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The neonatal Fc receptor (FcRn) plays an important role in the transfer of the immunoglobulin G isotype (IgG) from the mother to the fetus. FcRn expressed on endothelial cells also binds to IgG and albumin, regulating the circulating half-lives of these proteins. Alloimmune and autoimmune IgG antibodies have been implicated in various perinatal immune-mediated diseases. FcRn-mediated placental transfer of pathogenic antibodies can result in cell and tissue injury in the fetus and neonate, with devastating outcomes. Thus, blockade of FcRn may be an effective treatment strategy in managing these conditions and could additionally reduce the concentration of pathogenic antibodies in the maternal circulation by preventing IgG recycling. In this review, we discuss the biology of FcRn, the rationale and considerations for development of FcRn-blocking agents, and their potential clinical applications in various perinatal immune-mediated diseases. © 2022 International Society of Ultrasound in Obstetrics and Gynecology. [ABSTRACT FROM AUTHOR]

Objective: The perinatal outcomes in second-trimester abdominal circumference (AC) discordant twins are yet to be established. The aim of this study was to ascertain perinatal risks associated with second-trimester AC discordance in monochorionic (MC) twins. Method: We conducted a retrospective study of all MC twin pregnancies over a 7-year period. Intertwin AC discordance at 14–26 gestational weeks was analyzed in relation to Doppler abnormalities, obstetric complications, and perinatal adverse outcomes. Results: A total of 246 MC twin pregnancies were included in the analysis. The smaller twins of second-trimester AC discordant pairs were at increased prevalence of abnormal umbilical artery flow (50% versus 24%, p < .001) and low positive A wave of ductus venous flow (24% versus 9%, p = .002). The second-trimester AC discordant twins were at increased risk of oligohydramnios in smaller twin (OR = 2.44, 95% CI = 1.37–4.32, p < .01), cardiomegaly in larger twin (OR = 2.95, 95% CI = 1.01–8.60, p < .05), birth weight of either twin below the 10th percentile for gestational age (OR = 5.56, 95% CI = 2.67–11.59, p < .001), birth weight discordance > 25% (OR = 9.41, 95% CI = 4.46–19.87, p < .001), IUFD (OR = 3.26, 95% CI = 1.76–6.05, p < .001), and severe neonatal morbidity (OR = 1.83, 95% CI = 1.03–3.26, p < .05). The intact survival rate in discordant and concordant twin pairs was 70% and 89%, respectively (p < .001). Conclusions: Early and increase fetal surveillance of the second-trimester AC discordant twins should be utilized to establish perinatal risks, thus allowing prenatal care to improve. [ABSTRACT FROM AUTHOR]

Objective: The perinatal outcomes in second-trimester abdominal circumference (AC) discordant twins are yet to be established. The aim of this study was to ascertain perinatal risks associated with second-trimester AC discordance in monochorionic (MC) twins.Method: We conducted a retrospective study of all MC twin pregnancies over a 7-year period. Intertwin AC discordance at 14-26 gestational weeks was analyzed in relation to Doppler abnormalities, obstetric complications, and perinatal adverse outcomes.Results: A total of 246 MC twin pregnancies were included in the analysis. The smaller twins of second-trimester AC discordant pairs were at increased prevalence of abnormal umbilical artery flow (50% versus 24%, p < .001) and low positive A wave of ductus venous flow (24% versus 9%, p = .002). The second-trimester AC discordant twins were at increased risk of oligohydramnios in smaller twin (OR = 2.44, 95% CI = 1.37-4.32, p < .01), cardiomegaly in larger twin (OR = 2.95, 95% CI = 1.01-8.60, p < .05), birth weight of either twin below the 10th percentile for gestational age (OR = 5.56, 95% CI = 2.67-11.59, p < .001), birth weight discordance > 25% (OR = 9.41, 95% CI = 4.46-19.87, p < .001), IUFD (OR = 3.26, 95% CI = 1.76-6.05, p < .001), and severe neonatal morbidity (OR = 1.83, 95% CI = 1.03-3.26, p < .05). The intact survival rate in discordant and concordant twin pairs was 70% and 89%, respectively (p < .001).Conclusions: Early and increase fetal surveillance of the second-trimester AC discordant twins should be utilized to establish perinatal risks, thus allowing prenatal care to improve. [ABSTRACT FROM AUTHOR]

Objective: To evaluate which risk factors for RhD immunisation remain, despite adequate routine antenatal and postnatal RhIg prophylaxis (1000 IU RhIg) and additional administration of RhIg. The second objective was assessment of the current prevalence of RhD immunisations. Design Prospective cohort study. Setting: The Netherlands. Population: Two‐year nationwide cohort of alloimmunised RhD‐negative women. Methods: RhD‐negative women in their first RhD immunised pregnancy were included for risk factor analysis. We compared risk factors for RhD immunisation, occurring either in the previous non‐immunised pregnancy or in the index pregnancy, with national population data derived from the Dutch perinatal registration (Perined). Results: In the 2‐year cohort, data from 193 women were eligible for analysis. Significant risk factors in women previously experiencing a pregnancy of an RhD‐positive child (n = 113) were: caesarean section (CS) (OR 1.7, 95% CI 1.1–2.6), perinatal death (OR 3.5, 95% CI 1.1–10.9), gestational age >42 weeks (OR 6.1, 95% CI 2.2–16.6), postnatal bleeding (>1000 ml) (OR 2.0, 95% CI 1.1–3.6), manual removal of the placenta (MRP) (OR 4.3, 95% CI 2.0–9.3); these factors often occurred in combination. The miscarriage rate was significantly higher than in the Dutch population (35% versus 12.‐5%, P < 0.001). Conclusion: Complicated deliveries, including cases of major bleeding and surgical interventions (CS, MRP), must be recognised as a risk factor, requiring estimation of fetomaternal haemorrhage volume and adjustment of RhIg dosing. The higher miscarriage rate suggests that existing RhIg protocols need adjustment or better compliance. Complicated delivery (caesarean section, manual removal placenta, major bleeding) is the most valid risk factor for RhD immunization despite antenatal and postnatal RhIg. Complicated delivery (caesarean section, manual removal placenta, major bleeding) is the most valid risk factor for RhD immunization despite antenatal and postnatal RhIg. [ABSTRACT FROM AUTHOR]

We conclude that currently available data do not indicate a major benefit of IUT for survival or brain injury risk in the anemic cotwin after SFD. Intrauterine transfusion (IUT) can correct successfully fetal anemia in the surviving cotwin after SFD; however, it is unclear if this treatment is beneficial for the long-term prognosis. Single fetal demise (SFD) in monochorionic (MC) twin pregnancy is associated with high risk of perinatal morbidity and mortality of the cotwin, including injury to the brain and other organs due to acute retrograde exsanguination1. [Extracted from the article]