Rhesus isoimmunisation in unsensitised RhD-negative individuals seeking abortion at less than 12 weeks' gestation: a systematic review.

AIM: The aim of this review was to systematically review the outcome of routine anti-D administration among unsensitised rhesus (RhD)-negative individuals who have an abortion. This review is registered with Prospero. METHODS: A search for all published and ongoing studies, without restrictions on language or publication status, was performed using the following databases from their inception: EBM Reviews Ovid - Cochrane Central Register of Controlled Trials, MEDLINE Ovid (Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily), Embase.com, Popline and Google Scholar. Study types included: randomised controlled trials, controlled trials, cohort and case-control studies from 1971 onwards. The population included women who undergo an abortion (induced, incomplete, spontaneous or septic abortion), medical or surgical <12 weeks, and isoimmunisation in a subsequent pregnancy. The primary outcomes were: (1) development of a positive Kleihauer-Betke test and (2) development of Rh alloimmunisation in a subsequent pregnancy. RESULTS: A total of 2652 studies were screened with 105 accessed for full-text review. Two studies have been included with high bias appreciated. Both studies found few women to be sensitised in forming antibodies after an abortion. The limited studies available and heterogeneity prevent the conduction of a meta-analysis. CONCLUSIONS: Rh immunoglobulin has well-documented safety. However, it is not without risks and costs, is a possible barrier to delivering efficient services, and may have limited availability in some countries. The evidence base and quality of studies are currently limited. There is unclear benefit from the recommendation for Rh testing and immunoglobulin administration in early pregnancy. More research is needed as clinical practice guidelines are varied, based on expert opinions and moving away from testing and administration at time of abortion. IMPLICATIONS: There is limited evidence surrounding medical benefit of Rh testing and immunoglobulin administration in early pregnancy. Further research is needed to define alloimmunisation and immunoglobulin benefit to update standards of care. Additionally, other factors should be considered in forming clinical policies and guidelines such as costs, feasibility and impact on access to care for patients.