乙型肝炎病毒感染胎盘的免疫组织病理学研究

目的：分析胎儿乙型肝炎病毒（HBV）感染与胎盘感染的关系。探讨HBV通过胎盘屏障感染胎儿的机理,方法：采用聚合酶链反应及酶联免疫吸附试验,对61例HBV携带孕妇的新生儿脐血或静脉血行HBV DNA及HBsAg检测,证实有胎儿HBV感染的28例为胎儿感染组,无胎儿HBV感染的33例为对照组,对两组孕妇的胎盘行免疫组织病理学检查并作组织学分级,结果：（1）61例HBV携带孕妇的胎盘组织中,共发现HBsAg和（或）HBcAg阳性41例,阳性率为67％,其中胎儿感染组阳性23例,阳性率为83％,对照组阳性18例,阳性率为55％,两组比较,差异有显著性（P＜0．05）,（2）两组胎盘组织细胞成分比较显示,胎儿感染组羊膜细胞的HBsAg和（或）HBcAg阳性率为36％（10／28）,明显高于对照组的6％,两组比较,差异有极显著性（P＜0．01）,（3）在两组的胎盘屏障各层组织细胞中,合体细胞的HBsAg和（或）HBcAg阳性率（49％）最高,明显高于其他层次组织细胞的阳性率（P＜0．05）,（4）两组胎盘组织病理学比较显示,胎儿感染组纤维样坏死（＋＋＋）发生率为29％,绒毛血管增生或充血的发生率为50％,均分别高于对照组的9％,15％,而胎儿感染组Hofbauer细胞阳性率为46％,明显低于对照组的79％,两组比较,差异有显著性（P＜0．05）,结论：胎儿感染HBV与胎盘感染有关,胎盘组织中可出现纤维素样坏死及绒毛血管增生或充血增多,Hofbauer细胞减少等改变,羊膜细胞感染是胎儿宫内HBV感染的重要因素之一,胎盘屏障对胎儿有一定的保护作用。     

乙型肝炎病毒感染孕妇IL-18对Th1/Th2细胞免疫平衡的作用与胎儿宫内感染相关性研究

目的：探讨乙型肝炎病毒（HBV）感染孕妇外周血白细胞介素-18（IL-18）水平对11hl／Th2细胞免疫的平衡作用与胎儿宫内感染的相关性。方法：选择2006年1月至2006年10月在本院分娩孕产妇101例，合并HBV感染、肝功能正常，单胎、足月妊娠。检测新生儿脐血HBV-DNA及HBsAg，诊断胎儿宫内感染2l例为研究组，无宫内感染80例为对照组。用双抗夹心酶联免疫吸附法（DAS-ELISA）检测孕妇外周血清IL-18、IFN-1（γ-干扰素）、IL4的水平。结果：（1）研究组孕妇外周血IL-18及IFN-1明显低于对照组，而IL4水平明显高于对照组，两组差异有统计学意义（P〈0．05，P〈0．0l，P〈0．05）；研究组IFN-γ／IL-4比值较对照组明显降低，差异有统计学意义（P〈0．01）。（2）两组孕妇外周血IL-18与IFN-γ均呈显著正相关、与IL-4水平均呈显著负相关、与IFN-γ／IL-4比值均呈显著正相关。结论：HBV宫内感染与孕妇Thl型特异性反应降低以及Th2型特异性反应增强有关，Thl／Th2免疫平衡失调可能是胎儿HBV宫内感染的机制之一；HBV宫内感染与孕妇外周血IL-18分泌下降有关，IL-18水平下调可能是HBV宫内感染的危险因素之一。     

