An increased risk for non allo-immunization related intrauterine fetal death in RhD-negative patients

Objective. To investigate immediate perinatal outcome of RhD-negative patients carrying RhD-positive fetuses who received antenatal Rh immunoglobulin for the prevention of RhD-mediated hemolytic disease of the fetus and newborn.

Methods. A retrospective population-based analysis was conducted comparing pregnancies of all RhD-negative women who received antenatal Rh immunoglobulin prophylaxis (anti-D), to RhD-positive parturients, during the years 1988–2003. All women were RhD-negative without evidence of RhD sensitization. Patients received anti-D during the 28–30th week of pregnancy, and an additional dosage within 72 hours following delivery after confirmation of the newborn's RhD status.

Results. Of 145,437 deliveries during the study period, 6.8% were of RhD-negative women (n = 9961). Perinatal mortality rate was significantly higher among the RhD-negative women who received antenatal prophylaxis rhesus immunoglobulin as compared with the controls (17/1000 vs. 12/1000, OR = 1.3, 95%CI 1.2–1.6; p < 0.001). This higher mortality rate was related to a higher rate of intrauterine fetal demise (IUFD) (10/1000 vs. 6/1000, OR = 1.5, 95%CI 1.2–1.9; p < 0.001). The association remained significant after controlling for RhD isoimmunization leading to hydrops fetalis, using the Mantel-Haenszel technique (weighted OR = 1.3; 95% CI 1.1–1.5; p = 0.001). The rate of RhD isoimmunization was 0.6% (n = 58). Using a multivariable analysis with IUFD as the outcome variable, controlling for known confounders for fetal demise, RhD-negative status was an independent risk factor for IUFD.

Conclusion. RhD-negative women carrying RhD-positive newborns are at an increased risk for IUFD despite Rh immunoprophylaxis.     

Repeated severe neonatal hemolysis due to Rhesus isoimmunization in a pregnant woman.

Rhesus (Rh) isoimmunization presenting as severe neonatal hemolytic disease is rare in RhD negative primigravidas of Chinese ethnicity. We report the case of a 32-year-old pregnant Taiwanese woman, RhD negative, who gave birth vaginally to two RhD-positive full-term fetuses 6 years apart. Antenatal follow-up was uneventful and there was no obvious fetal-maternal hemorrhage except at the performance of amniocentesis at the 19th week of the first pregnancy without anti-D immune globulin prophylaxis. Although anti-D immune globulins were administered to the mother within 1 hour after each birth, both of the newborns had severe neonatal hemolysis refractory to phototherapy and were rescued by exchange transfusions. Both of the children were well at age 7-years-old and one-year-old respectively In conclusion, with suspicion of fetal-maternal hemorrhage in RhD-negative pregnancies post amniocentesis, serial monitoring of indirect Coombs titer with appropriate management is mandatory.     

Detection of fetal Rhesus D gene in whole blood of women booking for routine antenatal care

OBJECTIVE: To determine if the RhD status of the fetus can be detected in an unselected group of RhD-negative women with ongoing pregnancies booking for routine antenatal care. MATERIAL AND METHODS: We obtained 2.5 ml of whole blood from 202 unselected women with a normal ongoing pregnancy who booked for antenatal care before 20 weeks' gestation. DNA was extracted and real time quantitative PCR performed. Primers and a specific probe were targeted at the Rhesus D gene. RESULTS: Of 194 women, 31 were RhD-negative with no evidence of prior isoimmunisation. They delivered 17 RhD-positive and 14 RhD-negative babies. Of the 17 RhD-negative women carrying a RhD-positive fetus, the RhD gene was detected in the maternal blood in 14 (82%). There were no false positives. The quantity of RhD gene detected in the maternal blood of RhD-negative mothers ranged from 2 x 10(2) to 4 x 10(6) copies/ml of whole blood. CONCLUSION: Using real time quantitative PCR assays to amplify free fetal DNA in the maternal circulation, identification of RhD-positive fetuses in RhD-negative mothers is feasible when they book for antenatal care. Before such RhD genotyping can be introduced into clinical practice, however, further studies are required to show that false negative results can be eliminated and to show that this diagnostic test is reliable outside a research setting.     

