1.Prenatal diagnosis of mitochondrial disease: analysis of 28 pedigrees with mitochondrial DNA mutation
Yu LIU ; Ying ZHANG ; Xuefei ZHENG ; Hong PAN ; Yu QI ; Yinan MA
Chinese Journal of Perinatal Medicine 2017;20(9):679-683
Objective To perform a prenatal diagnosis for the second fetuses from 28 pedigrees with proband of mitochondrial disease due to mitochondrial DNA (mtDNA) mutation.Methods From April 2011 to November 2015,peripheral blood samples of 28 probands and their parents,urine samples of these probands and their mothers as well as amniotic fluid samples of the second fetuses from the 28 pedigrees were collected in Peking University First Hospital.DNA sequencing was used to identify mtDNA mutations.Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was performed to verify mutation sites,calculate mutation loads,and further confirm the diagnosis after birth.Microsatellite maker analysis was also performed on five short tandem repeats located in nuclear genes to exclude maternal contamination.Statistical analysis was carried out using independent t-test.Results In the 15 pedigrees carrying A3243G mutation,13 mothers and nine fetuses carried A3243G mutation.Neither the other two mothers nor their fetuses were positive for A3243G mutation.Among the 12 pedigrees with T8993G mutation,there were eight mothers carrying T8993G mutation and all of their fetuses carried the same mutation;and the other four mothers and their fetuses were negative for T8993G mutation.T10191C mutation was only found in one proband and the second fetus of that pedigree,but not in the mother.None of the fathers had mtDNA mutation.Results of PCR-RFLP were consistent with those of DNA sequencing.Short tandem repeat analysis demonstrated that amniocyte samples were from fetuses without maternal contamination.No mtDNA mutations were found in the six newborns who were negative for mtDNA mutations in prenatal diagnosis.The mean mutation load in urine samples of the six mothers without A3243G mutation in amniocytes was significantly lower than that of the nine mothers with A3243G mutation [(10.1 ±4.8) % vs (28.2 ± 15.1) %,t=2.290,P=0.043].Conclusions The lower the mtDNA mutation load in maternal urine samples,the less the possibility she bears a child with mtDNA mutation.However,prenatal diagnosis of mitochondrial disease is necessary.
2.Clinical manifestations and prenatal diagnosis of congenital muscular dystrophy
Yanbin FAN ; Xiaona FU ; Lin GE ; Hui JIAO ; Haipo YANG ; Dandan TAN ; Aijie LIU ; Shujuan SONG ; Yinan MA ; Hong PAN ; Huixia YANG ; Jingmin WANG ; Hui XIONG
Chinese Journal of Perinatal Medicine 2017;20(9):669-678
Objective To summarize the clinical features of 22 probands diagnosed with congenital muscular dystrophy (CMD),and to provide genetic counseling and prenatal diagnosis for 23 fetuses of these pedigrees.Methods Data of 22 CMD patients who were treated in the Pediatric Department of Peking University First Hospital during October 2006 to March 2016 were analyzed.Informed written consents for participation in this study were obtained from the parents or guardians.Prenatal diagnosis was performed using DNA samples extracted from fetal villus cells of 12 cases at 11-13 gestational weeks and amniotic fluid of 11 cases at 18-22 gestational weeks.Direct DNA sequencing by polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA) were used to detect CMD-related gene mutations.Linkage analysis of short tandem repeats (STRs) was used to identify maternal blood contamination and biological parents.Results Thirteen out of the 22 probands with CMD were diagnosed with congenital muscular dystrophy type 1 A (MDC1A),and all of them carried compound heterozygous mutations in LAMA2 gene.Prenatal diagnosis of 13 fetuses from these pedigrees found that four fetuses were wild-type,seven were heterozygotes and two carried the same mutations as their proband.Three probands with LMNA-related congenital muscular dystrophy (L-CMD) carried de novo mutations in LMNA gene.In these pedigrees,two fetuses were wild-type and one whose mother was mosaicism carried the same mutations as the proband.One proband with Ullrich congenital muscular dystrophy carried compound heterozygous mutations in COL6A2 gene and the fetus of the same pedigree was wild-type.Five probands were diagnosed with α-dystroglycanopathies.And among them,two cases of muscle-eye-brain disease (MEB) carried compound heterozygous mutations in POMGnT1 gene and the fetuses of the two peidgrees were heterozygotes;one case of congenital muscular dystrophy type 1C (MDC1C) had compound heterozygous mutations in FKRP gene and the fetus carried the same mutations;one patient diagnosed with POMGnT1-related congenital muscular dystrophy with mental retardation (CMD-MR) carried compound heterozygous mutations in POMGnT1 gene,and the fetus was positive for the same mutations;one proband with POMT1-related CMD-MR was positive for compound heterozygous mutations in POMT1 gene and the results of prenatal diagnosis for two fetuses of this pedigree showed that the first fetus had the same mutations as the proband,while the second was heterozygote.Conclusions No effective therapeutic method is available for CMD.Therefore,accurate genetic counseling and prenatal diagnosis are necessary to prevent CMD child from birth.