乙型肝炎病毒宫内感染相关因素的研究

目的探讨乙型肝炎病毒（HBV）宫内感染的相关因素、新生儿外周血单个核细胞（PBMC）及胎盘HBV感染的影响因素。方法分别采用酶联免疫吸附试验,检测151例血清HBsAg阳性孕妇HBV标志物及其新生儿血清HBsAg;PCR检测孕妇及其新生儿血清和PBMC中的HBV DNA;免疫组化ABC法检测孕妇胎盘组织中HBsAg。非条件logistic回归模型对孕妇血清HBV DNA阳性、孕妇PBMC HBV DNA阳性、胎盘HBV感染等73项危险因素进行分析。结果（1）151例血清HBsAg阳性孕妇分娩的151例新生儿中,血清HBsAg阳性5例,血清HBV DNA阳性29例,PBMC HBV DNA阳性36例,HBV标志物任一项阳性57例,宫内感染率为37．8％（57／151）。（2）HBV宫内感染的危险因素为孕妇血清HBV DNA阳性、孕妇PBMC HBV DNA阳性、胎盘HBV感染比值比（OR）分别为2．25（1．08～4．72）、2．69（1．26～5．73）、4．63（1．70～12．62）。（3）胎盘HBV感染的危险因素为孕妇血清HBV DNA阳性,OR为4．24（1．22—14．69）。（4）新生儿PBMC HBV DNA阳性的危险因素为孕妇PBMC HBV DNA阳性,OR为24．53（7．92～76．01）。结论孕妇PBMC和血清HBV DNA阳性及胎盘HBV感染为HBV官内感染的危险因素;孕妇PBMC HBV DNA阳性可能是形成新生儿宫内感染的独立危险因素。     

阻断乙型肝炎病毒母婴传播的临床研究

目的探讨乙型肝炎病毒(HBV)母婴传播的途径及阻断措施。方法对2002年6月至2003年6月广东省江门市妇幼保健院2568例孕妇孕期筛查HBV标志物HBVM，对}玎3sAg( )孕妇检测HBVDNA，并于妊娠16～20周每月注射乙型肝炎免疫球蛋白(HBIG)，采用择期剖宫产术终止妊娠，新生儿检测Ht3VM，并联合免疫注射HBIG及乙型肝炎疫苗，检测产妇乳汁HBVDNA，阳性者采用人工喂养婴儿。结果筛查孕妇2568例，HBsAg( )者318例，占12．38％。新生儿HBsAg( )者10例，占3．14％，新生儿1个月时复测无新增病例，多种措施联合阻断成功率达96．86％。结论孕妇早期检测HBVM、HBVDNA，早诊断，早治疗，多种措施干预，可有效阻断乙型肝炎病毒母婴传播。     

乙型肝炎病毒宫内感染机理的研究

目的　探讨乙型肝炎病毒 (HBV)宫内感染的可能机理。方法　应用PCR技术检测 5 9例乙型肝炎病毒表面抗原 (HBsAg)阳性孕妇的羊水、阴道分泌物及其新生儿脐血清中HBVDNA(研究组 ) ,10例乙型肝炎病毒标志物 (HBVM )阴性的正常孕妇及其新生儿为对照组。采用免疫组化ABC染色法检测两组孕妇胎盘组织中的HBsAg及乙型肝炎核心抗原 (HBcAg)的阳性率。 结果　 ( 1)研究组孕妇的羊水、阴道分泌物、新生儿脐血清中HBVDNA阳性率分别为 4 7 5 % ( 2 8/ 5 9)、5 2 5 % ( 31/5 9)、4 5 8% ( 2 7/ 5 9) ;对照组孕妇的羊水、阴道分泌物、新生儿脐血清中均未检出HBVDNA。 ( 2 )研究组孕妇胎盘组织中HBsAg及HBcAg的阳性率 ,呈现出由蜕膜细胞 ( 76 3%及 5 9 3% )、滋养层细胞 ( 72 9%及 5 5 9% )、绒毛间质细胞 ( 6 2 7%及 5 0 8% )至绒毛毛细血管内皮细胞 ( 5 2 5 %及 4 4 1% )依次递减的趋势 ;但其中有 4例孕妇胎盘组织中HBsAg及HBcAg的分布与上述特点相反。研究组孕妇有 32例羊膜细胞中检出HBsAg及HBcAg。对照组孕妇胎盘组织中的HBsAg及HBcAg检出率为零。结论　孕妇血中HBV主要是通过感染胎盘导致胎儿感染 ;但也可能存在胎盘以外的感染途径。     

