Do Anti-SARS-CoV-2 Monoclonal Antibodies Have an Impact on Pregnancy Outcome? A Systematic Review and Meta-Analysis

Monoclonal antibodies (mAbs) have been used as a rescue strategy for pregnant women affected by COVID-19. To explore its impact on maternal-fetal health, we included all observational studies reporting maternal, fetal, delivery and neonatal outcomes in women who underwent mAbs infusion for COVID-19. Primary outcome was the percentage of preterm delivery. We used meta-analyses of proportions to combine data for maternal, fetal, delivery and neonatal outcome of women treated with mAbs for COVID-19 and reported pooled proportions and their 95% confidence intervals (CIs) for categorical variables or mean difference (MD) with their 95% confidence intervals for continuous variables. Preterm birth was observed in 22.8% of cases (95% CI 12.9–34.3). Fetal distress was reported in 4.2% (95% CI 1.6–8.2). Gestational hypertension and pre-eclampsia were observed in 3.0% (95% CI 0.8–6.8) and 3.4% (95% CI 0.8–7.5) of cases, respectively. Fetal growth restriction was observed in 3.2% of fetuses (95% CI 0.8–7.0). Secondary prophylaxis with mAbs is currently considered the best treatment option for people with mild to moderate COVID-19 disease. More attention should be paid to infants born from mothers who were treated with mAbs, for the risk of immunosuppression.

The need to get the vaccine during pregnancy has been long debated, and many reports have been released on the scarce acceptance rates demonstrated by diverse populations of pregnant women worldwide [13][14][15][16][17], although the rate of obstetric complications was shown not to be different to unvaccinated women [18]. National and international societies have produced guidelines and recommendations, initially considering high-risk pregnancies as the main indications for the vaccine and proposing to include pregnant women into future vaccine trials, and then assessing that pregnancy should not be considered a contraindication to the vaccine [19].
At the end of 2020, according to the United States Food and Drug Administration (FDA, Silver Spring, MD, USA), monoclonal antibodies (mAbs) had become a therapeutic option for non-hospitalized subjects with mild to moderate disease, to prevent the risk of developing a severe form of coronavirus disease 2019 (COVID-19) [20]. Additionally, recent data showed a partial benefit even in hospitalized patients [21]. Given that SARS-CoV-2 infection can lead to cytokine storm and the formation of auto-antibodies, responsible for tissue and vascular damage, with eventual pro-thrombotic consequences at the placental level, the use of monoclonal antibodies could also be seen as an option to reduce auto-immune response against maternal and or placental tissues [22]. In the last several decades, the use of mAbs during pregnancy to treat chronic autoimmune diseases has been increasing. In fact, in case of relapse during pregnancy, both maternal and fetal outcomes worsen. Trans-placental passage varies depending on the specific drug structure, half-life, dose and timing of the last dose, according to gestational age [23]. Usually, transfer during the first trimester is determined only by diffusion across the placenta, and is in low amounts. Later, during the second and third trimester, mAbs are actively transported, with a high rate of transfer after 36 weeks. IgG1 is the most efficiently transferred [24]. At birth, mAbs levels are usually higher in the newborn than in the mother, and there is an inverse correlation between the last maternal dose and cord blood concentration [25]. Data on pregnancy outcomes derive from retrospective observational cohort studies with small sample size, but there is no report of increased adverse outcomes. The largest study is the PIANO study, which evaluated the outcomes of pregnant women with inflammatory bowel disease: the rates of congenital malformation, miscarriage, preterm delivery, low birth weight and infant infection were not increased compared with the nonexposed group [26]. However, there are other reports of association between mAbs and preterm birth risk, since it was shown that women treated with anti-tumor necrosis factors (TNFs) had a higher risk of preterm birth compared to their healthy control [27]. In addition, concerns were raised about the effects of in utero mAbs therapy and neonatal of infant consequences: cytopenia has been observed, although transiently, while rates of infections are still questioned, and the use of live attenuated vaccines is to be avoided until 6-12 months of age or whenever drug levels become undetectable [28].
It is noteworthy that the efficacy of mAbs against COVID-19 consists in linking directly to the receptor-binding domain of spike protein (through which the virus may be able to recognize and bind the angiotensin-converting enzyme-2 (ACE2) receptor and enabling the virus to enter human cells), reducing both the mortality and the morbidity risk, as well as the length of hospitalization [29,30]. As a result, although no clinical trials on mAbs included pregnant women for ethical reasons, the National Institutes of Health (NIH) guidelines declared that the therapeutic approach for pregnant women with COVID-19 should be the same as for non-pregnant women, whereas FDA gave a warning signal for pregnant and lactating women because mAbs actively cross the placenta, causing an early immunodepression in infants [31]. Overall, data about the safety of anti-SARS-CoV-2 mAbs during pregnancy are still scarce [32].
The aim of this systematic review is to perform a cumulative analysis of pregnancy outcomes after mAbs infusion for COVID-19, to better understand their impact in pregnant women.