Risk factors for RhD immunisation despite antenatal and postnatal anti-D prophylaxis

Objective  To identify risk factors for Rhesus D (RhD) immunisation in pregnancy, despite adequate antenatal and postnatal anti-D prophylaxis in the previous pregnancy. To generate evidence for improved primary prevention by extra administration of anti-D Ig in the presence of a risk factor.
Design  Case–control study.
Setting  Nation-wide evaluation of the Dutch antenatal anti-D-prophylaxis programme.
Population  Cases: 42 RhD-immunised parae-1, recognised by first-trimester routine red cell antibody screening in their current pregnancy, who received antenatal and postnatal anti-D Ig prophylaxis (gifts of 1000 iu) in their first pregnancy. Controls: 339 parae-1 without red cell antibodies.
Methods  Data were collected via obstetric care workers and/or personal interviews with women.
Main outcome measure  Significant risk factors for RhD immunisation in multivariate analysis.
Results  Independent risk factors were non-spontaneous delivery (assisted vaginal delivery or caesarean section) (OR 2.23; 95% CI:1.04–4.74), postmaturity (≥42 weeks of completed gestation: OR 3.07; 95% CI:1.02–9.02), pregnancy-related red blood cell transfusion (OR 3.51; 95% CI:0.97–12.7 and age (OR 0.89/year; 95% CI:0.80–0.98). In 43% of cases, none of the categorical risk factors was present.
Conclusions  In at least half of the failures of anti-D Ig prophylaxis, a condition related to increased fetomaternal haemorrhage (FMH) and/or insufficient anti-D Ig levels was observed. Hence, RhD immunisation may be further reduced by strict compliance to guidelines concerning determination of FMH and accordingly adjusted anti-D Ig prophylaxis, or by routine administration of extra anti-D Ig after a non-spontaneous delivery and/or a complicated or prolonged third stage of labour.     

Anti-D in Rh(D)-Negative Pregnant Women: Are At-Risk Pregnancies and Deliveries Receiving Appropriate Prophylaxis?

ObjectiveAlthough anti-D prophylaxis has greatly reduced the rate of Rh-immunization, there remain women who sensitize during or after pregnancy because of inadequate prophylaxis. The purpose of this study was to compare adherence to prophylaxis recommendations for antenatal and postnatal anti-D immunoglobulin administration.MethodsWe conducted a retrospective cohort study of all pregnancies recorded at the Royal Victoria Hospital between 2001 and 2006 to determine the rates of antenatal and postnatal prophylaxis in Rh(D)-negative women. We compared adherence to anti-D prophylaxis recommendations between our institution’s physician-dependent antenatal approach and the protocolbased postpartum approach. Logistic regression analysis was used to estimate the odds ratio and 95% confidence intervals of determinants of non-adherence to current recommendations for anti-D prophylaxis.ResultsAntenatal administration was analyzed in 1868 pregnancies in eligible Rh-negative women. Among these women, 85.7% received appropriate antenatal prophylaxis and 98.5% of eligible women received appropriate postnatal prophylaxis. Factors independently associated with non-adherence to antepartum prophylaxis included first visit in the third trimester (P < 0.001), transfer from an outside hospital (P = 0.03), and physician licensing before 1980 (P = 0.04).ConclusionUnlike hospital-based protocol-dependent systems, physician-dependent systems for antenatal anti-D prophylaxis remain subject to errors of omission. A more standardized system is needed to ensure effective antenatal prophylaxis.     

