To identify those infections that may be serious and require further intervention, all those dedicated to the care of children must be familiar with these illnesses and their complications. This article covers selected bacterial, viral, and fungal infections of the skin, subcutaneous fat, fascia, and muscle. Special considerations for the immunosuppressed child will also be discussed.

Neonatal soft tissue sarcomas: the influence of pathology on treatment and survival. Children's Cancer Group Surgical Committee.

INTRODUCTION: A multi-institutional study was conducted by the Children's Cancer Group (CCG) to evaluate all soft tissue sarcomas diagnosed within the first month of life. METHODS: A retrospective study by 11 CCG institutions of patient records from 1971 to 1991 were reviewed for demographic data, pathology, therapy, and outcome. RESULTS: 32 neonates with soft tissue sarcomas were identified. There were 21 boys and 11 girls. Pathology was equally divided into three groups: Congenital fibrosarcoma (CFS) (12), rhabdomyosarcoma (RMS) (11), and non-RMS soft tissue sarcomas (NRSTS) (9). Anatomic sites consisted of head/neck (11), extremity (9), trunk (8), pelvis (3), and unknown (2). Overall survival rate was 59% (19/32). CONCLUSION: Soft tissue sarcomas in the neonate comprise three general groups with survival rates dependent on pathology and extent of disease.

Regenerative healing of incisional wounds in murine fetal lungs maintained in organ culture.

Although fetal dermal repair is known to be fundamentally different from adult healing, the response to wounding in other organs is less well characterized. Scarless repair in mid-gestation dermis with a transition to adult-type healing at term has been shown in fetal organ culture. A lung explant culture system was used to investigate whether wound repair in the fetal lung shows characteristics similar to those found in fetal dermis. Lungs from 14-day and 18-day Cd-1 murine fetuses and 2-day-old newborns, (term = 20 days, n = 24) were wounded by linear incision and incubated at 37 degrees C, in a 21% O2, 5% CO2 environment, in BGJb supplemented with vitamin C and antibiotics. Medium was changed daily. Samples were fixed at 7 days and embedded in paraffin. Sections were stained with hematoxalyn-eosin and Masson Trichrome. Additional 14-day and 18-day samples were frozen in freon and immunohistochemical staining for TGF-beta performed. Other frozen tissues from each time point were homogenized and used to assay for endogenous TGF-beta levels by Western blot analysis. Histology showed reconstitution of tissue architecture across the wound in 14-day and 18-day specimens. In representative histological sections, intact bronchial architecture developed across the previous wound site. No cellular inflammatory response was observed, and collagen deposition was undetectable at the site of the wound by Trichrome staining. By 22 days the lung explants showed a much less ordered repair, including disorganized collagen deposition.(ABSTRACT TRUNCATED AT 250 WORDS)

Minimally invasive surgery in children with cancer.

BACKGROUND: The safety and efficacy of minimally invasive oncologic procedures in children have not been well defined and only limited anecdotal experience has been published. METHODS: A retrospective review of all patients undergoing either a laparoscopic or thoracoscopic procedure at Childrens Cancer Group institutions between December 1, 1991, and October 1, 1993, was performed. RESULTS: Eighty-five children underwent 88 minimally invasive surgical procedures as part of the evaluation or treatment for cancer at 15 participating centers. In 25 patients, laparoscopy was performed and 60 patients underwent 63 thoracoscopic operations. Tissue biopsies were taken in 67 cases and diagnostic material was obtained in 99% of the biopsies. Seven complications occurred, all within the thoracoscopic group. These included conversion of six operations to an open procedure. One patient developed atelectasis postoperatively. CONCLUSIONS: In pediatric patients with suspected cancer, laparoscopy was highly accurate with minimal morbidity; thoracoscopy was nearly as efficient with slightly higher morbidity. Both modalities are useful for assessment of resectability, for staging purposes, and for evaluation of recurrent or metastatic disease.

Nitric oxide reversal of recurrent pulmonary hypertension and respiratory failure in an infant with CDH after successful ECMO therapy.

Nitric oxide (NO) represents a new therapeutic modality for treating neonatal pulmonary hypertension and may obviate the need for extracorporeal membrane oxygenation (ECMO) in a number of cases of neonatal respiratory failure. Recently, the authors treated an infant with a congenital diaphragmatic hernia and pulmonary hypertension with NO on two separate occassions. During the initial period of stabilization, NO failed to reverse the pulmonary hypertension and prevent the development of progressive respiratory failure. After a successful course of ECMO, recurrent pulmonary hypertension developed that was successfully treated with continuous low-dose NO therapy for over 1 month. Prolonged administration of NO in varying doses titrated to clinical and echocardiographic parameters was well tolerated by the infant and prevented the need for a second run of ECMO.

