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首页> 外文期刊>British Journal of Obstetrics and Gynaecology >The scientific basis of antenatal prophylaxis.
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The scientific basis of antenatal prophylaxis.

机译：产前预防的科学依据。

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摘要

BACKGROUND: Standard post-delivery administration of anti-D, together with further anti-D for events known to result in fetomaternal haemorrhage (FMH) during pregnancy, has reduced the incidence of alloimmunisation in RhD women to 0.83-1.5% in the UK. Residual alloimmunisation occurs mainly for two reasons: i) failure to administer sufficient anti-D at the correct time after known at-risk events, either during pregnancy or at delivery; and ii) alloimmunisation during pregnancy as a result of 'silent' FMH. The RhD antigen is well developed by 6 weeks' gestation and the fetoplacental blood volume increases during pregnancy. Studies show that 3% of pregnant women have FMH in the first trimester, 12% in the second, and 45% in the third. Analysis of alloimmunisation in primigravidae clearly shows that on average, 90% are detectable after 28 weeks' gestation. Additional anti-D prophylaxis during the course of pregnancy, starting at 28 weeks, can reduce alloimmunisation to a minimum by protecting against occult FMH. The identification of intrapartum alloimmunisation as being the 'true' cause of alloimmunisation is best assessed by studying first pregnancies, and rigorous analysis of antenatal anti-D efficacy should preferably include observation in second pregnancies to avoid underestimation of alloimmunisation. Ideally there should be no exclusions, i.e. treating both arms of the study on an 'intention to treat' basis, otherwise there will be an overestimate of efficacy under routine practice conditions. Initial safety concerns about effects of antenatal anti-D on the fetus have not been confirmed in practice. OPTIONS: Although there is only one randomised controlled clinical trial (with small numbers) demonstrating a further reduction in alloimmunisation following antenatal administration of anti-D meriting a grade A recommendation (see appendix II), the total body of evidence of efficiency is compelling. Whilst two doses of 300 microg are effective, this is no more so than the single dose in practice, and as it requires considerably more anti-D immunoglobulin, it is probably not cost effective. If a single dose is to be given, it is too late at 34 weeks, and 28 weeks is to be recommended. If divided doses are to be given at 28 and 34 weeks, 50 microg is insufficient, and 100 microg is recommended. Two dose regimes can be recommended, as follows: i) single dose of 300 microg at 28 weeks--the results of the single 300 microg dose in first pregnancies is limited to the Canadian study with observed reduction from 1.6% (45/2768) in concurrent nonrandomised controls to 0.18% (2/1086) in the treatment group. ii) two doses of 100 microg at 28 and 34 weeks--the two controlled studies give similar results in first pregnancies. A reduction in alloimmunisation is seen from 1.11% (4/360) in controls to <0.28% (0/362) in the treatment group in the French study , and from 0.95% (19/2000) in controls to 0.32% (4/1238) in the treatment group in the English study. Whilst anti-D is in limited supply, it is more cost effective to restrict antenatal prophylaxis to first pregnancies. It is also probable that a single dose of 250 microg (as used in Europe) will be as effective in practice as the 300 microg dose, given the limitations of the anti-D quantification assay, and the vial overfill introduced by manufacturers, but this has not been formally proven in clinical trials. The number of RhD deaths is now very low, even with standard postpartum prophylaxis, but there is a systematic underreporting in the UK, due to early fetal deaths being recorded as 'abortion' rather than as haemolytic disease of the newborn (HDN). There have been no systematic studies on the reduction in mortality observed with antepartum anti-D. Nevertheless, it is self-evident that if immunisation is largely prevented, then so will fetal morbidity and mortality.
机译：背景：标准的抗D分娩后给药，以及已知在怀孕期间导致胎儿母系出血（FMH）的事件的进一步抗D，已将英国的RhD妇女的同种免疫发生率降低到0.83-1.5％。残留同种免疫的发生主要有两个原因：i）在已知的高风险事件后（怀孕期间或分娩时）未能在正确的时间给予足够的抗D抗体; ii）由于“无声” FMH而在怀孕期间进行了同种免疫。妊娠6周后RhD抗原发育良好，妊娠期间胎盘胎血量增加。研究表明，妊娠前三个月有3％的孕妇患有FMH，孕中期有12％，孕晚期有45％。对初生狼毒的同种免疫的分析清楚地表明，妊娠28周后平均可检测到90％。从28周开始，在怀孕过程中额外的抗D预防措施可通过防止隐匿性FMH将同种免疫减少到最低程度。产前同种免疫的确定是同种免疫的“真正”原因，最好通过研究第一次怀孕来评估，对产前抗D功效的严格分析最好包括在第二次怀孕中进行观察，以免低估同种免疫。理想情况下不应有任何排除，即在“意图治疗”的基础上治疗研究的两个方面，否则在常规实践条件下会高估疗效。在实践中尚未确认有关产前抗D对胎儿的影响的最初安全问题。方案：尽管只有一项随机对照临床试验（少量）表明产前给予抗D抗体后，同种免疫水平进一步降低，推荐A级推荐（见附录II），但有力的整体证据令人信服。虽然两剂300微克是有效的，但实际上并不比单剂有效，而且由于它需要更多的抗D免疫球蛋白，因此可能并不划算。如果要服用单剂，则在34周时为时已晚，建议28周。如果要在28和34周时分次服用，则50微克是不够的，建议100微克。可以推荐两种剂量方案，如下所示：i）28周单剂300微克-首次妊娠中单剂300微克的结果仅限于加拿大研究，观察到从1.6％降低（45/2768）在并发非随机对照中，治疗组的不良反应率为0.18％（2/1086）。 ii）在28周和34周时分两剂服用100微克-两项对照研究在初次妊娠中得出相似的结果。在法国研究中，治疗组的同种免疫从对照组的1.11％（4/360）降低到<0.28％（0/362），从对照组的0.95％（19/2000）降低到0.32％（4 / 1238）在英语学习中的治疗组中。尽管抗D药物的供应有限，但将产前预防仅限于初次妊娠更具成本效益。考虑到抗D定量测定法的局限性以及制造商引入的小瓶过量，在实践中，单剂量250微克（在欧洲使用）也可能与300微克剂量一样有效。尚未在临床试验中得到正式证明。即使采用标准的产后预防措施，RhD的死亡人数现在也很低，但是在英国，由于早期胎儿死亡被记录为“流产”而不是新生儿的溶血性疾病（HDN），因此在英国有系统的报告不足。尚无关于产前抗D观察到的死亡率降低的系统研究。然而，不言而喻的是，如果很大程度上防止了免疫，那么胎儿的发病率和死亡率也将得到防止。

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