The effect of influenza virus infection on pregnancy outcomes: A systematic review and meta-analysis of cohort studies

Influenza in Pregnancy: Maternal, Obstetric, and Fetal Implications, Diagnosis, and Management

Influenza(flu) in pregnancy is associated with higher rates of hospitalization, ICU admission, and death and with increased odds of congenital anomalies and stillbirth, but not preterm birth. Clinical manifestations of flu in pregnancy are the same as nonpregnant patients. Pregnant individuals with flu-like symptoms or flu exposure should be treated with antivirals. Diagnostic testing is not needed. Oseltamivir is the mainstay of treatment(and prophylaxis), and when given within 48 hours of symptom onset, it decreases morbidity and mortality. Influenza is associated with worse maternal, obstetric, and neonatal outcomes. These risks are mitigated by early oseltamivir treatment and maternal vaccination; hence the recommendation for universal vaccination in pregnancy.

Burden of Respiratory Syncytial Virus-Associated Acute Respiratory Infections During Pregnancy

BACKGROUND

With the licensure of maternal respiratory syncytial virus (RSV) vaccines in Europe and the United States, data are needed to better characterize the burden of RSV-associated acute respiratory infections (ARI) in pregnancy. The current study aimed to determine among pregnant individuals the proportion of ARI testing positive for RSV and the RSV incidence rate, RSV-associated hospitalizations, deaths, and perinatal outcomes.

METHODS

We conducted a systematic review, following PRISMA 2020 guidelines, using 5 databases (Medline, Embase, Global Health, Web of Science, and Global Index Medicus), and including additional unpublished data. Pregnant individuals with ARI who had respiratory samples tested for RSV were included. We used a random-effects meta-analysis to generate overall proportions and rate estimates across studies.

RESULTS

Eleven studies with pregnant individuals recruited between 2010 and 2022 were identified, most of which recruited pregnant individuals in community, inpatient and outpatient settings. Among 8126 pregnant individuals, the proportion with ARI that tested positive for RSV ranged from 0.9% to 10.7%, with a meta-estimate of 3.4% (95% confidence interval [CI], 1.9%-54%). The pooled incidence rate of RSV among pregnant individuals was 26.0 (95% CI, 15.8-36.2) per 1000 person-years. RSV hospitalization rates reported in 2 studies were 2.4 and 3.0 per 1000 person-years. In 5 studies that ascertained RSV-associated deaths among 4708 pregnant individuals, no deaths were reported. Three studies comparing RSV-positive and RSV-negative pregnant individuals found no difference in the odds of miscarriage, stillbirth, low birth weight, and small size for gestational age. RSV-positive pregnant individuals had higher odds of preterm delivery (odds ratio, 3.6 [95% CI, 1.3-10.3]).

CONCLUSIONS

Data on RSV-associated hospitalization rates are limited, but available estimates are lower than those reported in older adults and young children. As countries debate whether to include RSV vaccines in maternal vaccination programs, which are primarily intended to protect infants, this information could be useful in shaping vaccine policy decisions.

The contributions of parental lactation on offspring development: It's not udder nonsense!

The Developmental Origins of Health and Disease (DOHaD) hypothesis describes how maternal stress exposures experienced during critical periods of perinatal life are linked to altered developmental trajectories in offspring. Perinatal stress also induces changes in lactogenesis, milk volume, maternal care, and the nutritive and non-nutritive components of milk, affecting short and long-term developmental outcomes in offspring. For instance, selective early life stressors shape the contents of milk, including macro/micronutrients, immune components, microbiota, enzymes, hormones, milk-derived extracellular vesicles, and milk microRNAs. In this review, we highlight the contributions of parental lactation to offspring development by examining changes in the composition of breast milk in response to three well-characterized maternal stressors: nutritive stress, immune stress, and psychological stress. We discuss recent findings in human, animal, and in vitro models, their clinical relevance, study limitations, and potential therapeutic significance to improving human health and infant survival. We also discuss the benefits of enrichment methods and support tools that can be used to improve milk quality and volume as well as related developmental outcomes in offspring. Lastly, we use evidence-based primary literature to convey that even though select maternal stressors may modulate lactation biology (by influencing milk composition) depending on the severity and length of exposure, exclusive and/or prolonged milk feeding may attenuate the negative in utero effects of early life stressors and promote healthy developmental trajectories. Overall, scientific evidence supports lactation to be protective against nutritive and immune stressors, but the benefits of lactation in response to psychological stressors need further investigation.

