Table 1

Main characteristics of included studies

Authors, year	Country, year of participants’ enrolment	Study design	Affected/Non-affected	Gestational age at assessment	Type of pregnancy	Parity	Birthweight curve
Outcome: SGA <5th centile
Costet et al, 201231	France, 2002–2006 (PELAGIE cohort)	Nested case–control	134/399	11 weeks	Single pregnancy	Nulliparous and parous women, unclear proportions	Customised curve
Ertl et al, 201232	UK*	Nested case–control	150/1000	11⁺⁰–13⁺⁶ weeks	Unclear	55.3% nulliparous in SGA group, 48.1% nulliparous in control group	Population-based charts
Outcome: SGA <10th centile
Grandone et al, 200633	Italy*	Cohort	31/393	17.1±1.2 weeks† (mean)	Single pregnancy; no maternal pre-existing conditions	Unclear	Population-based charts
van Eijsden et al, 200839	The Netherlands, 2003–2004 (ABCD study)	Cohort	429/3275	13.5±3.3 weeks (mean)	Term deliveries, no diabetes or hypertension	57.6% nulliparous	Population-based charts
Horgan et al, 201117	Australia, 2008–2011 (SCOPE cohort)	Nested case–control	40/40	14–16 weeks	Single pregnancy; no other pregnancy complications	Nulliparous	Customised curve
Gernand et al, 201340	USA, 1959–1965 (Collaborative Perinatal Project)	Nested case–control	395/1751	≤26 weeks	Single pregnancy; term deliveries	Parous women	Population-based charts
Sulek et al, 201418	Singapore* (GUSTO study)	Nested case–control	41/42	26–28 weeks	Single pregnancy; term deliveries; no maternal pre-existing conditions	Nulliparous and parous women, unclear proportions	Population-based charts
Choi et al, 201634	South Korea, 2012–2013	Cohort	39/217	First, second or third trimester	Single pregnancies	Nulliparous and parous women, unclear proportions	Population-based charts
Kiely et al, 201635	Ireland, 2008–2011 (SCOPE cohort)	Cohort	190/1578	14–16 weeks	Single pregnancy; no maternal pre-existing conditions	Nulliparous	Customised curve
Ong et al, 201637	Singapore* (GUSTO study)	Cohort	83/827	26–28 weeks	Single pregnancy; no maternal chronic illness	43.5% nulliparous	Population-based charts
Wang et al, 201636	Taiwan, 2000–2001 (Taiwan Maternal and Infant Cohort Study)	Cohort	35/188	Third trimester	Unclear; term deliveries	48% nulliparous	Population-based charts
Delplancke et al, 201828	New Zealand*	Cohort	20/73	34–37 weeks	Unclear; term deliveries	Unclear	Customised curve
Luthra et al, 201838	USA, 2010–2012 (TIDES study)	Nested case–control	53/106	First and second trimester	Single pregnancies; term deliveries	60% nulliparous	Customised curve
Gong et al, 201841	UK, 2008–2012 (POP study)	Nested case–control	162/259	36 weeks	Single pregnancies; term deliveries	Nulliparous	Customised curve
Morillon et al, 201842	2008–2011 (SCOPE study)	Nested case–control	40/40	20 weeks	Single pregnancies	Nulliparous	Customised curve

*Unclear period of participant recruitment.
†Mean for all study participants.
ABCD, Adolescent Brain Cognitive Development; GUSTO, Growing Up in Singapore Towards healthy Outcomes; PELAGIE, Étude Longitudinale sur les Anomalies de la Grossesse, l’Infertilité et l’Enfance; POP, Pregnancy Outcome Prediction; SCOPE, Screening of Pregnancy Endpoints; SGA, small for gestational age; TIDES, Tackling Inequalities and Discrimination Experiences in health Services.