3.Effect and safety of intraoperative cell salvage during cesarean section
Qian LI ; Yuyan NIE ; Guiqi GENG ; Shaoqiang HUANG ; Xiaotian LI
Chinese Journal of Perinatal Medicine 2017;20(9):656-660
Objective To assess the safety and effect of intraoperative cell salvage (ICS) during cesarean section.Methods This was a case-control study in which 60 gravidas who received ICS (ICS group) and 60 gravidas who received allogenic transfusion (control group) during caesarean section in Obstetrics and Gynecology Hospital of Fudan University during January 2014 to December 2016 were enrolled.Subjects in the two groups were matched in age,gestational age,gestational complications (placenta increta,placenta previa,scarred uterine,leiomyomas and anemia) and hemorrhagic volume during cesarean section.Several indicators including complications of transfusion,postoperative recovery,expense of transfusion,as well as the complete blood count and body temperature before and after operation were compared between the two groups.T,rank-sum or Chi-square test was used for statistical analysis.Results (1) No significant difference in age,gestational age,twin gestation,complications,preoperative body temperature,or the volume of hemorrhage or transfusion was observed between the two groups (all P>0.05).(2) The autotransfusion volume was 385 (161-583) ml in the ICS group.Fifteen cases (20.0%) in the ICS group also received additional transfusions of leukocyte-reduced red blood cell (RBC) suspension,fresh frozen plasma and cryoprecipitate and two cases (3.3%) received additional transfusions of leukocyte reduced RBC suspension and fresh frozen plasma.The two groups showed no significant difference in the cost of transfusion or per-capita transfusion volume of fresh frozen plasma or cryoprecipitate.However,the transfusion volume of leukocyte-reduced RBC suspension was lower in the ICS group as compared with that in the control group [M(P25-P75),1.9 (1.5-4.5) vs 4.1 (2.8-6.2) U,Z=-2.800,P=0.005].(3) There was no significant difference in complete blood count or coagulation function between the two groups before the operation.White blood cell (WBC) counts in the two groups were elevated following operation.Postoperative WBC count in the control group was higher than that in the ICS group,while the levels of RBC and hemoglobin were lower than those in the ICS group following operation (all P<0.05).(4) No amniotic fluid embolism was reported in the two groups.Only one case of rash was reported in the ICS group,which was fewer than the transfusion reactions occurred in the control group [1.7% (1/60) vs 13.3% (8/60),x2=5.886,P=0.016].(5) The two groups showed no significant difference in preoperative temperature,the highest temperature within three days after operation or incision healing.Compared with the patients in the control group,those in the ICS group had shorter hospital stay [(4.7± 1.1) vs (6.3 ±1.8) d,t=3.341,P<0.05].Conclusion ICS is a safe and effective measure for gravidas at higher risk of hemorrhage during cesarean section.
