Influxes of migrant women of childbearing age to receiving countries have made their perinatal health status a key priority for many governments. The international research collaboration Reproductive Outcomes And Migration (ROAM) reviewed published studies to assess whether migrants in western industrialised countries have consistently poorer perinatal health than receiving-country women. A systematic review of literature from Medline, Health Star, Embase and PsychInfo from 1995 to 2008 included studies of migrant women/infants related to pregnancy or birth. Studies were excluded if there was no cross-border movement or comparison group or if the receiving country was not western and industrialised. Studies were assessed for quality, analysed descriptively and meta-analysed when possible. We identified 133 reports (>20,000,000 migrants), only 23 of which could be meta-analysed. Migrants were described primarily by geographic origin; other relevant aspects (e.g., time in country, language fluency) were rarely studied. Migrants' results for preterm birth, low birthweight and health-promoting behaviour were as good or better as those for receiving-country women in >or=50% of all studies. Meta-analyses found that Asian, North African and sub-Saharan African migrants were at greater risk of feto-infant mortality than 'majority' receiving populations, and Asian and sub-Saharan African migrants at greater risk of preterm birth. The migration literature is extensive, but the heterogeneity of the study designs and definitions of migrants limits the conclusions that can be drawn. Research that uses clear, specific migrant definitions, adjusts for relevant risk factors and includes other aspects of migrant experience is needed to confirm and understand these associations.