孕期弓形体感染对胎、婴儿的影响及治疗

目的：研究孕期弓形体感染胎、婴儿的结局，母婴传播途径及治疗。方法：应用ＥＬＩＳＡＩｇＭ方法筛查３８７８例孕妇弓形体近期感染情况。追踪８２例弓形体近期感染孕妇分娩的胎、婴儿预后、收集脐血、羊水、胎盘及尸解的器官组织了解母婴传播途径及病理改变。观察应用螺旋霉素系统治疗孕期弓形体感染者的胎、婴儿预后，并与未治疗组对照。结果：本组孕妇弓形体近期感染发生率为４．４１％（１７１／３８７８），其胎、婴儿出现临床症状为３０．４８％（２５／８２）；孕早期感染以畸胎、流产多见，孕晚期感染表现为早产、低体重儿、黄疸及弓形体感染性肺炎等。从胎盘、羊水、脐血及尸解器官组织中可查出弓形体ＤＮＡ。显示弓形体可通过胎盘感染胎儿，严重者造成器官损害。应用螺旋霉素治疗孕期弓形体感染有效。治疗组先天性弓形体感染发生率低于对照组（Ｐ＜０．０１）。结论：孕妇近期弓形体感染可通过胎盘感染胎儿，造成畸胎、流产、早产、低体重儿及急性弓形体感染症状。螺旋霉素治疗孕期弓形体感染有效。     

乙肝病毒母婴垂直传播胎盘超微结构变化

目的　通过对乙肝病毒 (HBV)母婴垂直传播者胎盘超微结构的观察 ,探讨 HBV母婴垂直传播的细胞学机制。　方法　用 EL ISA双抗夹心法对孕妇静脉血及其胎儿脐血、新生儿静脉血进行 HBV检测。对 5例发生 HBV母婴垂直传播者胎盘用 JEM- 12 0 0 EM透射电镜观察超微结构变化。　结果　 HBV双抗原阳性孕妇 6 0 %发生 HBV母婴垂直传播。HBV母婴垂直传播胎盘的超微结构改变有 :胎盘合体细胞内核糖体增多 ,微绒毛增多、变形 ,合体细胞变性坏死 ;胎盘屏障中毛细血管基底膜增厚、纤维蛋白样物沉积 ,合体细胞间隙、胞浆、细胞核内见多种病毒样颗粒。　结论　 HBV可感染胎盘合体细胞并且在其中复制 ,从而使胎儿在宫内被感染。     

妊娠期肝炎病毒多重感染对母婴的影响

目的 探讨妊娠期肝炎病毒多重感染对母婴的影响。方法 对1994年1月至1999年12月在我院产前检查,肝功能异常的孕妇行甲、乙、丙、丁、戊等5种肝炎病毒标记物检测,其中确诊为肝炎病毒多重感染者32例（多重感染组）,确诊为肝炎病毒单一感染者32例（单一感染组）,对两组母儿并发症及预后进行观察比较。结果 两组丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）、血清总胆红素（TBIL）水平比较,差异无显著性（P＞0．05）。多重感染组乙型肝炎病毒e抗原（HBeAg)阳性率（35．7％）显著低于单一感染组（76．9％,P＜0．05）,而乙型肝炎病毒e抗体（HBeAb)阳性率（57．1％）显著高于单一感染组（15．4％,P＜0．01）。多重感染组孕妇妊娠高血压综合征（妊高征）、产后出血、重症肝炎、死亡的发生率与单一感染组比较,差异无显著性（P＞0．05）。而多重感染组胎膜早破、早产的发生率（28．1％,25．0％）明显高于单一感染组（6．3％、3．1％,P＜0．05）;胎儿宫内窘迫及新生儿窒息的发生率（31．3％,25．0％）显著高于单一感染组（9．4％、0．0％,P＜0．05、P＜0．01）。结论 妊娠期肝炎病毒多重感染对孕妇的影响无明显加重,而对围产儿的影响较为明显;应加强孕期保健,防止胎膜早破及早产的发生。     