Search Strategy and Eligibility Criteria
This review was performed according to a protocol recommended for systematic review. The study was reported according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines [33] and Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines [34]. PRISMA and MOOSE checklists are reported in the Supplementary Materials (Supplementary Materials Tables S1 and S2). The review was registered in PROSPERO (CRD42022356986) before the start of the literature search. The literature search was conducted using Web of Science, Scopus, ClinicalTrials.gov, MEDLINE, Embase, Ovid and Cochrane Library as electronic databases. The studies were identified with the use of a combination of the following search terms: "coronavirus" OR "COVID-19 pandemic" OR "SARS-CoV-2" OR "COVID-19" AND "monoclonal" OR "monoclonal antibody" OR "mAb" OR "mAbs" AND "pregnancy" OR "pregnant" OR "pregnant women" OR "during pregnancy" OR "pregnancy outcome" OR "fetal outcome" OR "adverse outcome" from 1 December 2019 to 12 August 2022.

Study Selection
All review stages were conducted independently by two authors. In particular, two authors (E.C., R.D.G.) independently assessed the electronic search, eligibility of the studies, inclusion criteria, risk of bias and data extraction; R.D.G. performed data analysis. All disagreements were resolved by discussion with senior authors (L.C., G.M.M.). Review of articles also included the abstracts of all references retrieved from the search. Duplications were removed using Endnote online software as well as manually. Only studies written in English were considered for inclusion. Unpublished or non-peer-reviewed studies were not included. Given that for ethical reasons no randomized controlled studies were planned in pregnant women, we included in our systematic review all retrospective studies and case series that evaluated the population of women receiving monoclonal antibody therapy against SARS-CoV-2 during the period of COVID-19 pandemic and evaluated pregnancy, maternal and fetal-neonatal outcomes.

Data Extraction and Risk of Bias Assessment
A data extraction sheet based on the Cochrane data extraction template for non-RCTs was used (https://dplp.cochrane.org/data-extraction-forms) (last accessed on the 15 August 2022). The main data extracted for our systematic review were: first authors' names and publication year, study design, study location, period considered in the analysis, sample size, inpatient or outpatient drug administration, type of intervention, vaccination for COVID-19, as well as various maternal, fetal and neonatal outcomes. Quality assessment of the included studies was performed using the Newcastle-Ottawa Scale (NOS) for casecontrol or cohort studies. According to the NOS, each study is judged on three broad perspectives: the selection of the study groups, the comparability of the groups and the ascertainment of outcome of interest. Assessment of the selection of a study includes the evaluation of the representativeness of the exposed cohort, selection of the non-exposed cohort, ascertainment of exposure and the demonstration that the outcome of interest was not present at the start of study. Assessment of the comparability of the study includes the evaluation of the comparability of cohorts based on the design or analysis. Finally, the ascertainment of the outcome of interest includes the evaluation of the type of assessment of the outcome of interest, its length and the adequacy of follow up. According to the NOS, a study can be awarded a maximum of one star for each numbered item within the Selection and Outcome categories. A maximum of two stars can be given for Comparability [35]. Case series were evaluated with a modified version of NOS [36], which is based on eight questions in the domains of selection, ascertainment, causality and reporting. Although a formal score could be assigned giving a binary response to each question, the numeric representation of methodological quality was not considered appropriate as recommended, and the overall final judgment was made based on questions 1, 2, 3, 7 and 8, which were deemed most critical in this specific clinical scenario (Supplementary Materials Table S3). We included case series/reports for which an adequate response to the abovementioned questions were found.

