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Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been approved for emergency use, but, despite elevated risk of severe disease, pregnant women were excluded from the clinical trials that led to their authorization.1 Placental findings can indicate potential clinical risk and could be an early signal for rare injury seen only after widespread use in the pregnant population.2–6 Maternal SARS-CoV-2 infection has been associated with decidual arteriopathy, fetal vascular malperfusion, and chronic histiocytic intervillositis.7–9 mRNA vaccines induce an immune response through activation of TLR3, which has been linked to decidual arteriopathy, growth restriction, preterm delivery, and fetal loss in mouse models.10–14 Our objective was to evaluate the frequency of these key placental lesions in patients who received SARS-CoV-2 vaccination in pregnancy.

OBJECTIVE: To examine whether there are characteristic histological features in placentas from ongoing pregnancies of patients with a history of recurrent miscarriage, with and without primary antiphospholipid antibody syndrome, in relation to clinical pregnancy outcome.METHODS: Patients attending a recurrent miscarriage clinic were investigated and treated according to an established protocol. One hundred twenty-one consecutive patients achieving a potentially viable pregnancy (at least 24 completed weeks' gestation), including 60 primary antiphospholipid antibody syndrome-positive cases and 61 primary antiphospholipid antibody syndrome-negative cases were included. After delivery, placental pathologic examination was carried out by a pathologist unaware of the clinical details. Histological sections were examined by two pathologists independently. Pregnancy outcome and placental findings were reviewed in relation to the maternal antiphospholipid antibody status.RESULTS: Pregnancy outcome was similar in primary antiphospholipid antibody syndrome-positive and primary antiphospholipid antibody syndrome-negative groups regarding gestation at delivery and antepartum obstetric complications. Several histological placental abnormalities were identified in both groups, but most pregnancies were clinically uncomplicated, with no significant placental abnormalities. In cases with pregnancy complications, the placental pathology was primarily that of uteroplacental vasculopathy, such as placental infarction and preeclampsia, but there were no specific placental lesions or patterns of abnormalities characteristic of primary antiphospholipid antibody syndrome-positive patients. A small subgroup of primary antiphospholipid antibody syndrome-positive patients may be at increased risk of development of maternal floor infarction or massive perivillus fibrin deposition.CONCLUSION: There are no specific histopathologic placental abnormalities characteristic of treated patients with antiphospholipid antibody syndrome and poor reproductive history, but complications of uteroplacental disease are more common. (C) 2003 by The American College of Obstetricians and Gynecologists.

Objective: To evaluate differences in pregnancy outcomes and placental findings among severely discordant monochorionic and dichorionic twins. Methods: We studied retrospectively a cohort of 382 twin pregnancies with gestational ages that ranged from 24 to 40 weeks. Pregnancies were classified as dichorionic or monochorionic by histologic examination of placentas. Infants were subdivided into concordant (less than 5% difference in birth weight), mildly discordant (5–25% difference), and severely discordant groups (more than 25% difference), and their clinical characteristics and findings at placental examination were analyzed and compared. Results: Severe discordance occurred significantly more often in monochorionic than in dichorionic twins and was associated with significantly more deliveries before 36 weeks and more newborns remaining more than 10 days in the neonatal intensive care unit. Severely discordant monochorionic and dichorionic twins had significantly worse perinatal mortality and morbidity than mildly discordant and concordant twins. The weight of the placenta of the smaller fetus in severely discordant dichorionic twins with separate placentas and the total placental weight in severely discordant monochorionic twins were significantly smaller than the weights of the placentas in their concordant and mildly discordant counterparts. The umbilical cords of the smaller fetuses in both dichorionic and monochorionic pregnancies exhibited significantly more velamentous insertions and single umbilical arteries than in concordant or mildly discordant twins of similar chorionicity. Conclusion: Severe discordance is more frequent and has greater morbidity in monochorionic than dichorionic twins. The most frequent findings in the placentas of severely discordant twins were small placental weight and umbilical cord abnormalities.