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Preterm delivery among first-time Mexico-born mothers: a binational population-based comparison of deliveries in California and Mexico
  1. Sylvia Guendelman1,
  2. Dorothy Thornton2,
  3. Ricardo Perez-Cuevas3,
  4. Julia Walsh1,2
  1. 1Maternal and Child Health Program, School of Public Health, University of California, Berkeley, California, USA
  2. 2Division of Community Health and Human Development, School of Public Health, University of California, Berkeley, California, USA
  3. 3Division of Social Protection and Health, Inter-American Development Bank, Mexico City, Mexico
  1. Correspondence to Dr Sylvia Guendelman, Maternal and Child Health Program, School of Public Health, 207J University Hall, University of California, Berkeley, CA 94720-7360, USA; sylviag{at}


Background While studies have attributed the favourable birth outcomes of Mexico-born mothers in the USA to a ‘healthy immigrant effect’ that confers protection to immigrants, a comparison of immigrants with the source population in Mexico has been lacking. We compared preterm delivery (PTD) rates of Mexico-born immigrants who delivered in California with Mexico-born women who delivered in Mexico (WIMX) and with a subgroup who delivered in the five top immigrant sending states in Mexico.

Methods Using 2009 birth records, we selected all live-born singletons of primiparous WIMX (699 129) and immigrants in California (33 251). We examined the unadjusted and adjusted association between place of delivery and any PTD (<37 weeks gestation), including PTD subcategories (early, moderate, late), using relative risks (RR) and 95% CIs. Multivariate models controlled for demographic and health system characteristics.

Results PTD rates were higher among immigrants in California (6.7%) than WIMX (5.8%) and compared to women in the sending states (5.5%). The unadjusted risk of any PTD (RR=1.17 (1.12 to 1.22)), early/moderate PTD (<34 weeks gestation; RR=1.27 (1.18 to 1.38)) and late PTD (34–36 weeks; RR=1.14 (1.08 to 1.19)) was higher for immigrants than for WIMX and remained higher when controlling for age, education and healthcare variables. Birth weight <1500 g was also higher among immigrants (RR=1.27 (1.14 to 1.44)). Similar patterns were observed when comparing women in the sending states.

Conclusions We found no evidence of a ‘healthy immigrant effect’. Further research must assess the comparability of gestational-age data in Mexican and Californian birth certificates.

  • MCH
  • Health inequalities

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