Fowler M G
Efficacy Trials Branch, Division of AIDS, National Institute of Allergy and Infectious Diseases, National Institute of Health, Rockville, MD 20892, USA.
Curr Opin Obstet Gynecol. 1997 Dec;9(6):343-8.
Mother-to-child transmission near the time of birth is the primary route of HIV-1 infection among infants and young children. Throughout the world, 1000 babies a day become infected with HIV, and cumulative global estimates are that 3 million children have been infected since the HIV pandemic began. Although major advances have been made in reducing mother-to-child transmission of HIV-1 in the USA and Europe through the use of an intensive regimen of zidovudine, many research questions remain unresolved. These include (1) viral and host characteristics which hinder or facilitate perinatal HIV transmission (i.e. the role played by viral load, the placenta and obstetric risk factors); (2) the proportion of transmission occurring in utero, intrapartum or during the breast feeding period; and (3) the mode of action of the successful zidovudine regimen. Studies published within the past year have shed light on several of these research topics. In 1996-1997 a number of important studies were published which support a general correlation between maternal viral load and infant HIV infection. The most recent studies do not, however, support the theory that there is a threshold below which transmission cannot occur, and also indicate that zidovudine, given according to the US Public Health Service guidelines, can significantly reduce the risk of transmission across all levels of maternal viral load. Analyses of viral load data from the successful clinical trial with zidovudine (AIDS Clinical Trial Group 076) suggest that its primary action is not by reducing the viral load, and raise the possibility that administering antiretroviral prophylaxis to the infant at the time of highest exposure may be another reason for the reduction in transmission. Obstetric risk factors for mother-to-child HIV transmission have been evaluated in several large cohort studies. A duration of membrane rupture of more than 4 h, and procedures such as amniocentesis, preterm labor, and the presence of sexually transmitted diseases during pregnancy were found to be significant risk factors. Still unresolved is the potential protective effect of cesarean section in reducing the risk of transmission. Likewise, the role played by the placenta in preventing or facilitating perinatal transmission is not well understood, and requires further research. This year did see the publication of consistent findings from diverse geographical regions regarding the probable timing of perinatal HIV transmission. On the basis of the timing of the first infant positive polymerase chain reaction or culture, most transmission would appear to occur around the intrapartum or very late prenatal period, and only approximately 12-14% is related to breast feeding. These advances should help focus and refine future research efforts to reduce mother-to-child HIV transmission worldwide.
出生前后的母婴传播是婴幼儿感染HIV-1的主要途径。在全球范围内，每天有1000名婴儿感染HIV，据全球累计估算，自艾滋病大流行开始以来，已有300万儿童受到感染。尽管美国和欧洲通过使用齐多夫定强化治疗方案，在降低HIV-1母婴传播方面取得了重大进展，但许多研究问题仍未得到解决。这些问题包括：（1）阻碍或促进围产期HIV传播的病毒和宿主特征（即病毒载量、胎盘和产科危险因素所起的作用）；（2）在子宫内、分娩时或母乳喂养期间发生传播的比例；（3）成功的齐多夫定治疗方案的作用方式。过去一年发表的研究对其中一些研究课题有所阐明。1996 - 1997年发表了多项重要研究，支持母体病毒载量与婴儿HIV感染之间的普遍关联。然而，最新研究并不支持存在一个低于此水平就不会发生传播的阈值这一理论，并且还表明，按照美国公共卫生服务指南给予齐多夫定，可显著降低所有母体病毒载量水平下的传播风险。对齐多夫定成功临床试验（艾滋病临床试验组076）的病毒载量数据进行分析表明，其主要作用并非降低病毒载量，并提出在婴儿暴露最高时给予抗逆转录病毒预防措施可能是传播减少的另一个原因。在几项大型队列研究中评估了母婴HIV传播的产科危险因素。发现胎膜破裂持续时间超过4小时以及羊膜穿刺术、早产和孕期性传播疾病等情况是显著的危险因素。剖宫产在降低传播风险方面的潜在保护作用仍未解决。同样，胎盘在预防或促进围产期传播中所起的作用也尚未完全了解，需要进一步研究。今年确实发表了来自不同地理区域关于围产期HIV传播可能时间的一致研究结果。根据首次婴儿聚合酶链反应阳性或培养的时间，大多数传播似乎发生在分娩时或产前很晚的时候，只有约12 - 14%与母乳喂养有关。这些进展应有助于集中和完善未来在全球范围内减少母婴HIV传播的研究工作。