4.Associated factors and pregnancy outcomes of trial of labor after cesarean: a prospective cohort study
Suhua WEI ; Xiaodong YE ; Lili QIU ; Yimin DAI ; Zhiqun WANG ; Jie LI ; Aiyuan YUE ; Feiran ZHANG ; Mingming ZHENG
Chinese Journal of Perinatal Medicine 2017;20(9):649-655
Objective To investigate the safety of trial of labor after cesarean (TOLAC) and clinical factors associated with successful TOLAC and to compare TOLAC with elective repeat caesarean section (ERCS) in terms of obstetric and neonatal outcomes.Methods A prospective cohort study was conducted among gravidas who had a history of lower segment cesarean section and were hospitalized in the Department of Obstetrics and Gynecology,the Affiliated Drum Tower Hospital of Medical School of Nanjing University from January to December 2014.Exclusion criteria included indications for caesarean section (such as placenta previa,placenta accreta,twin pregnancy,breech presentation and severe preeclampsia),serious maternal complications after cesarean section,lower uterine segment thinner than 3 mm and poor healing of uterine incision.Totally,287 gravidas were enrolled.Among them,142 chose TOLAC and the other 145 requested ERCS.Clinical data of those gravidas were collected and statistically analyzed by t-test,Log-rank test,Chi-square or Fisher's exact test.Results (1) The success rate of TOLAC was 90.8% (129/142).There was no significant difference in maternal age,gestational age,thickness of lower uterine segment,interval between the two deliveries and neonatal birth weight and asphyxia rate between the successful (n=129) and unsuccessful (n=13) groups (all P>0.05).Although the two groups had no significant difference in postpartum hemorrhage (PPH) rate,the gravidas who failed in TOLAC lost more blood than those who succeeded [425 (195-675) vs 200 (50-1 400) ml,P<0.05].Moreover,higher amniotic fluid contamination rate was observed in the unsuccessful group [6/13 vs 17.1% (22/129),P<0.05].In the TOLAC group,99.3% (141/142) were under continuous fetal heart rate monitoring.Incomplete uterine rupture occurred in one women without serious maternal or neonatal outcomes.The reasons for 13 failed TOLAC cases were unbearable pain during labor,abnormal labor,fetal distress and threatened rupture of uterus.(2) Compared with the ERCS group,the TOLAC group showed shorter interval from last cesarean section to the indexed delivery[5 (2-18) vs 6 (2-19) years],younger maternal age [(31±4) vs (33 ±4) years old] and less blood loss [200 (50-1 400) vs 300 (100-1 500) ml] (all P<0.05).Conclusion Our study shows that,those who preferred TOLAC were younger,or had shorter pregnancy interval from last cesarean section.The success rate of TOLAC is high for women undergoing systematic prenatal assessment and close management during labor with less blood loss and non-serious maternal and neonatal complications compared with ERCS.
5.Efficacy of uteroplasty aided with temporary balloon occlusion of abdominal aorta in management of pernicious placenta previa combined with placenta percreta
Xianlan ZHAO ; Yingying DU ; Lei ZHAO ; Zhuan LIU ; Cai LIU ; Yan ZHOU ; Huixia YANG
Chinese Journal of Perinatal Medicine 2017;20(9):644-648
Objective To investigate the therapeutic effect of uteroplasty aided with temporary balloon occlusion of abdominal aorta in treating pernicious placenta previa combined with placenta percreta.Methods Sixty-two third-trimester gravidas who were diagnosed as pernicious placenta previa combined with placenta percreta by prenatal ultrasound and magnetic resonance imaging (MRI) in the First Affiliated Hospital of Zhengzhou University from January 1,2013 to May 31,2016 were enrolled in this study.All of them received cesarean section and then underwent uteroplasty following temporary balloon occlusion of abdominal aorta.Efficacy of that treatment was evaluated from the perspectives of blood loss,operation time,complications and postoperative recovery.All data were analyzed by descriptive analysis.Results All of the 62 cases were diagnosed with placenta percreta during operation including 10 cases (16.1%) with perimetrium invasion,46 cases (74.2%) with invasion to the muscular layer of bladder and six cases (9.7%) with bladder invasion.The average blood loss of all cases during and within 24 hours after operation was (1 377.3±605.2) ml and (140.6±66.3) ml,respectively.The average operation time was (72.3 ±24.5) min and the average length of postoperative hospital stay was (5.8± 1.6) d.The six cases of placenta percreta with bladder invasion received bladder repair.Sixty-one cases had their uterus preserved and the other one case had a sub-total hysterectomy due to amniotic fluid embolism.One woman developed phlebothrombosis in her lower limbs after operation.No intestinal or ureteral injury,puerperal infection,uterine ischemia necrosis or death was reported.In addition to three cases lost to follow-up,the other 59 patients were followed up to May 31,2017.Results of physical examination indicated that the 59 cases had normal uterine involution after operation.Menses returned in 58 of the 59 cases without any difference from before,and did not return in one case due to breastfeeding.Conclusion Uteroplasty aided with temporary balloon occlusion of abdominal aorta is a safe and effective uterus-preserving surgery for patients with pernicious placenta previa combined with placenta percreta.
