Pregnancy is one of the medical conditions listed in the Emergency Use Authorization (EUA) eligibility criteria for casirivimab/imdevimab (REGEN-COV). [1] This population has not been formally studied with either active ingredient. [1]

National Institutes of Health (NIH) endorsed guidelines on the use of anti-SARS-CoV-2 monoclonal antibodies states the agents "can be considered in pregnant people with COVID-19, especially those who have additional risk factors for severe disease. As immunoglobulin (Ig) G monoclonal antibodies, the authorized anti-SARS-CoV-2 monoclonal antibodies would be expected to cross the placenta. There is no pregnancy-specific data on the use of these monoclonal antibodies; however, other IgG products have been safely used in pregnant people when their use is indicated. Therefore, these products should not be withheld in the setting of pregnancy. When possible, pregnant and lactating people should be included in clinical trials that are evaluating the use of anti-SARS-CoV-2 monoclonal antibodies." [2]

According to the American College of Obstetricians and Gynecologists, no studies have evaluated monoclonal antibody regimens in pregnant population, and more data are required. They note pregnancy itself is associated with increased risk of COVID-19 clinical progression, making pregnancy status the only eligible risk factor for some patients to receive monoclonal antibodies at outpatient settings based on the EUA. Use of monoclonal antibodies may be considered by obstetric care clinicians to manage infections among non-hospitalized pregnant individuals, especially if one of the additional factors are present (BMI ≥30, chronic kidney disease, diabetes, cardiovascular disease). Equitable access to approved treatments is essential in communities with a high volume of COVID-19 infections. [3]

A 2020 meta-analysis examining biologics in pregnant women with inflammatory bowel disease (IBD) identified 48 studies (N= 6963 patients). They found adverse pregnancy outcomes among pregnant IBD women using biologics are comparable with that of the general population. [4]

Compared with other fully human monoclonal antibodies (adalimumab, infliximab), FDA Adverse Reporting System (FAERS) data show casirivimab and imdevimab have similar adverse reactions as other monoclonal antibody therapy. Data are limited with casirivimab and imdevimab with 11 cases reported in FAERS as of August 17th, 2021. Common adverse reactions reported were injection site reaction, pain, arthralgia, fatigue, and nausea.

Infliximab cases -- 156,950
Pregnancy cases: 2,363 (1.5%)
Adalimumab cases -- 243,265
Pregnancy cases: 4,896 (2%)

Data support that casirivimab and imdevimab adverse effects are similar to those above. Of reported cases in pregnant and perinatal patients, adverse effects of monoclonal antibodies showed the majority resulted in non-serious adverse effects or no outcome reported. Of note, some patients were hospitalized but it is unclear whether this was the result of monoclonal antibody treatment or pregnancy. [5]

There are insufficient data to evaluate a drug-associated risk of major birth defects, miscarriage, or adverse maternal or fetal outcomes. REGEN-COV (casirivimab and imdevimab) should only be used during pregnancy if the potential benefit outweighs the potential risk for the mother and the fetus. [6]

Nonclinical reproductive toxicity studies have not been conducted with casirivimab and imdevimab. In a tissue cross-reactivity study with casirivimab and imdevimab using human fetal tissues, no binding of clinical concern was detected. Human immunoglobulin G1 (IgG1) antibodies are known to cross the placental barrier; therefore, casirivimab and imdevimab have the potential to be transferred from the mother to the developing fetus. It is unknown whether the potential transfer of casirivimab and imdevimab provides any treatment benefit or risk to the developing fetus. [6]

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. [6]