Efficacy and safety of a new, chromatographically purified rhesus (D) immunoglobulin

OBJECTIVES: To study the efficacy, safety, and tolerability of the 300 microg dose of a new chromatographically produced rhesus immunoglobulin (Rhophylac 300) for ante- and postnatal rhesus prophylaxis. DESIGN: In an open-label multi-centre study, rhesus D (RhD)-negative women were randomly allocated to receive Rhophylac 300 either intravenously or intramuscularly at the 28th week of gestation and within 72 h after delivery of an RhD-positive child. Serum samples were obtained prior to the antenatal dose and 6-11.5 months after delivery of an RhD-positive child and tested by the indirect antiglobulin test and papain test for anti-D. Safety parameters were assessed in all women who were treated with the study drug. RESULTS: Four hundred and thirty two women received the study drug antenatally. No differences were detected in efficacy or tolerability between intravenous and intramuscular administration. Of the 261 women who delivered an RhD-positive child and received rhesus prophylaxis according to the protocol, 248 women returned for follow-up investigations. None of them had detectable anti-D at their last visit. There were no serious adverse events, no cases of infectious disease transmission nor clinically relevant changes in laboratory safety values and vital signs attributable to the study drug. CONCLUSIONS: The results suggest that Rhophylac 300 given intravenously or intramuscularly is safe and efficacious in preventing rhesus (D) immunisation.     

Non-invasive fetal RHD exon 7 and exon 10 genotyping using real-time PCR testing of fetal DNA in maternal plasma

OBJECTIVE: In this prospective study, we assessed the feasibility of foetal RHD genotyping by analysis of DNA extracted from plasma samples of Rhesus (Rh) D-negative pregnant women using real-time PCR and primers and probes targeted toward exon 7 and 10 of RHD gene. METHODS: We analysed 24 RhD-negative pregnant woman and 4 patients with weak D phenotypes at a gestational age ranging from 11th to 38th week of gestation and correlated the results with serological analysis of cord blood after the delivery. RESULTS: Non-invasive prenatal foetal RHD exon 7 genotyping analyses of maternal plasma samples was in complete concordance with the serological analysis of cord blood in all 24 RhD-negative pregnant women delivering 12 RhD-positive and 12 RhD-negative newborns. RHD exon-10-specific PCR amplicons were not detected in 2 out of 12 studied plasma samples from women bearing RhD-positive foetus, despite the positive amplification in RHD exon 7 region observed in all cases. In 1 case red cell serology of cord blood revealed that the mother had D-C-E-c+e+ C(w)- and the infant D+C-E-c+e+ C(w)+ phenotypes. RhD exon 10 real-time PCR analysis of cord blood was also negative. These findings may reflect that DC(w)- paternally inherited haplotype probably possesses no RHD exon 10. In another case no cord blood sample has been available for additional studies. The specificity of both RHD exon 7 and 10 systems approached 100% since no RhD-positive signals were detected in women currently pregnant with RhD-negative foetus (n = 8). Using real-time PCR and DNA isolated from maternal plasma, we easily differentiated pregnant woman whose RBCs had a weak D phenotype (n = 4) from truly RhD-negative patients since the threshold cycle (C(T)) for RHD exon 10 or 7 amplicons reached nearly the same value like C(T) for control beta-globin gene amplicons detecting the total DNA present in maternal plasma. However in these cases foetal RhD status cannot be determined. CONCLUSION: Prediction offoetal RhD status from maternal plasma is highly accurate and enables implementation into clinical routine. We suggest that safe non-invasive prenatal foetal RHD genotyping using maternal plasma should involve the amplification of at least two RHD-specific products.     

Stillbirth at term in women of advanced maternal age in the United States: when could the antenatal testing be initiated?