Modern Approaches in Immunoprophylaxis of Infectious Diseases During Pregnancy

Every year more countries recommend vaccination for pregnant women. Nowadays, the spectrum of vaccines that can be used during pregnancy is expanding. Experts of the Union of Pediatricians of Russia have completely updated the section about the pregnant women immunoprophylaxis within updating clinical guidelines on normal pregnancy management. This section is presented in the following article.

Viral pulmonary infection in pregnancy - Including COVID-19, SARS, influenza A, and varicella

The COVID-19 pandemic has been at the forefront of medicine over the last few years. Pregnant women are often exposed to infectious agents that can be harmful not only to the mother but also to the foetus. Moreover, changes during pregnancy means that pregnant women have increased vulnerability to viral infections, especially pulmonary infections. Epidemiological studies have shown a link between maternal viral infections and miscarriage, preterm birth as well as congenital defects. With potential poor outcomes for both women and their newborns, having a good understanding of the presentation and management of these viral pulmonary infections is essential. The increased risk of adverse outcomes has been highlighted during the COVID-19, SARS and H1N1 influenza pandemics.

Knowledge, attitudes, and practices regarding seasonal influenza vaccination during pregnancy in Costa Rica: A mixed-methods study

BACKGROUND

Influenza increases stillbirth risk, morbidity and mortality in pregnant women. Vaccination protects pregnant women against severe disease and indirectly protects their infants, but coverage among pregnant women remains low worldwide. We aimed to describe knowledge, attitudes, and practices (KAP) regarding seasonal influenza vaccination among postpartum women and prenatal care physicians in Costa Rica.

METHODS

We conducted cross-sectional KAP surveys to women one to three days after childbirth at Costa Rican Social Security Fund maternity hospitals, and obstetricians and general practitioners who provided prenatal care in 2017. Principal components analysis, multiple imputation, and logistic regression were used to examine associations between influenza vaccination and demographics, prenatal care, and sources of information-separately for postpartum women and physicians. We also held two focus groups of six healthcare workers each to further describe vaccination KAP.

RESULTS

We surveyed 642 postpartum women and 146 physicians in maternity hospitals in five Costa Rican provinces of whom 85.5 % (95 % CI: 82.6 %-88.0 %) and 57.9 % (95 % CI: 49.6 %-65.7 %) were vaccinated for influenza, respectively. Factors associated with influenza vaccination for postpartum women included tetanus vaccination (aOR: 3.62, 95 % CI: 1.89-6.92); received vaccination recommendations from clinicians during prenatal check-ups (aOR: 3.39, 95 % CI: 2.06-5.59); had other children in household vaccinated for influenza (aOR: 2.25, 95 % CI: 1.08-4.68); and secondary/university education (aOR: 0.15-0.31) with no formal education as reference. For postpartum women, reasons for vaccination were perceived benefits for mother and infant, whereas not being offered vaccines was most cited for non-vaccination. Most prenatal care physicians recommended influenza vaccines during prenatal check-ups but believed vaccination causes flu-like symptoms.

CONCLUSION

Vaccination campaigns and provisions of free vaccines effectively increased knowledge and coverage among women in Costa Rica. To improve access, women should be offered vaccines during prenatal care appointments. Educating healthcare workers about vaccine benefits for themselves and patients is needed to mitigate safety concerns.

Narrative review on century of respiratory pandemics from Spanish flu to COVID-19 and impact of nanotechnology on COVID-19 diagnosis and immune system boosting

