Table 1.

Assessment of risk of bias

Authors	Peer reviewed?	Clearly focused study question?	Study design	Cohort recruitment acceptable? (Cohort, cross sectional studies)	Case control appropriate study method? (Case control studies)	Exposure (gestational age at birth) accurately measured?	Outcome (age at menarche/onset puberty) accurately measured?	Confounding factors identified?	Confounding factors accounted for?	Statistical summary measure given?
Atay et al.	Yes	Yes	Cross-sectional	Yes	N/A	Reported by parents	Self reported by participants or parents	Yes	No	No
Bhargava et al	Yes	Yes	Cohort	Yes	N/A	Not documented	Data from outpatient clinics	Yes	Yes	No
Chaudhari et al	Yes	Yes	Cohort	Yes	N/A	Not documented	Data from outpatient clinics	Yes.	Yes	No
D’Aloisio et al.	Yes	Yes	Cohort	Yes.	N/A	Self reported by participants or parents	Self reported by participants	Yes	Yes	Yes
Dossus et al	Yes	Yes	Cohort	Yes	N/A	Self reported by participants	Self reported by participants	Yes	No	Yes
Epplein et al	Yes	Yes	Cross-sectional	Yes	N/A	Calculated from date of LMP	Data from outpatient clinics	Yes	Yes	Yes
Ford et al	Yes	Yes	Nested cohort	Yes	N/A	Calculated from date of LMP and ultrasound measurements	Data from outpatient clinics	Yes	No	No
Hack et al.	Yes	Yes	Cohort	Control group recruited at 8 years of age	N/A	Calculated from date of LMP	Not documented	Yes	No	Yes
Hui et al.	Yes	Yes	Cohort	Yes	N/A	Calculated from date of LMP	Data from outpatient clinics	Yes	Yes	Yes
Kitchen et al	Yes	Yes	Cohort	No control group	N/A	Not documented	Data from outpatient clinics	Yes	No	No
Moisan et al.	Yes	Yes	Nested cohort	Yes	N/A	Reported by parents	Reported by parents	No	No	No
Peralta-Calcelen et al	Yes	Yes	Cross-sectional	Control group recruited in adolescence	N/A	Calculated from date of LMP and ultrasound measurements	Data from outpatient clinics	Yes	Yes	No
Persson et al.	Yes	Yes	Case control	N/A	Yes	Not documented	Data from outpatient clinics	No	No	Yes
Saigal et al	Yes	Yes	Cohort	Control group recruited at 8 years of age	N/A	Calculated from date of LMP and ultrasound measurements	Data from outpatient clinics	Yes	Yes	Yes
Sipola-Leppänen et al	Yes	Yes	Cohort	Yes	N/A	Calculated from date of LMP and ultrasound measurements	Data from outpatient clinics	Yes	Yes	Yes
Wehkalampi et al	Yes	Yes	Cohort	Yes	N/A	Not documented	Data from outpatient clinics	Yes	Yes	Yes