6.Methicillin-resistant Staphylococcus aureus colonization in infants at neonatal intensive care unit and effect of mupirocin decolonization
Yumao HUANG ; Weimin JIN ; Wenna XIANG
Chinese Journal of Perinatal Medicine 2017;20(5):382-386
Objective To evaluate the methicillin-resistant Staphylococcus aureus (MRSA) colonization in infants at neonatal intensive care unit (NICU) by active surveillance cultures (ASC) and the effects of mupirocin decolonization on MRSA infection. Methods Neonates adimitted to NICU of Ruian People's Hospital of Zhejiang Province, China between October 1, 2013 and September 30, 2014 underwent ASC within 24 hours of admission (ASC group). The samples from nasal vestibule and umbilicus were cultured for MRSA, and positive cultures were considered as MRSA colonization. These with negative cultures underwent repeated culture of MRSA by ASC at the 1st and 2nd week after NICU admission. Neonates admitted to NICU between October 1, 2014 and September 30, 2015 with MRSA colonization based on ASC were decolonized with mupirocin at both nasal vestibule and umbilicus twice daily for five consecutive days (decolonization group). Culture samples were obtained one day and one week after decolonization to repeat ASC. ASC was stopped if the subsequent culture was negative twice successively; and a second mupirocin decolonizaton was performed if the culture was positive. Chi-square test was used to compare the rates of colonization and infection between the two groups. Results (1) MRSA colonization and infection in ASC group: MRSA colonization rates within 24 hours, and in the 1st and 2nd week after NICU admission in ASC group were 2.2% (9/418), 3.7% (15/402) and 3.6% (13/361), respectively. Compared with those without MRSA colonization, neonates with MRSA colonization had a higher incidence of MRSA infection [13.5% (5/37) vs 3.7% (14/381), χ2=7.524, P=0.006]. (2) MRSA colonization and infection in decolonization group: MRSA colonization rates within 24 hours, and at the 1st and 2nd week after NICU admission in decolonization group were 2.8% (12/435), 2.9% (12/414) and 1.3% (5/373), respectively. The MRSA colonization rate at the 2nd week was significantly lower than that in ASC group (χ2=3.919, P=0.048). Twenty-nine cases had MRSA colonization, among which, 27 cases were decolonized once and two cases were decolonized twice, and all were successful. The rate of MRSA infection in decolonization group was 2.1% (9/435), which was significantly lower than in ASC group [4.5% (19/418)] (χ2=4.118, P=0.042). Conclusions Rate of MRSA colonization is high at NICU. Mupirocin can decolonize MRSA carriage and reduce MRSA infection in neonates.
7.Associations of polymorphisms of cytochrome P450 enzymes (CYP2D6 and CYP2C9) with early-onset severe pre-eclampsia and labetalol therapy
Chengjuan SUN ; Yike YANG ; Weiyuan ZHANG ; Xiaowei LIU
Chinese Journal of Perinatal Medicine 2017;20(5):375-381
Objective To explore the associations of the genetic polymorphisms of cytochrome P450, family 2, subfamily D, polypeptide 6 (CYP2D6) and cytochrome P450, family 2, subfamily C, polypeptide 9 (CYP2C9) with early-onset severe pre-eclampsia and the efficacy of labetalol therapy. Methods Totally 105 gravidas diagnosed with early-onset severe pre-eclampsia (experimental group) and 103 healthy gravidas (control group) were recruited from Beijing Obstetrics and Gynecology Hospital between August 2013 and July 2016. Labetalol was given to control blood pressures in gravidas with early-onset severe pre-eclampsia. If labetalol administration alone did not exceed the mean dose (100 mg, one dose per eight hours) and effectively controlled the blood pressures, it would be considered to be valid (n=75), otherwise it would be viewed as an invalid treatment. Genotype and allele frequencies of CYP2C9 gene (rs1057910 and rs4918758) and CYP2D6 gene (rs1065852, rs28371725, rs35742686 and rs3892097) in the gravidas were analyzed by TaqMan probe polymerase chain reaction. Differences in the genotype and allele frequencies were compared between the experimental and control groups, and the valid and invalid labetalol treatment groups. Chi-square