Salmon Bias and Preterm Birth Among Western Immigrants in China.

Introduction Immigrants from Western industrialized countries are rarely found in immigrant studies. Our primary objective was to calculate the rate of cesarean delivery, 5-min Apgar score <7, and preterm birth among Chinese and Western women. Our secondary objective was to examine whether there are significant differences in terms of risk factors between Western immigrants who chose to deliver in their country of citizenship compared to those who chose to deliver in China. Methods Single-center retrospective cohort study in Shanghai, China. Multivariate logistic regression models used delivery outcome, and place of delivery (China vs. country of citizenship) as outcome variables. Results Preterm birth occurred at a rate of 3.82% among Chinese citizens, 4.12% among Chinese-born Western citizens, and 6.54% among non-Chinese-born Western citizens. After adjustment, preterm birth <37 weeks was more frequent among non-Chinese-born Western citizens compared with Chinese citizens, with an odds ratio of 1.82 (Confidence Interval 1.20-2.78), p = 0.005. Variables statistically associated with giving birth in China were maternal age ≥35 years and being Chinese-born Western, as well as the absence of medical or obstetrical conditions. Discussion Western immigrants have overall good obstetrical outcomes in China, and this could be partly explained by selective immigration, but also by the Salmon bias, as women with risk factors tend to return to their country of citizenship for the delivery. However, the preterm birth rate was higher among Western women than in their Chinese counterparts, and further research is needed.

Vaginal birth after caesarean delivery in Chinese women and Western immigrants in Shanghai.

Recent studies show a steep rise in caesarean sections in China. Most couples are now eligible to apply for a second child. This retrospective cohort study compares the prevalence of trial of labour and vaginal birth after caesarean section among Chinese and foreign women in Shanghai. In total, 135 of 368 women underwent trial of labour (36.68%), and of those, 77 (57.04%) had a vaginal birth. After inclusion in a multivariate model, factors associated with trial of labour were maternal age <35 years with an adjusted odds ratio of 2.58 (1.49-4.46), absence of a history of ≥3 abortions (2.22 (1.08-4.57)), and European citizenship (1.94 (1.05-3.59)). The prevalence of trial of labour and vaginal birth seems to mirror rates found in countries of origin, but despite a high rate of caesarean section, Chinese women had a higher rate of vaginal birth after caesarean section than North American and Australian women, in particular. Impact statement What is already known on this subject: Caesarean section (CS) rates are rising worldwide. Repeat CS contributes largely to these rates, although vaginal birth after CS (VBAC) rates varies widely between countries. What the results of this study add: North American and Australian women who deliver in Shanghai have low rates of attempted trial of labour after CS (TOLAC) and VBAC, with European women having the highest rate of TOLAC, followed by Chinese women. Implications for clinical practice and/or further research: These findings might reflect different levels of acceptance in line with respective national trends. Studies evaluating the influence of cultural norms on birth preferences after CS are needed. Further research is also needed to assess the overall acceptance of TOLAC in the context of the softening of the one-child policy in China.