Data Synthesis
Outcomes were the evaluation of maternal, fetal, delivery and neonatal outcomes in pregnant women undergoing mAbs infusion. In particular, the primary outcome was the percentage of women who delivered preterm, defined as any birth before 37 completed weeks of gestation [37]. Other outcomes included the following: (1) adverse outcomes-adverse effect to infusion, fetal distress, gestational hypertension, pre-eclampsia, preterm premature rupture of membranes (pPROM), PROM, fetal growth restriction (FGR), cardiotocography (CTG) category III according to The International Federation of Gynecology and Obstetrics (FIGO) classification [38]; (2) delivery outcomes-preterm birth for COVID-19 maternal indication, full-term birth, vaginal delivery, operative delivery, urgent cesarean section, planned cesarean delivery, cesarean section, still pregnant; (3) neonatal outcomes-intensive care unit (ICU) admission, neonatal resuscitation, neonatal jaundice, neonatal death and 5 min Apgar < 7.

Statistical Analysis
We used meta-analyses of proportions to combine data. For categorical variables we reported pooled proportions and their 95% confidence intervals (CIs) for maternal, fetal and neonatal outcome of women treated with mAbs. For continuous variables, results were expressed as mean difference (MD) with their 95% confidence intervals. Data not reported as mean and standard deviation were transformed by appropriate statistical methods (e.g., by median and range) as described by Wan et al. [39]. All analyses were performed by adopting the random effect model of DerSimonian and Laird. Statistical heterogeneity among included studies was evaluated by the inconsistency index I2. In detail, heterogeneity was classified as null for I2 = 0%, minimal for I2 < 25%, low for I2 < 50%, moderate for I2 < 75% and high for I2 ≥ 75%. The analysis was performed using StatsDirect 3.0.171 (StatsDirect Ltd., Merseyside, UK) and Revman 5.3 (The Nordic Cochrane Centre, The Cochrane Collaboration, 2014) statistical software. A p value of <0.05 was considered significant.
Overall, these 17 studies included 190 pregnant women affected by mild to severe SARS-CoV-2 infection disease and treated with mAbs. The drug infusion was practiced at admission in the hospital for 81 patients and as outpatients for 105 other pregnant women. Hirshberg et al. [42] did not specify whether the treatment was administered as in-or outpatient for their four cases. Six studies included women also treated with anti-mRNA drugs for SARS-CoV-2 infection ( Table 1). The results of the quality assessment of the included studies using NOS and NOS modified scale are presented in Supplementary Materials Table S4. The included studies showed an overall good score regarding the selection and comparability of the study groups, and for ascertainment of the outcome of interest. Excluded studies and reason for exclusion are reported in the Supplementary Materials (Supplementary Materials Table S5).

Main Findings
We found that 22.8% of women affected by SARS-CoV-2 infection and treated with mAbs had a preterm birth. However, a large proportion of these deliveries were carried out for worsening maternal conditions, and not for adverse effects related to mAbs treatment. Indeed, 12.8% of patients experienced side effects and 36.9% of cases reported an adverse maternal, fetal and/or neonatal outcome. Regarding neonatal outcome, we consider that an increased rate of complication could be the direct consequence of preterm delivery itself.

Strengths and Limitations
The main strengths of the present systematic review include a thorough literature search aimed at including all potentially relevant studies, adherence to PRISMA and MOOSE guidelines, the inclusion of all different mAbs used for SARS-CoV-2 infection during pregnancy, as well as the inclusion of a wide spectrum of outcomes. The retrospective design of the included studies, the small sample sizes and their heterogeneity are the main limitations. However, it should be once again noted that data are still scarce, as pregnant women have not been included in any of the trials performed on monoclonal antibodies and COVID-19 to date. Unfortunately, we could not stratify by virus variant or for vaccinated and unvaccinated women for SARS-CoV-2. Despite these limitations, the present systematic review represents the most comprehensive and up-to-date critical appraisal on the safety and pregnancy outcomes following monoclonal antibodies therapy for COVID-19 disease in pregnancy.

