2.1. Search strategy

The systematic review protocol, conduct and report, were executed in accordance with the criteria set out by the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines. ^{10 , 11} International prospective register of systematic reviews (PROSPERO) ¹² registration number: CRD42021275205.

We developed a search strategy with guidance from an academic liaison librarian and a Cochrane information specialist at St George's, University of London. The literature search was conducted on 7 December 2021 on three electronic bibliographic databases; MEDLINE, Embase, and Web of Science Core Collection. No time limit to the publication was set. The following search terms were used in different combinations: cytomegalovirus, CMV, shedding, excretion, replication, DNA, PCR, culture, seropositive, IgG, pregnant, and maternal. The search terms were adapted for use with the bibliographic database (full search strategy available under Supplementary Material).

The CoCoPop mnemonic (condition, context, and population) was used to determine the inclusion criteria ¹³ for the studies:

Observational studies including cohort, cross‐sectional and case‐control studies were included. Experimental studies, case reports, case series, review articles, full articles not in English, conference abstract and unpublished studies were excluded.

Identified studies were screened, deduplicated and catalogued on Mendeley Reference Manager. Title and abstract screening using the search strategy outlined above was performed independently by two‐blinded reviewers (S.S., A.T.) using Rayyan Qatar Computing Research Institute. The full‐text articles were also reviewed in a blinded manner by the same authors. Any disagreements were resolved through arbitration from the third reviewer (C.J.).