胎儿生长受限胎盘病理改变与Fas／FasL的表达

目的 通过观察胎儿生长受限（FGR）者胎盘病理改变与胎盘组织中Fas／FasL的表达，探讨Fas／FasL在病理妊娠FGR中的作用。方法 选择孕龄为37～42周的单胎妊娠妇女，根据新生儿出生体重定为FGR30例，用HE组织染色观察胎盘绒毛滋养细胞增生与合体滋养细胞结节增生情况、绒毛间质纤维化及绒毛血管病变情况，用免疫组化技术检测胎盘组织中Fas及FasL的表达，并与相同孕龄及新生儿出生体重正常者30例（对照组）比较。结果FGR组胎盘有22例发生了明显的病理改变，发生率为73．3％，其中有绒毛间质纤维化及纤维素样坏死者为66．7％，有合体滋养细胞结节增生者为46．7％，有绒毛血管减少者为70．0％，有滋养细胞增生者为53．3％，明显高于对照组（P〈0．01）。在FGR组胎盘组织绒毛滋养细胞和蜕膜细胞中，Fas的表达强度明显强于对照组（P〈0．01），FasL的表达强度则明显弱于对照组（P〈0．01）。结论 FGR时胎盘发生了明显的病理改变，FGR者胎盘Fas的高表达、FasL的低表达使母一胎易发免疫排斥，致胎盘组织免疫病理损伤，导致FGR。     

孕妇及婴儿联合免疫阻断乙型肝炎病毒宫内传播的临床研究

目的　探讨母婴联合免疫阻断乙型肝炎病毒宫内传播的效果。　方法　将 2 16例乙肝表面抗原阳性孕妇分组 ,母婴联合组 12 6例 ,孕妇自孕 2 8周起注射人乙型肝炎免疫球蛋白 (HBIG)2 0 0IU ,新生儿于 0、15d各注射HBIG 2 0 0IU ,然后于 1、2、7月龄各接种基因乙肝疫苗 (HBVac )2 0 μg。对照组 90例 ,只对新生儿进行免疫。母儿血清检测采用美国Abbott酶联免疫试剂测定 ,随访1年。　结果　联合免疫组婴儿宫内感染率低于对照 ( 19.5 1%与 35 .5 6 % ) ,慢性HBV感染率由13.33%降为 3.97% ,P均 <0 .0 5 ;联合免疫组及对照组新生儿出生时抗HBs检出率 ( 80 .95 %与 0 )及 1岁时保护性抗体产生率 ( 96 .0 3%与 86 .6 7% )均明显高于对照组 ,P均 <0 .0 5。　结论　孕妇及婴儿联合免疫可有效预防宫内感染且明显提高宫内感染阻断效果 ,减少慢性HBV感染率     

乙型肝炎表面抗原与乙型肝炎e抗原阴性孕妇乙型肝炎病毒宫内感染的研究

目的 探讨应用套式PCR方法检测乙型肝炎表面抗原(HBsAg)及乙型肝炎e抗原(HBeAg)阴性孕妇乙型肝炎病毒(HBV)宫内感染的状况。方法 选择HBsAg与HBeAg阴性,其他HBV血清标志物阳性孕妇及其新生儿24例作为病例组,同期HBV血清标志物全部阴性孕妇及其新生儿16例作为对照组。采用套式PCR方法检测两组孕妇及其新生儿的血清及外周血单个核细胞(PBMC)中HBV-DNA。结果(1)病例组24例孕妇中,血清HBV-DNA阳性8例,阳性率为33％;PBMC中HBV-DNA阳性10例,阳性率为42％r。其中血清与PBMC均阳性3例,总阳性率为63％r(15／24)。(2)病例组24个新生儿中,血清HBV-DNA阳性3例,阳性率为13％,PBMC中HBV-DNA阳性6例,阳性率为25％。其中血清与PBMC均阳性1例,宫内感染率为33％(8／24)。(3)病例组24例孕妇中,血清阴性而PBMC阳性共7例,其新生儿4例发生宫内感染,感染率为4／7。(4)对照组16例孕妇及其新生儿血清及PBMC中HBV-DNA全部阴性。结论 HBsAg及HBeAg阴性孕妇也可发生HBV宫内感染,采用灵敏度高的套式PCR方法检测孕妇及其新生儿血清及PBMC中HBV-DNA,对诊断HBV宫内感染具有重要临床意义。     

用荧光探针定量PCR技术检测孕妇与胎儿乙肝病毒感染的研究

目的 :探讨孕妇血中乙肝病毒 (HBV)DNA数量与胎儿乙肝病毒感染的关系。方法 :对 71例孕妇乙肝病毒表面抗原 (HBsAg)阳性者 ,用荧光探针定量PCR(FQ -PCR)方法 ,检测血清、宫颈分泌物及乳汁中HBVDNA数量 ,HBVDNA阳性者肌注乙肝免疫球蛋白 ,分娩后新生儿取末梢静脉血进行HBVDNA定量测定。结果 :孕妇血中HBVDNA阳性者其宫内感染率为 32 .6 % ,宫内感染与孕妇血中HBVDNA数量有关 ,HBVDNA数量高易导致胎儿宫内感染 ,乙肝免疫球蛋白可阻断HBV宫内传播。结论 :FQ -PCR方法能快速、准确检测孕妇血中HBVDNA数量 ,孕妇血中HBVDNA数量高易导致胎儿宫内感染 ,孕期肌注乙肝免疫球蛋白可减少胎儿乙肝病毒感染     

