Inclusion criteria
Studies were initially identified based on their title and abstract and
later included after a full-text evaluation. Observational studies were
included if they met all of the following criteria: used a cohort study
design, explored whether maternal neuraminidase inhibitor use during
pregnancy increased the risk of adverse maternal or neonatal outcomes,
and had sufficient available data to allow the calculation of risk
estimates if adjusted data were not provided. Reviews, letters to the
editor, or conference abstracts; basic studies or those using animal
experiments; case reports or series; studies without a control group;
and studies that included other congenital malformations where it was
not possible to separate the data regarding oral clefts were excluded.
Data extraction and quality assessment Data were independently
extracted by two investigators, and any discrepancies were resolved by
the third author. The extracted information included author names,
publication date, study design, study location, study period, drug
exposure assessment results, outcome measures, statistical analyses
used, and study quality. The most-adjusted effect size estimate was used
when more than one estimate was provided. The risk of bias was estimated
using the Newcastle Ottawa Scale to assess the nonrandomized study
quality[14], as recommended by the Cochrane Collaboration. The risk
of bias concerning selection, comparability, and assessment of the
exposure/outcome was estimated according to nine items using a star
allocation scheme. The scale features eight criteria and yields scores
ranging from 0 (high risk of bias) to 9 (low risk of bias). Studies with
scores > 7 were considered high quality. Summary bias risk
assessments were derived for each study.