The rise of the highly lethal severe acute respiratory syndrome-2 (SARS-2) as corona virus 2019 (COVID-19) reminded us of the history of other pandemics that happened in the last century (Spanish flu) and stayed in the current century, which include Severe-Acute-Respiratory-Syndrome (SARS), Middle-East-Respiratory-Syndrome (MERS), Corona Virus 2019 (COVID-19). We review in this report the newest findings and data on the origin of pandemic respiratory viral diseases, reservoirs, and transmission modes. We analyzed viral adaption needed for host switch and determinants of pathogenicity, causative factors of pandemic viruses, and symptoms and clinical manifestations. After that, we concluded the host factors associated with pandemics morbidity and mortality (immune responses and immunopathology, ages, and effect of pandemics on pregnancy). Additionally, we focused on the burdens of COVID-19, non-pharmaceutical interventions (quarantine, mass gatherings, facemasks, and hygiene), and medical interventions (antiviral therapies and vaccines). Finally, we investigated the nanotechnology between COVID-19 analysis and immune system boosting (Nanoparticles (NPs), antimicrobial NPs as antivirals and immune cytokines). This review presents insights about using nanomaterials to treat COVID-19, improve the bioavailability of the abused drugs, diminish their toxicity, and improve their performance.

Maternal acute thermophysiological stress and stillbirth in Western Australia, 2000-2015: A space-time-stratified case-crossover analysis

BACKGROUND

The extreme thermal environment driven by climate change disrupts thermoregulation in pregnant women and may threaten the survival of the developing fetus.

OBJECTIVES

To investigate the acute effect of maternal exposure to thermophysiological stress (measured with Universal Thermal Climate Index, UTCI) on the risk of stillbirth and modification of this effect by sociodemographic disparities.

METHODS

We conducted a space-time-stratified case-crossover analysis of daily UTCI and 2835 singleton stillbirths between 1st January 2000 and 31st December 2015 across multiple small areas in Western Australia. Distributed lag non-linear models were combined with conditional quasi-Poisson regression to investigate the effects of the UTCI exposure from the preceding 6 days to the day of stillbirth. We also explored effect modification by fetal and maternal sociodemographic factors.

RESULTS

The median UTCI was 13.9 °C (representing no thermal stress) while the 1st and 99th percentiles were 0.7 °C (slight cold stress) and 31.7 °C (moderate heat stress), respectively. Relative to median UTCI, we found positive associations between acute maternal cold and heat stresses and higher risks of stillbirth, increasing with the intensity and duration of the thermal stress episodes. The cumulative risk from the preceding 6 days to the day of stillbirth was stronger in the 99th percentile (RR = 1.19, 95% CI: 1.17, 1.21) than the 1st percentile (RR = 1.14, 95% CI: 1.12, 1.15), relative to the median UTCI. The risks were disproportionately higher in term and male stillborn fetuses, smoking, unmarried, ≤19 years old, non-Caucasian, and low socioeconomic status mothers.

DISCUSSION

Acute maternal exposure to both cold and heat stresses may contribute to the risk of stillbirth and be exacerbated by sociodemographic disparities. The findings suggest public health attention, especially for the identified higher-risk groups. Future studies should consider the use of a human thermophysiological index, rather than surrogates such as ambient temperature.

Nonrespiratory sites of influenza-associated disease: mechanisms and experimental systems for continued study

The productive replication of human influenza viruses is almost exclusively restricted to cells in the respiratory tract. However, a key aspect of the host response to viral infection is the production of inflammatory cytokines and chemokines that are not similarly tissue restricted. As such, circulating inflammatory mediators, as well as the resulting activated immune cells, can induce damage throughout the body, particularly in individuals with underlying conditions. As a result, more holistic experimental approaches are required to fully understand the pathogenesis and scope of influenza virus-induced disease. This review summarizes what is known about some of the most well-appreciated nonrespiratory tract sites of influenza virus-induced disease, including neurological, cardiovascular, gastrointestinal, muscular and fetal developmental phenotypes. In the context of this discussion, we describe the in vivo experimental systems currently being used to study nonrespiratory symptoms. Finally, we highlight important future questions and potential models that can be used for a more complete understanding of influenza virus-induced disease.