We sought to determine if advanced maternal age (AMA) is a risk factor for intrauterine fetal demise (IUFD). We used a U.S. Centers for Disease Control and Prevention database and analyzed outcomes in women 15 to 44 years of age with term singleton gestations. Cox proportional hazards models and Cochran-Mantel-Haenszel tests were used. Results were controlled for maternal race and smoking. After excluding congenital anomalies and medical complications, 6,239,399 singleton term deliveries were identified. When compared with women 25 to 29 years of age, the risk of IUFD increased with advancing age: 30 to 34 years, odds ratio [OR] = 1.24 (95% confidence interval [CI], 1.13 to 1.36); 35 to 39 years, OR = 1.45 (95% CI, 1.21 to 1.74), and 40 to 44 years, OR = 3.04 (95% CI, 1.58 to 5.86). The risk of IUFD for women 40 to 44 years of age at 39 weeks is comparable with that of 42 weeks in those 25 to 29 years of age. We concluded that AMA is an independent predictor of IUFD, and a strategy of antenatal testing in those > or = 40 years of age beginning at 38 weeks may be considered.     

The kinetics of routine antenatal prophylactic intramuscular injections of polyclonal anti-D immunoglobulin

OBJECTIVE: To observe the pharmacokinetics of intramuscular anti-D immunoglobulin (IgG) given for routine antenatal prophylaxis. DESIGN: Prospective observational study. SETTING: Maternity unit and antenatal serology laboratory in a district teaching hospital. POPULATION: Forty-five rhesus-D-negative pregnant women not sensitised to RhD. METHODS: Serial serum quantitations of anti-D IgG following the intramuscular injections of anti-D IgG 100 microg (500 IU) at 28 and 34 weeks of gestation. Anti-D IgG concentrations were assayed with the RFA-300 continuous flow analyser. MAIN OUTCOME MEASURES: The kinetic profile and duration of detectable anti-D IgG in maternal serum following the first and second injections of anti-D IgG. RESULTS: For the 43 women in whom serial data were collected, there were no detectable differences between pregnancies with an RhD-positive (26) or -negative (17) fetus. Maximum IgG concentrations were detected two to five days following the first anti-D IgG injection and ranged between 0 and 28 ng/mL. Only 30% of women still undelivered at 40 weeks of gestation had detectable IgG at 2 ng/mL or greater. There was a significant relationship between higher maximum values and low maternal surface body area (R2 = 0.204, P = 0.002), but this did not influence duration of persistent IgG. CONCLUSION: Using previously published data, 70% women are not adequately protected with anti-D IgG 12 weeks after the first prophylactic injection. Despite this, previous clinical results suggest that the antenatal prophylaxis schedule used provides adequate protection and that the recommendation for the lowest concentration of protective anti-D IgG antibody levels currently in use is probably overestimated.     

Prenatal determination of the fetal RhD blood group by multiplex PCR: a 7-year Portuguese experience

OBJECTIVES: This is a retrospective study to evaluate the efficacy and accuracy of the multiplex polymerase chain reaction (PCR) amplification, for early detection of fetuses at risk for hemolytic disease, in the population living in Portugal, and to characterize the RhD-negative individuals at serologic and molecular level. METHODS: 2030 uncultured amniotic fluid samples and 2012 blood samples from the respective RhD-negative pregnant women were studied by multiplex PCR of intron 3/intron 4, exon 7 and 3'UTR. Amniocentesis was performed for a variety of medical indications. For quality control, serologic RhD blood groups were determined in the cord blood, after birth. RESULTS: 1361 fetal amniotic samples were RhD-positive (67%), 669 were RhD-negative. The average time for diagnosis was 2 days for uncultured amniocytes and the molecular versus serologic RhD typing (n = 809) had 99.5% concordance. Among the 2012 serologic RhD-negative mothers, 26 had an RhD-positive allele. CONCLUSION: The multiplex PCR amplification used in this study was a rapid and accurate method to determine the RhD blood type in the population living in Portugal, being a great tool for management of pregnancies with fetuses at risk for alloimmune hemolytic disease. In this population, 1.3% of the serologic RhD-negative women have an RHD-positive allele.     