test, analysis of variance and LSD test were used as statistical methods. Results The gravidas in both experimental and control groups were AA genotype in CYP2C9 gene rs1057910, TT genotype in CYP2D6 gene rs35742686 and CC genotype in CYP2D6 gene rs3892097. Frequencies of CC and CT genotypes in CYP2D6 gene rs28371725 in the experimental group were higher than those in the control group [18.1% (19/105) vs 14.6% (15/103);56.2% (59/105) vs 42.7% (44/103); χ2=6.707], and higher C allele frequency in CYP2D6 gene rs28371725 was also observed in the experimental group [46.2% (97/210) vs 35.9% (74/206), χ2=4.529] (all P<0.05). No statistical differences in maternal age, diastolic pressure, body mass index before pregnancy, serum triglyceride, creatinine and neonatal birth weight were observed among women with CC, CT or TT genotype of CYP2D6 gene rs28371725 in the experimental group (all P>0.05). Compared with the gravidas with CT or TT genotype of CYP2D6 gene rs28371725, those with CC genotype had longer gestational age [(32.5±2.1) vs (29.5±1.8) and (29.8±2.2) weeks] and higher plasma albumin [(27.2±9.3) vs (20.3±10.4) and (22.5±7.4) g/L], but lower systolic pressure and 24 hours urine protein (LSD test, all P<0.05). The G allele frequency in CYP2D6 gene rs1065852 in invalid labetalol treatment group was higher than that in valid labetalol treatment group [93.3% (56/60) vs 76.0% (114/150), χ2=8.351, P=0.004]. Conclusions The polymorphism of CYP2D6 gene rs28371725 may be associated with early-onset severe pre-eclampsia, and the allele of G in CYP2D6 gene rs1065852 may be associated with the efficacy of labetalol in treatment of early-onset severe pre-eclampsia.
8.Postoperative outcomes of twin-twin transfusion syndrome complicated with selective intrauterine growth restriction
Xueju WANG ; Luyao LI ; Yuan WEI ; Pengbo YUAN ; Yangyu ZHAO
Chinese Journal of Perinatal Medicine 2017;20(5):371-374
Objective To evaluate the efficacy of fetoscopic laser occlusion of chorioangiopagous vessels (FLOC) in treatment of twin-twin transfusion syndrome (TTTS) and to investigate the incidence of TTTS complicated with selective intrauterine growth restriction (sIUGR) for better understanding the effects of sIUGR as a complication of TTTS on pregnancy outcomes. Methods A retrospective study was performed on 116 gravidas who were diagnosed with TTTS of Quintero stage Ⅰ - Ⅳ in Peking University Third Hospital from September 2008 to September 2014. Among them, 44 cases received FLOC therapy. The incidences of sIUGR in each Quintero stage of TTTS were analyzed. Pregnancy outcomes of those 44 cases treated with FLOC were observed and the differences among four stage groups were analyzed. Chi-square or Fisher exact test was performed for statistical analysis. Results (1) The survival rates of both twins from stage Ⅰ to Ⅳ groups were 4/7, 10/14, 5/19 and 3/4, respectively, with statistically significant difference (χ2=7.840, P=0.038), but that in stage Ⅲ group was lower than in stage Ⅱ group without significant difference (P'=0.008). Differences in the total fetal survival rate among the four groups were statistically significant [8/14, 75% (21/28), 32% (12/38) and 6/8, χ2=14.016, P=0.002]. The total fetal survival rate in stage Ⅲ group was significantly lower than that in stageⅡ group (P'<0.008). In patients with stage Ⅲ TTTS, those complicated with sIUGR, after receiving FLOC therapy, showed a lower total fetal survival rate than those without sIUGR [21% (6/28) vs 6/10, P<0.05]. (2) Among the 116 TTTS patients, there were 63 cases (54%) with sIUGR complication. Patients with sIUGR complication in TTTS stages Ⅰ to Ⅳ groups accounted for 40% (14/35), 48% (11/23), 78% (28/36) and 46% (10/22), respectively, and the differences were significant (χ2=11.963,P=0.007). The incidence of sIUGR in stage Ⅲ group was greater than that in stage Ⅰ group (χ2=10.482, P'=0.002), and those in both stage Ⅲ and Ⅱ groups were higher than in stage Ⅰgroup without significant difference. Conclusions TTTS patients in stage Ⅲ have lower survival rate of both twins and total fetal survival rates after FLOC therapy, which may be related to a higher incidence of concurrent sIUGR.