Diagnosis, management, and outcome of cervicofacial teratomas in neonates: a Childrens Cancer Group study.

The management of cervicofacial teratomas in neonates is often complicated and may result in significant morbidity and death. A Childrens Cancer Group (CCG) retrospective study was conducted to evaluate a multiinstitutional experience with the treatment of these extremely rare neoplasms. Twenty neonates with cervicofacial teratomas, presenting from 1971 to 1994, were identified from nine CCG institutions. Fourteen neonates had cervical teratomas, and six had orofacial teratomas. There were 12 males and eight females. A diagnostic prenatal ultrasound examination was performed in six cases. Life-threatening airway obstruction occurred in seven infants (35%) in the early postnatal period. Two neonates died in the delivery room without ever having their airway secured. Two other infants with a prenatal diagnosis survived only because tracheostomies were performed by pediatric surgeons who were in the delivery room. Three other patients were orally intubated, one after sustaining hypoxic cardiac arrest. Eighteen infants had their primary tumor excised. Three patients required tracheostomy. After resection, two patients had evidence of unilateral recurrent laryngeal nerve injury, and two required prolonged thyroid hormone replacement. Histological examination showed eight mature and seven immature teratomas. Four infants (20%) clearly had malignant lesions. Pulmonary metastases occurred in two patients and contributed to one late death at 6 months of age. The overall survival rate was 85%, and the mean follow-up period was 5 years (range, 2 months to 16 years). Twelve of 17 surviving patients (70%) have had an excellent functional and cosmetic outcome. Four children have varying degrees of developmental delay and mental retardation. Hypoxia at birth was believed to have contributed to these problems in two cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional quantitation of pediatric tumor bulk.

In pediatric oncology, therapeutic decisions are made based on tumor response to chemotherapeutic agents. Sequential measurement of tumor bulk and its percent change on therapy must be accurately assessed. Will 3-dimensional (3-D) volumetric determination improve our ability to assess tumor response to therapy? Forty-five CT scans of pediatric patients with unresectable thoracic or abdominal neoplasia were assessed for tumor bulk by the standard "2-dimensional (2-D)" volume formula (cross-sectional area x length) and by 3-D volumetric analysis. Thirty-two examinations were performed in follow-up, and percent change in tumor size was calculated. The 2-D volume calculation overestimated tumor volume by more than 50% on all but two examinations when the 2-D volume was compared with the 3-D volume. In 28% of follow-up examinations, the 2-D calculation of percent change differed by more than 10% from the 3-D volume. Fifteen percent differed by over 25%. This changed the response category of one patient from "no response" to "partial response". 3-D volumetric analysis, easily performed by a trained technologist, will give more accurate assessment of the actual tumor bulk and its subsequent changes in size in response to therapy.

The extracellular matrix of the fetal wound: hyaluronic acid controls lymphocyte adhesion.

Adhesive interactions between lymphocytes and components of the extracellular matrix (ECM) within a wound environment play a crucial role in determining the inflammatory response following tissue injury. In fetal wounds the extracellular matrix is composed predominantly of hyaluronic acid. Within this environment the inflammatory reaction as a result of injury is minimal. We propose that this lack of an inflammatory cell response in the fetal wound is due to the high levels of hyaluronic acid within the ECM and the inability of lymphocytes to adhere to this matrix component. Therefore, we examined the adhesive properties of fetal lymphocytes to fibronectin, vitronectin, collagen types I, III, IV, V, and hyaluronic acid--ECM components involved in fetal and adult wound environments. Fetal lymphocytes from both spleen and thymus demonstrated significant binding capabilities to fibronectin, vitronectin, and collagen types I and III. No intrinsic binding capabilities were detected to hyaluronic acid. Adhesion was not affected by the addition of IL-1, IFN-gamma, or phorbol dibutyrate. The inability of lymphocytes to adhere to hyaluronic acid helps to explain the lack of inflammation found in fetal wounds and serves to demonstrate the importance of ECM-lymphocyte interactions in determining the inflammatory response during fetal wound healing.