Prevention of vertical hepatitis B transmission by hepatitis B immunoglobulin in the third trimester of pregnancy.

OBJECTIVE: To explore the possible efficacy of using hepatitis B immunoglobulin (HBIG) during the third trimester of pregnancy to prevent intrauterine transmission of hepatitis B virus (HBV). METHODS: Of 469 pregnant women testing positive for hepatitis B surface antigens (HBsAg), 126 had hepatitis B e antigen (HBeAg) and 343 did not. RESULTS: There were women who declined to be treated with HBIG in these 2 groups. Among infants born to HBeAg-positive mothers, the rates of those testing positive for HBsAg at birth and at the 6-month visit were significantly lower when the mothers had been treated with HBIG (P<0.05). Among infants born to HBeAg-negative mothers, however, no significant differences were found whether the mothers had been treated or not. Furthermore, all newborns received HBIG treatment and the first dose of a vaccination schedule within 12 h of birth. At the 6-month visit the protective anti-HBs rates were only 32.3% among infants whose mothers were HBeAg-positive and 56.2% among those whose mothers were HBeAg-negative when their mothers had not been treated with HBIG during pregnancy, whereas the corresponding rates were as high as 75.8% and 88.7% when the mothers had been treated. CONCLUSION: Maternal administration of HBIG is effective in preventing intrauterine fetal HBV infection in HBsAg-positive, HBeAg-positive pregnant women and in improving immune response to hepatitis B vaccine in infants born to HBV carriers.     

孕妇血清中乙型肝炎病毒DNA含量与胎儿宫内感染的关系

探讨孕妇血清中乙型肝炎病毒ＤＮＡ含量与胎儿宫内感染发生率的关系。方法用斑点杂交法检测１８５例乙型肝炎病毒表面抗原阳性孕妇血清中ＨＢＶＤＮＡ及新生儿ＨＢｓＡｇ。结论孕妇血清ＨＢＶＤＮＡ含量升高是胎儿发生乙型肝炎病毒感染重要因素之一。     

胎盘乙型肝炎病毒感染与宫内传播的关系

目的 探讨乙型肝炎病毒（ＨＢＶ）宫内传播的危险因素,并追踪ＨＢＶ经胎盘传播的途径和胎儿宫内感染的时间,方法 共收集了乙型肝炎表面抗原（ＨＢｓＡｇ）携带孕妇１３１例,其中孕早期人工流产胎盘２４例,孕中期引产胎盘和胎儿各６例,足月分娩胎盘和新生儿各１０１例。孕妇和新生儿血清ＨＢｓＡｇ和ＨＢＶ ＤＮＡ检测分别采用酶联免疫吸附试验和聚酶链反应法。     

Pattern of hepatitis virus infection among pregnant women and their newborns at the Women's Health Center of Assiut University, Upper Egypt

Objective

To determine the prevalence, risk factors, and rate of vertical transmission of HBV and/or HCV infection among pregnant women in Upper Egypt, and assess the preventive efficacy of administering hepatitis B immunoglobulin and vaccine to newborns on their carrier status at 8 months.

Methods

Five hundred pregnant women were screened for HCV and HBV serum markers by enzyme-linked immunoassay. Those testing positive had their status confirmed by polymerase chain reaction and their levels of liver enzymes and interferon gamma were evaluated. The newborns of HBV-positive women received hepatitis B immunoglobulin and vaccine and were followed up to assess the rates of vertical transmission and carrier status among the newborns.

Results

Of the 500 pregnant women, 6.4% were HCV positive, 4.0% were HBV positive, and 1.0% were both. The vertical transmission rate was 3.1% for HCV, 30.0% for HBV, and 20.0% for a combined infection. The carrier rate of the infants at the end of their eighth month was 10.8% for those with HCV and 8% for those with HBV.