9.Analysis of eight cases with perinatal pulmonary embolism
Na LIU ; Yan LONG ; Li LIN ; Jie MENG
Chinese Journal of Perinatal Medicine 2017;20(8):618-622
Objective To analyze the incidence,risk factors,clinical characteristics and pregnant outcomes of perinatal pulmonary embolism(PPE).Methods Clinical data of eight patients who were admitted to Beijing Friendship Hospital of Capital Medical University for PPE from January 2006 to March 2016 were collected.General condition,symptoms,laboratory examinations,images,treatments and outcomes of these patients were analyzed retrospectively.Results The ten-year incidence of PPE was 0.029% (8/27 560) in this hospital.Among the eight cases,two cases were diagnosed in the first trimester,and treated successfully by thrombolytic therapy.But one of two cases stopped growth,while the other one was premature labor.There were one case in the third trimester who had successful anticoagulant therapy and five cases in the postpartum period after cesarean delivery.Among the five cases,three cases were recovered after anticoagulant therapy,one case was recovered after thrombolytic therapy and one case died.All of the eight patients were immobilized before the onset of PPE,and five of them were diagnosed after cesarean section.Four out of the eight patients were obese.Five patients had three or more high-risk factors for pulmonary embolism and the other three had two.Conclusions It is necessary to pay close attention to gravidas who have two or more high-risk factors of PPE due to its fatal outcome.
10.Bordetella pertussis infection in infants less than three months: analysis of 59 cases from 2011 to 2015 in a single center
Xiaoying WANG ; Rong MI ; Jin FU ; Li LI ; Xiaodai CUI ; Baoyuan ZHANG ; Hong ZHU ; Jun HE ; Yanwei LI
Chinese Journal of Perinatal Medicine 2017;20(8):583-588
Objective To study the epidemiological and clinical characteristics ofpertussis in infants younger than three months.Methods Infants younger than three months were enrolled from January 1,2011 to December 31,2015 with one or more of the following symptoms:persistent cough,spasmic cough,cyanosis of unknown causes,asphyxia and apnea.Multiplex polymerase chain reaction(PCR) assay was performed to identify Bordetella pertussis and enzyme-linked immunosorbent assay was used to detect antibody to pertussis toxin.Clinical features,complications,treatments and prognosis of the infants confirmed with pertussis were analyzed.Results Altogether 202 cases were enrolled in the five years,and 59 (29.2%) of which were positive for pertussis confirmed by multiplex PCR.Among the 59 cases,37 were boys and 22 were girls.The youngest baby was 13 days and the oldest one was 85 days.Length of stay ranged from 7 to 21 days.Twelve cases had a contact history with family members having chronic cough.Symptoms occurred in spring or summer in 46 cases (78.0%),and in autumn or winter in 13 (22.0%) cases.Symptoms of spasmic cough,cyanosis after coughing,vomiting after coughing and conjunctival hemorrhage were respectively found in 41 (69.5%),36 (61.0%),39 (66.1%)and 33 (55.9%) cases,while only six (10.2%) presented with inspiratory whooping sound on coughing.Fortynine cases (83.1%) showed increased lymphocyte count (≥ 10 × 109/L).Twenty-eight cases (47.5%) developed severe pertussis.Complications including apnea and bradycardia after coughing,respiratory failure and heart failure,pertussis encephalopathy as well as highly increased leucocyte count (≥ 60× 109/L) occurred in 23 (39.0%),18 (30.5%),five (8.5%) and four (6.8%) cases,respectively.Twenty-four cases with severe pertussis required respiratory support,of which six received invasive ventilation and 18 received non-invasive ventilation.Fifty-eight infants were recovered and discharged,while one baby died.Conclusions Bordetella pertussis infection is an important cause of persistent cough in unimmunized infants under three months of age.The symptoms of pertussis in infants are untypical,but the incidence of severe pertussis is high.Thus early diagnosis and timely treatment are necessary.