### Supplementary Materials for **Maternal Work and Children’s Development: Examining 20 Years of Evidence** By Maria C. Lo Bue, Elisaveta Perova and Sarah Reynolds

# 1. Methods

## 1.2 Search

To identify previous studies, we first listed search terms determined from an informal scoping review: we considered the main types of outcomes researched and used the authors’ knowledge of common realms of outcomes in the child development. (All authors had published on this topic previously.) The following three sets of search terms emerged: “Maternal” OR “Mother”; “Work” OR “employment” OR “labor”; and “child development” OR “health” OR “nutrition” OR “obesity” OR “stunting” OR “wasting” OR “underweight” OR “overweight” OR “behavior” OR “socio-emotional” OR “cognition” OR “schooling” OR “education” OR “illness” OR “asthma accident”.

In October 2021 a research assistant used the 104 search term permutations to collect citations from EconLit and Web of Science.<sup>5</sup> From this list, we selected the top three permutations with the most results and searched them in PubMed. This search did not provide additional documents to include in the review, so we did not continue with the full search in PubMed. We did find some additional citations using this approach with PsychInfo, so we also repeated the citation search using this database. We compared the citations from our search to the citations included in the systematic review by Lucas-Thompson, Goldberg, and Prause (2010). As a result, we added the additional search terms “outcomes” OR “achievement” OR “adolescent” OR “adolescence,” which increased our total to 1182 records. Duplicates were removed, reducing our total to 614 records.

Titles were screened for topic relevance by a research assistant and one author of this review. We excluded studies focusing on samples of children with disabilities from birth, premature children, or teen mothers. We excluded outcomes on usage of health services (i.e., vaccinations, nutrition related behaviors, doctor visits). Similarly, we excluded outcomes that are considered mediators leading to the final outcomes in our list (e.g., dietary intake, sedentary behaviors, sleep, work-family conflict). We excluded employment relating to migration or sex work. This screening provided us with 313 records.

For the final decision regarding inclusion, the abstracts and/or methods sections of papers were examined by an author of this review, with the other authors consulted regarding the empirical quality of the studies. We limited the studies to those published between 2002 and 2021. Studies were included if they had quantitative analysis, a measure of maternal work as a causal variable in the paper, at least one child or adolescent development outcome (cognition, schooling, behavior, anthropometrics, and health). Moreover, we restrict the analysis to studies analyzing natural or quasi-natural experiments and using the following methodologies: individual fixed or random effects, lagged dependent variables,<sup>6</sup> sibling fixed

> 5 The search was restricted to the titles of articles, since when the entire content of the articles was searched, it returned tens of thousands of papers. Several keyword searches (in contrast to title searches) of the permutations that yielded the most results did not provide additional papers for the review, so we did not pursue a keyword search.

6 Even though many papers analyzed longitudinal data on maternal work, we excluded studies that only controlled for observables. One exception is the lagged dependent variable approach, which controls for the baseline value of the outcome variable. Although the lagged outcome variable is an observable, including it accounts for unobserved maternal or child characteristics that affected the earlier outcome, which reduces selection bias due to unmeasured child and family characteristics. However, if the study had controls for child development measures at baseline and these were from the same realm as the outcome variable, even if not exactly the same measure, we 10