Conclusion

Infection with HBV and/or HCV is highly prevalent among pregnant women in Upper Egypt. The rate of vertical transmission was also high. Administering hepatitis B vaccine and immunoglobulin resulted in a 92% reduction in carrier status among newborns.     

Risk of perinatal transmission of hepatitis B virus in Jordan

OBJECTIVES: To determine the risk of perinatal transmission of hepatitis B virus (HBV) in Jordan. METHODS: Plasma samples from 1000 pregnant Jordanian women were screened by ELISA for HBV markers (HBsAg, HBeAg, anti-HBe, anti-HBc and anti-HBs). RESULTS: HBsAg and HBeAg were detected in 4.3% and 0.1% of the pregnant women, respectively. The overall prevalence of antibodies was 6%, 11.1% and 7.5% for anti-HBe, anti-HBc and anti-HBs, respectively. Women were assigned to four groups according to the serological patterns of HBV markers: susceptible (85.9%), with acute infection (2.9%), with chronic infection (1.4%) and previously infected (9.8%). Most women were at the third trimester of pregnancy, therefore women with acute and chronic hepatitis at this gestational age were at risk of transmitting HBV infection to their newborns. Women who belonged to the low socio-economic class were at higher risk of HBV infection. CONCLUSIONS: Based on the results, we recommend screening women for HBV during pregnancy in order to identify HBV carriers. All newborns born to carriers should be vaccinated immediately after birth, both passively and actively. Also vaccination of HBV seronegative pregnant women is recommended.     

Hepatitis B vaccine in pregnancy: immunogenicity, safety and transfer of antibodies to infants

To determine the safety and immunogenicity of hepatitis B vaccine in pregnancy, 72 pregnant Nigerians who were negative for markers of hepatitis B virus (HBV) were given two intramuscular doses of vaccine (Heptavax, Merck) in the third trimester. One month after the second dose (at T2), 84% were anti HBs positive. No significant effect was observed in the mothers or their newborns. Passive transfer of anti HBs occurred in 59% of the newborns. The antibodies disappeared rapidly in these infants and by 3 months only 23% had detectable antibodies. No HBsAg carrier status developed in this group. In contrast, the infants born to HbsAg positive mothers had a cummulative rate of HBV events of 20%. It is concluded that HBV vaccine is safe and immunogenic in pregnant females. The passive immunity conferred on the infants is of short duration. Therefore, infants in endemic areas should be vaccinated early, preferably within 3 months of birth. Vaccination of pregnant mothers may provide adequate protection before the child is vaccinated.     

Role of peripheral blood mononuclear cell transportation from mother to baby in HBV intrauterine infection

Purpose

We aimed to investigate the role of peripheral blood mononuclear cell transportation from mother to baby in hepatitis B virus (HBV) intrauterine infection.

Methods

Thirty HBsAg-positive pregnant women in the second trimester and their aborted fetuses were included in this study. Enzyme-linked-immunosorbent-assay was utilized to detect HBsAg in the peripheral blood of pregnant women and the femoral vein blood of their aborted fetuses. HBV-DNA in serum and peripheral blood mononuclear cells (PBMC) and GSTM1 alleles of pregnant women and their aborted fetuses were detected by nested polymerase chain reaction (PCR) and seminested PCR, respectively. We also examined the location of placenta HBsAg and HBcAb using immunohistochemical staining. The expression of placenta HBV-DNA was detected by in situ hybridization.

Results

For the 30 aborted fetuses, the HBV intrauterine infection rate was 43.33 %. The HBV-positive rates of HBsAg in peripheral blood, serum, and PBMC were 10 % (3/30), 23.33 % (7/30), and 33.33 % (10/30), respectively. Maternal–fetal PBMC transport was significantly positively correlated with fetal PBMC HBV-DNA (P = 0.004). Meanwhile, the rates of HBV infection gradually decreased from the maternal side to the fetus side of placenta (decidual cells > trophoblastic cells > villous mesenchymal cells > villous capillary endothelial cells). However, no significant correlation between placenta HBV infection and HBV intrauterine infection was observed (P = 0.410).

Conclusions

HBV intrauterine infection was primarily due to peripheral blood mononuclear cell maternal–fetal transportation in the second trimester in pregnant women.