Recent Advances in Plasma-Engineered Polymers for Biomarker-Based Viral Detection and Highly Multiplexed Analysis

Infectious diseases remain a pervasive threat to global and public health, especially in many countries and rural urban areas. The main causes of such severe diseases are the lack of appropriate analytical methods and subsequent treatment strategies due to limited access to centralized and equipped medical centers for detection. Rapid and accurate diagnosis in biomedicine and healthcare is essential for the effective treatment of pathogenic viruses as well as early detection. Plasma-engineered polymers are used worldwide for viral infections in conjunction with molecular detection of biomarkers. Plasma-engineered polymers for biomarker-based viral detection are generally inexpensive and offer great potential. For biomarker-based virus detection, plasma-based polymers appear to be potential biological probes and have been used directly with physiological components to perform highly multiplexed analyses simultaneously. The simultaneous measurement of multiple clinical parameters from the same sample volume is possible using highly multiplexed analysis to detect human viral infections, thereby reducing the time and cost required to collect each data point. This article reviews recent studies on the efficacy of plasma-engineered polymers as a detection method against human pandemic viruses. In this review study, we examine polymer biomarkers, plasma-engineered polymers, highly multiplexed analyses for viral infections, and recent applications of polymer-based biomarkers for virus detection. Finally, we provide an outlook on recent advances in the field of plasma-engineered polymers for biomarker-based virus detection and highly multiplexed analysis.

Effects of Vertical Transmission of Respiratory Viruses to the Offspring

Overt and subclinical maternal infections in pregnancy can have multiple and significant pathological consequences for the developing fetus, leading to acute perinatal complications and/or chronic disease throughout postnatal life. In this context, the current concept of pregnancy as a state of systemic immunosuppression seems oversimplified and outdated. Undoubtedly, in pregnancy the maternal immune system undergoes complex changes to establish and maintain tolerance to the fetus while still protecting from pathogens. In addition to downregulated maternal immunity, hormonal changes, and mechanical adaptation (e.g., restricted lung expansion) make the pregnant woman more susceptible to respiratory pathogens, such as influenza virus, respiratory syncytial virus (RSV), and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Depending on the infectious agent and timing of the infection during gestation, fetal pathology can range from mild to severe, and even fatal. Influenza is associated with a higher risk of morbidity and mortality in pregnant women than in the general population, and, especially during the third trimester of pregnancy, mothers are at increased risk of hospitalization for acute cardiopulmonary illness, while their babies show higher risk of complications such as prematurity, respiratory and neurological illness, congenital anomalies, and admission to neonatal intensive care. RSV exposure in utero is associated with selective immune deficit, remodeling of cholinergic innervation in the developing respiratory tract, and abnormal airway smooth muscle contractility, which may predispose to postnatal airway inflammation and hyperreactivity, as well as development of chronic airway dysfunction in childhood. Although there is still limited evidence supporting the occurrence of vertical transmission of SARS-CoV-2, the high prevalence of prematurity among pregnant women infected by SARS-CoV-2 suggests this virus may alter immune responses at the maternal-fetal interface, affecting both the mother and her fetus. This review aims at summarizing the current evidence about the short- and long-term consequences of intrauterine exposure to influenza, RSV, and SARS-CoV-2 in terms of neonatal and pediatric outcomes.

Comparison of clinical features and perinatal outcomes between pre-variant and post-variant periods in pregnant women with SARS-CoV-2: analysis of 1935 cases

Purpose

To compare the clinical features and perinatal outcomes of pregnant women with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the pre-variant and post-variant periods.

Methods

This prospective cohort study includes pregnant women with SARS-CoV-2 who were followed-up at Ankara City Hospital between 11, March 2020 and 15, September 2021. Demographic features, clinical characteristics and pregnancy outcomes were compared between the pre-variant (n = 1416) and post-variant (n = 519) groups.

Results

The rates of severe and critical cases significantly increased in the post-variant group (9.7% vs 2%, p < 0.001). The rates of respiratory support (26.8% vs 7.3%, p < 0.001), ICU admission (12.9% vs 1.8%, p < 0.001) and maternal mortality (2.9% vs 0.4%, p < 0.001) were significantly higher in the post-variant group. A significant increase was observed for pregnancy complications in the post-variant group (45.6% vs 18.8%, p = 0.007). The rates of preterm delivery (26.4% vs 4.4%, p < 0.001) and NICU admission (34% vs 18.8%, p < 0.001) were significantly higher in the post-variant group. Positive, weak, statistically significant correlations were observed between the post-variant period, disease severity and maternal mortality (r = 0.19, r = 0.12 and p < 0.001).

Conclusion

Post-variant COVID-19 period was associated with a severe course of the disease and increased rates of adverse obstetric outcomes in pregnant patients.