An audit of anti-D sensitisation in Yorkshire

Objective To determine the likely factors that contribute to RhD sensitisation.
Design Retrospective study of all new cases of RhD sensitisation occurring between 1988 and 1991.
Setting Leeds Blood Centre, National Blood Service, Yorkshire.
Population One hundred and forty-seven cases of RhD sensitisation from 15 obstetric units within the Yorkshire region, of which 129 (312 pregnancies) could be assessed.
Main outcome measures Identification of potential immunising events and adherence with recommendations on anti-D immunoglobulin administration.
Results Twenty-eight women (22%) had immune anti-D antibodies during their first pregnancy or at delivery and 50 (39%) in their second pregnancy. Overall, 98 potential immunising events were identified in 62 women, excluding delivery; 67 women (52%) had no events, other than delivery. Miscarriages and medical terminations of pregnancy accounted for 81% of all identified events. Iatrogenic failure to adhere to recommendations for the administration of anti-D immunoglobulin occurred in a significant proportion of women who subsequently developed immune anti-D antibodies. Anti-D immunoglobulin failed to protect against immunisation despite adherence to the protocol in 20 events (20%), 13 of which involved miscarriages or termination of pregnancy < 20 weeks of gestation. Potentially, antenatal prophylaxis might have prevented 86% of immunisations that were identified during the first pregnancy.
Conclusions The introduction of antenatal administration of anti-D immunoglobulin could significantly reduce the level of sensitisation in primigravidae, and adherence to recommendations for administration of anti-D immunoglobulin could be improved. Consideration should be given to reviewing the current recommendation that a dose of 250 IU of anti-D immunoglobulin is adequate following termination of pregnancy before a gestational age of 20 weeks.     

Antecedents to and Outcomes of Rh(D) Isoimmunization: Mater Mothers Hospital, Brisbane, 1988–1995

Summary: We analyzed the antecedents and outcomes of Rh(D) isoimmunization in a local population. Forty-two Rh(D) isoimmunized women attending Mater Mothers Hospital for antenatal care were identified through the Mater Hospital Blood Bank database; their records were reviewed for variables including sensitizing events, obstetric interventions and pregnancy outcomes. In this group, 74% of women became sensitized despite receiving anti-D immune globulin, 17% did not receive anti-D appropriately and the others failed to attend for treatment of bleeding in pregnancy. Antenatal sensitization was implicated in 6 women (14%) and potentially responsible for isoimmunization in another 18. Over half of the 80 viable pregnancies in this study group required some form of obstetric intervention. Thirty pregnancies required amniocentesis and 1 in 3 babies underwent either intrauterine or exchange transfusion. Three fetal deaths occurred as a result of severe disease. This study offers information highlighting circumstances in which immunoprophylaxis guidelines have failed to impart protection against Rh(D) sensitization and the consequences of such failures.     

Noninvasive determination of fetal RhD status using fetal DNA in maternal serum and PCR

OBJECTIVE: Because prenatal testing of fetal RhD status by amniocentesis carries small yet finite risks to the fetus and mother, this study sought to determine whether fetal DNA in maternal serum could be used to detect fetal RhD status by polymerase chain reaction (PCR). METHODS: A retrospective analysis was made of frozen serum specimens from 20 sensitized RhD-negative pregnant women (ranging from 15.0 to 36.0 weeks' gestation) who were confirmed by serology at birth to have been carrying RhD-positive fetuses. Eleven serum specimens from RhD-negative individuals served as controls. DNA was isolated from serum and used in two PCR-based methods to detect a 99 base pair (bp) DNA fragment specific for the RhD gene and a 113 bp fragment specific for the RhCE gene as control. RESULTS: Overall, in 14 (70%) of 20 RhD-positive fetuses the 99 base pair RhD-specific PCR product was detected. There was no false positive detection among the 11 control serum specimens. CONCLUSION: The results illustrate the ability to detect fetal RhD sequences in maternal serum of sensitized women. Moreover, the findings demonstrate that fetal single-gene disorders can be detected prenatally by using DNA isolated only from maternal serum.     

