OBJECTIVE: To evaluate the effect of red blood cell (RBC) antibody screening in the 27th week of pregnancy in Rhc-negative @entity1 , on detection of alloimmunisation, undetected at first trimester screening ('late' alloimmunisation), and subsequent @entity6570 ( @entity6570 ), to assess risk factors for late alloimmunisation. DESIGN: Prospective cohort and nested case-control study. SETTING: The Netherlands. POPULATION: Two-year nationwide cohort. METHODS: Prospective inclusion of Rhc-negative @entity1 with negative first trimester screening and of screen-negative controls. Assessment of incidence and numbers needed to screen (NNS) of late alloimmunisation and @entity6570 ; logistic regression analysis to establish risk factors for late alloimmunisation. MAIN OUTCOME MEASURES: Late alloimmunisation, @entity6570 . RESULTS: Late alloimmunisation occurred in 99 of 62 096 (0.159%) Rhc-negative @entity1 ; 90% had c/E antibodies and 10% non-Rhesus antibodies. Severe @entity6570 (fetal/neonatal transfusion) occurred in two of 62 096 (0.003%) of Rhc-negative @entity1 and 2% of late alloimmunisations; moderate @entity6570 (phototherapy) occurred in 20 @entity1 [22.5%; 95% confidence interval (CI), 13.8-31.1%]. Perinatal survival was 100%. The NNS to detect one @entity6570 case was 2823 (31 048 for severe, 3105 for moderate @entity6570 ). Significant risk factors were former blood transfusion [odds ratio (OR), 10.4; 95% CI, 1.14-94.9], parity ( @entity3881 : OR, 11.8; 95% CI, 3.00-46.5; P > 1: OR, 7.77; 95% CI, 1.70-35.4) and amniocentesis/chorionic villus sampling during current pregnancy (OR, 9.20; 95% CI, 1.16-72.9). CONCLUSIONS: Additional screening of Rhc-negative @entity1 improved the detection of late alloimmunisation and @entity6570 , facilitating timely treatment, with a NNS of 2823. Independent risk factors for late alloimmunisation were blood transfusion, parity and chorionic villus sampling/amniocentesis in the current pregnancy. The occurrence of most factors before the current pregnancy suggests a secondary immune response explaining most late alloimmunisations. TWEETABLE ABSTRACT: Third trimester screening for alloimmunisation in Rhc-neg @entity1 improves detection and treatment of severe @entity6570 .

Third trimester screening for alloimmunisation in Rhc-negative pregnant XXXX : evaluation of the Dutch national screening programme.

@entity1 :: ('9606', 'Species') :: ['women', 'children'] @entity3881 :: ('1423', 'Gene') :: ['P-1'] @entity6570 :: ('MESH:D004899', 'Disease') :: ['haemolytic disease of the fetus and newborn', 'HDFN']
@entity1 :: (9606,Species) :: ['women']
