Population-based reference for birth weight for gestational age in northern China

Background Localized birth weight references for gestational age serve as an essential tool in accurate evaluation of atypical birth outcomes (e.g. small for gestational age) in clinical diagnosis and region-specific epidemiological studies. Such standards are currently not available in Mainland China. Aims To construct up-to-date, sex- and parity-specific birth weight references based on 231,937 births in Taiyuan, China during years 2005–2011. Study design Population-based, cross-sectional. Subjects Hospital-registered, healthy infants with births dated between 11/01/2005 and 12/31/2011 within Taiyuan area. Outcome measures Birth weight in grams, and gestational age in complete weeks were calculated using a combination of last-menstrual-date-based estimation and ultrasound examination. Results Separate birth weight references are constructed for male and female infants born from primiparous and multiparous mothers. Male infants are found to weigh more than female infants in later gestational ages (appr. weeks 33–42), and infants born to multiparous mother are found to weigh more than infants born to primiparous mothers in later gestational ages (appr. weeks 36–42). Conclusions The Taiyuan birth weight reference curves display similar trends of growth as reference curves from other countries worldwide (Netherlands, Scotland, Australia, Canada, Hong Kong, Korea and Kuwait). However, growth of birth weight for Taiyuan infants tends to be slower compared to European and North American infants regardless of gender, but similar to infants from other Asian countries.