Comprehensive Overview of Vaccination during Pregnancy in Europe

Vaccinations during pregnancy can protect the mother from several infections, thus blocking vertical transmission. Furthermore, through passive antibody transfer, the newborn can be protected against some infections in the first months of life until their own vaccination regimen is initiated and completed at the appropriate age. Pregnancy can be considered a high-risk condition that increases vulnerability to infectious diseases with potentially unfavorable evolution. We present the current knowledge on vaccination during pregnancy in Europe as a useful information source for different health workers involved in prenatal care. Many European countries implement vaccination policies specifically designed for pregnant women, but there is great heterogeneity among programs. Recommendations on vaccination during pregnancy must be based on current high-quality scientific data. The decisions must be made for each individual case, depending on the associated conditions or special circumstances, with a concomitant assessment of the potential benefits and risks to both the pregnant patient and the fetus. Many vaccines are well-tolerated in pregnant women, with no clinically meaningful injection site reactions, systemic symptoms, or vaccine-related serious adverse events.

COVID-19 and miscarriage: From immunopathological mechanisms to actual clinical evidence

The association between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in the first half of pregnancy and pregnancy loss is still unknown. Infections by other coronaviruses, such as severe acute respiratory syndrome coronavirus (SARS-CoV) and the Middle East respiratory syndrome coronavirus (MERS-CoV), appear to increase the risk of miscarriage. The purpose of this study is to assess whether SARS-CoV-2 infection increases the risk of miscarriage. Firstly, a narrative review of the literature on animal and human studies was performed to analyze the immunopathological mechanisms of SARS-CoV-2 infection during preconception and early pregnancy, by which it may increase the risk of miscarriage. Secondly, a systematic review/meta-analysis of studies was conducted to assess the prevalence of miscarriage in COVID-19 patients diagnosed during pregnancy. Meta-analysis of proportions was used to combine data, and pooled proportions were reported. Seventeen case series and observational studies and 10 prevalence meta-analyses were selected for the review. The estimate of the overall miscarriage rate in pregnant women with COVID-19 was 15.3 % (95 % CI 10.94-20.59) and 23.1 (95 % CI 13.17-34.95) using fixed and random effect models, respectively. Based on the data in the current literature, the miscarriage rate (<22 weeks gestation) in women with SARS-CoV-2 infection is in the range of normal population. Well-designed studies are urgently needed to determine whether SARS-CoV-2 infection increases the risk of miscarriage during periconception and early pregnancy.

Neonatal outcomes after neuraminidase inhibitor use during pregnancy: A meta-analysis of cohort studies

AIM

Influenza infection poses a severe threat to pregnant mothers, and antiviral treatment is recommended. However, the safety of neuraminidase-inhibitor antiviral medications during pregnancy has not been well described.

METHODS

A systematic review and meta-analysis were performed to evaluate the adverse neonatal outcomes associated with exposure to neuraminidase inhibitors during pregnancy. The PubMed, Embase and Cochrane Library databases were searched to identify potential studies for inclusion.

RESULTS

Nine cohort studies that estimated adverse neonatal outcomes associated with exposure to neuraminidase-inhibitor medication during pregnancy were included. Exposure to a neuraminidase inhibitor during pregnancy was not associated with an increased risk of congenital malformation (odds ratio [OR] 0.9, 95% confidence interval [CI] 0.72-1.12, P = .341), low Apgar score (OR 0.96, 95% CI 0.77-1.2, P = .733) or preterm birth (OR 0.99, 95% CI 0.89-1.09, P = .771) compared with no exposure. However, exposure to a neuraminidase inhibitor was associated with a reduced risk of low birth weight (OR 0.79, 95% CI 0.68-0.92, P = .002) and giving birth to a small-for-gestational-age infant (OR 0.78, 95% CI 0.69-0.88, P < .001). Further analyses limited to oseltamivir exposure were consistent with the overall results.

CONCLUSION

Exposure to neuraminidase-inhibitor medication during pregnancy does not appear to be associated with adverse neonatal outcomes. We recommend further studies to investigate this association, which will help clinicians determine whether to prescribe a neuraminidase inhibitor during pregnancy.