Compliance with routine antenatal rhesus D prophylaxis and the impact on sensitisations: observations over 14 years

Documented routine antenatal anti-D prophylaxis was given to 90% and 81-87% of eligible women at 28 and 34 weeks of gestation, respectively, during the early 1990s and early 2000s. With increasing experience and education, a significant improvement in the timing of the first (OR 0.26, 95% CI 0.16-0.41: P < 0.0001) and second injections (OR 0.40, 95% CI 0.26-0.61: P < 0.0001) occurred during the latter period. Despite these improvements, there was no reduction in the sensitisation rate at 0.4%. However, this low rate occurred despite significant proportions of women delivering more than 42 days after the second injection. Fifteen of the 16 sensitised women had received routine antenatal prophylaxis.     

The economics of routine antenatal anti-D prophylaxis for pregnant women who are rhesus negative

OBJECTIVE: To investigate the economics of routine antenatal anti-D prophylaxis in the prevention of haemolytic disease of the newborn, in support of the NICE appraisals process. DESIGN: Cost effectiveness analysis. SETTING: UK NHS. POPULATION/SAMPLE: Pregnant women who are RhD-negative. METHODS: A model was constructed to estimate the incremental cost effectiveness and cost utility of: (1) offering routine antenatal anti-D prophylaxis to all pregnant women who are RhD-negative; (2) offering routine antenatal anti-D prophylaxis to RhD-negative primigravidae, compared with conventional management alone. Effectiveness estimates were derived from a meta-analysis of two UK community-based studies. Costs were derived from published sources and NHS product lists. Threshold analysis was conducted to reflect the social value of routine antenatal anti-D prophylaxis through incorporating valuations of parental grief and fetal/neonatal loss. MAIN OUTCOME MEASURES: Cost per life year gained and cost per quality adjusted life year (QALY) gained. RESULTS: The cost per life year gained is in the range pound 5,000- pound 15,000. The inclusion of long term neurodevelopmental problems results in a cost utility ranging between pound 11,000 and pound 52,000 per QALY gained. Threshold analysis suggests that if fetal loss, parental grief and subsequent high intervention pregnancy are valued at greater than 9 QALYs, the comprehensive policy would be more attractive than the primigravidae policy, assuming a maximum acceptable threshold of pound 30,000 per QALY. CONCLUSION: Routine antenatal anti-D prophylaxis provides a cost effective intervention for preventing haemolytic disease of the newborn in the pregnancies of women who are RhD-negative.     

Management of isoimmunization in the presence of multiple maternal antibodies

OBJECTIVE: Evaluation and management of patients with multiple maternal antibody isoimmunization is unclear. The presence of > or = 1 maternal antibody may suggest a worse scenario. The objective of this study was 2-fold: first, to determine whether the presence of multiple antibodies predicts a more severe course than single antibodies and second, to determine the utility of the Queenan curves/protocol in evaluating multiple-antibody isoimmunization. STUDY DESIGN: Amniotic fluid DeltaOD(450) measurements were obtained from the antenatal testing logbook and confirmed by chart review. Cases were categorized by antibody type and clinical outcomes obtained by chart review. RESULTS: Twenty-four pregnancies with isoimmunization and multiple maternal antibodies were identified; of these, 17 had 2 antibodies (anti-D and -C in 13; anti-D and -E in 1; anti-D and -Jka in 1; anti-c and -E in 1; and anti-c and -Jka in 1), and 7 had > 2 antibodies (anti-D, -C, and -E in 4; anti-D, -C, and -N in 1; anti-c, -E, and -FYA in 1; and anti-E, -K, -Fya, -S, and -C in 1). Eleven patients (46%) required at least 1 intrauterine fetal transfusion (mean initial fetal hematocrit, 15%; range, 4.9%-24%). In those not transfused, no DeltaOD(450) measurements occurred in the Queenan "fetal death risk" zone. Poorest outcomes (multiple transfusions/hydrops/fetal demise) were in patients with anti-D and anti-C, with or without anti-E. The absence of anti-D was associated with no need for fetal transfusions. The overall transfusion rate was significantly higher compared with a group of 57 isoimmunization patients with only anti-D (46% vs. 25%, P < or =.05). CONCLUSIONS: The presence of anti-D appears to be the most significant factor guiding the course of isoimmunization with multiple antibodies. The presence of another antibody with anti-D appears to significantly increase the need for intrauterine fetal transfusions. The Queenan protocol can successfully treat patients with multiple maternal red blood cell antibodies.     

