pcb Ludvigsson 2013.

Methods	Retrospective cohort study. Pregnancy outcomes were compared between women exposed to Pandemrix (monovalent H1N1 pandemic‐AS03‐adjuvanted influenza vaccine) during pregnancy and non‐exposed women.
Participants	All live‐born single infants in Stockholm County (conceived between February 2009 and January 2010, n = 21,087)
Interventions	Exposure to 1 dose of monovalent pH1N1‐AS03‐adjuvanted influenza vaccine (Pandemrix) at any time during the pregnancy before the 36th week. Records of vaccination are available from Vaccinera database (vaccination campaign was performed between October 2009 and April 2010, thus about 90% of the doses were administered before end of 2009). In total, 13,297 women were vaccinated against H1N1 during pregnancy before the 36th week. The non‐exposed hemi‐cohort consisted of women who did not receive influenza vaccination during pregnancy or who were immunised after the 36th week (n = 7790). Different times of exposure during pregnancy (1st or 2nd ‐ 3rd trimester) were also considered for analysis.
Outcomes	Data about pregnancy outcomes were available in the Obstetrix database, in which information from the 1st antenatal visits (8 to 12 gestation weeks) until discharge are collected. For each participant a record is available that can be identified by means of a unique identifier (PIN), which permitted the link between Obstetrix data and those recorded in other archives (Vaccinera among others). Birth weight < 2500 g Gestational duration < 37 weeks Small for gestational age Apgar score at 5 min < 7 Caesarean section
Notes	Funding source ‐ government This project was supported by grants from the Swedish Research Council (Medicine), and the Swedish Council for Working Life and Social Research (FAS). JFL was funded by the Swedish Research Council (Medicine), OS was funded by the Swedish Society of Medicine. LR was partially supported by grants from the Compagnia san Paolo/Firms and the Italian Association for Cancer Research.
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ selection exposed cohort All outcomes	Low risk	The whole birth cohort of infants conceived between February 2009 and January 2010 in Stockholm, Sweden, whose mother received the influenza vaccine during pregnancy
PCS/RCS ‐ selection non‐exposed cohort All outcomes	Low risk	The whole birth cohort of infants conceived between February 2009 and January 2010 in Stockholm, Sweden, whose mother did not receive influenza vaccine during pregnancy
PCS/RCS ‐ comparability All outcomes	Unclear risk	All possible confounders have been taken into account.
PCS/RCS ‐ assessment of outcome All outcomes	Low risk	Secure records
Summary assessment	Unclear risk	Unclear risk of bias