Implications and Future Perspectives
Overall, this study showed that monoclonal antibodies against SARS-CoV-2 might be considered a useful therapeutic option for pregnant women. These findings are also supported by NIH, the American College of Obstetricians and Gynecologists (ACOG) and the Society of Maternal-Fetal Medicine (SMFM) recommendations [55][56][57]. In particular, NIH guidelines allow the use of tocilizumab in pregnant women, acknowledging that these patients should be considered as non-pregnant women. Patients should be eligible for mAbs if they present within 10 days of symptom onset, with mild to moderate COVID-19 symptoms [55].
There is evidence of an association between preterm delivery and use of mAbs in pregnancy: treatment with anti-TNF showed a higher risk of preterm delivery, while infliximab was observed in association to a higher risk of small for gestational age (SGA) in women with inflammatory joint and skin diseases [27]. Moreover, Jorgensen et al. found increased preterm birth rate for tocilizumab (31.1%) compared to the general population (10-15%) [58]. Nonetheless, although 22.8% of women in our pooled analysis had preterm birth, it should be noted that almost 30% of these deliveries were indicated for worsening COVID-19 maternal conditions and only one case of delivery shortly after infusion was reported [39]. Similarly, Sekkarie et al. [59] observed a preterm birth rate of 29% in their cohort of pregnant women affected by COVID-19. Furthermore, in studies where a stratification of preterm birth in pregnancies affected by COVID-19 has been performed, it has been observed that the rate of preterm birth seems particularly increased only after 34 weeks [60,61].
Therefore, the possible impact of the disease itself and its clinical form on the choice to deliver the baby should not be underestimated, since it could be a possible confounding factor for the association between preterm birth and mAbs treatment. Close to term, obstetricians could be more prone to deliver the baby, considering the lower rate of complication for late preterm deliveries compared to earlier preterm. Moreover, Sekkarie et al. [59] described only antivirals and systemic steroids as the main therapies used for pregnant women, but not mAbs. Hence, these retrospective data could eventually show association but not directly a causative effect, for which differently designed trials should be planned. In fact, keeping in mind that our pooled analysis considered mostly case reports, case series and cohort studies, we cannot confirm a proper association between adverse outcomes and mAbs infusion, which could have come out from prospective studies. We only compared pregnant women receiving mAbs with others not receiving this treatment. Levey et al. [52] found no difference in obstetrical outcomes apart from increased incidence of cesarean section in the control group, while Magawa et al. [53] found different placental weights, although no differences were observed among the fetal-neonatal outcomes. In addition, recent evidence showed that mAbs used for treatment of other diseases such as multiple sclerosis do not carry increased risk for adverse pregnancy outcomes, both compared to unexposed pregnant women affected by MS and the general population [62].
Another important concern regarding mAbs infusion during pregnancy, given the existence of the transplacental passage between mother and fetus, is regarding eventual neonatal immunosuppression. Jiménez-Lozano et al. described the reactivation of CMV 8 days after admission in a patient who received tocilizumab. The presence of CMV was confirmed by urine and blood analyses of the newborn [44]. To overcome or at least control this issue, as an example, multiple sclerosis treatments with mAbs during pregnancy are suggested until 32-34 weeks of gestation, with the advice to monitor newborns for the risk of immunodepression and cytopenia [63]. However, such considerations could be inapplicable to COVID-19-affected pregnant women, given that it is an acute condition, where the risk of worsening should be counteracted by prompt management and treatment. It could be argued that if a woman is affected by COVID-19 at term, the first option would be an urgent delivery of the fetus (e.g., by cesarean section), allowing more aggressive treatments once the woman is no longer pregnant. However, there could be cases in which the prognosis of SARS-CoV-2 infection would be uncertain, and therefore the choice to immediately deliver the baby or not could be difficult, and a prophylactic therapy would be of help in reducing the rate of progression to a severe form of the infection. A recent study observed no difference by trimester of diagnosis in the frequency of COVID-19 disease progression in pregnancy [64]. Certainly, more attention should be paid to infants born from mothers who underwent mAbs therapy because of the risk of immunosuppression. In this regard, debate is also ongoing regarding the timing of live infant vaccines in these neonates [31].
Further studies and evidence should stratify the pregnant populations treated with mAbs according also to the virus variant, since the Omicron variant appears to be more resistant to mAbs action than the Delta variant, and according to the vaccination status. In addition, more research will be needed to evaluate the overall efficacy, as pregnant women should also be included in clinical trials of such monoclonals.

Conclusions
In our meta-analysis, 22.8% of pregnant women delivered preterm, but a substantial percentage of these early deliveries were due to worsening COVID-19 symptoms. Although it seems that the risk for adverse pregnancy outcomes is not increased, more data and longer follow-ups are needed. More attention should be paid for infants born from mothers who underwent mAbs therapy because of the risk of immune suppression.

Supplementary Materials:
The following supporting information can be downloaded at: https: //www.mdpi.com/article/10.3390/vaccines11020344/s1, Table S1: PRISMA checklist; Table S2: MOOSE checklist; Table S3: Quality assessment of the included studies according to Newcastle-Ottawa Scale (NOS) for cohort studies; Table S4: Tool for evaluating the methodological quality of case reports and case series; Table S5: Excluded studies and reasons for the exclusion; Table S6: Adverse side effects observed in the included studies.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest:
The authors declare no conflict of interest.