Pharmacokinetics of anti-D IgG in pregnant RhD-negative women

Objective To assess the pharmacokinetics of anti-D IgG in pregnant Rhesus D-negative women after intramuscular and intravenous administration of 300 μg of Rhophylac.
Design An open, randomised, multicentre study.
Setting Seven gynaecological practices in Germany.
Sample Fourteen RhD-negative pregnant women at risk of becoming Rhesus D immunised received study drug at 28th week of pregnancy either by intramuscular or intravenous route.
Main outcome measures Anti-D IgG concentrations of serum samples obtained up to 11 weeks following antenatal Rhesus D prophylaxis were quantified by flow cytometry.
Results Mean anti-D IgG concentrations after intravenous and intramuscular administration differed up to seven days post-injection, from two weeks onwards they were comparable to each other. Irrespective of the administration route, anti-D IgG in serum was detectable in all women up to at least nine weeks post-administration.
Conclusions The serum concentrations of anti-D IgG measured after administration of Rhophylac were very similar to those obtained with 300 μg of a different anti-D immunoglobulin product.     

Routine antenatal Rhesus D immunoglobulin prophylaxis: the results of a prospective 10 year study.

OBJECTIVE: To assess the clinical and financial impact, and identify the problems, of providing routine antenatal RhD immunoglobulin prophylaxis for Rhesus D negative nulliparae. DESIGN: A retrospective (1980-1986) and prospective (1987-1996) comparison between two similar populations, one population with nulliparae offered routine RhD immunoglobulin 500 IU prophylaxis at 28 and 34 weeks of gestation part way through the study period, and the other population not offered prophylaxis at any time. SETTING: Obstetric units in two counties (three health districts) with similar annual numbers of maternities and the Regional Blood Transfusion Service antenatal serology laboratory. PARTICIPANTS: Non-sensitised Rhesus D negative pregnant nulliparae. INTERVENTIONS: Intramuscular RhD immunoglobulin 500 IU at 28 and 34 weeks of gestation to eligible women booked for confinement in one county; the intervention not offered in the other county. MAIN OUTCOME MEASURES: 1. Rhesus D sensitised second pregnancy rate; 2. success in providing prophylaxis to eligible women; 3. serology laboratory activity changes; 4. potential savings from the prophylaxis programme. RESULTS: Prophylaxis significantly reduced iso-immunisation in the next pregnancy when compared with historical (OR 0.28, CI 0.14-0.53; P < 0.0001) and contemporary controls (OR 0.43, CI 0.22-0.86; P = 0.02). However, success at achieving comprehensive prophylaxis was disappointing, with only 89% of eligible women receiving the first injection, 74% both injections, and for only 29% were both at the correct gestation. Fifty-two percent of women delivered after 40 weeks of gestation, beyond the period of adequate prophylaxis protection. The savings in antenatal interventions, neonatal care and possible long term ill-health that result from very preterm birth should be considerable. CONCLUSION: Routine prophylaxis for nulliparae significantly reduces the incidence of sensitised next pregnancies with consequent savings, and its adoption nationwide should be encouraged. A programme offering antenatal prophylaxis for all Rhesus D negative women is unlikely to be economic. Improvement in uptake of prophylaxis is needed; alternative administration strategies should be explored.