Introduction

Arab ethnicity (AE) is associated with a lower risk for adverse birth outcomes compared with non-Hispanic Caucasians in both the USA1 and Europe.2 In the USA, it has been shown that persons with self-reported AE are 16% less likely than Caucasians to give birth prematurely.3 Understanding the determinants of adverse birth outcomes among groups with systematically better birth outcomes, such as Arab–Americans, might improve our understanding of the social risk factors for adverse birth outcomes in general. However, there is a relative paucity of research that has considered the determinants of adverse birth outcomes among Arab-ethnicity mothers (AEM).

El Reda and colleagues1 assessed the birth outcomes of AEM in Michigan. They found that among foreign-born AEM, pregnancy-related hypertension, diabetes and use of Medicaid to pay for hospital expenses were associated with preterm birth (PTB). Among native-born AEM, lack of prenatal care and pregnancy-related hypertension were correlates of PTB. El-Sayed and Galea4 showed that differences in rates of maternal marital status, tobacco use and foreign-birth between AEM and white mothers contributed to the association between AEM and lower risk for PTB compared with white mothers.

Cultural factors may be protective against adverse birth outcomes among AEM and may potentially explain some of the observed low risk of PTB among this ethnic group. Although there is no direct evidence to this effect among AEM, studies have linked cultural features to the birth outcomes of another ethnic group, particularly Hispanic-Americans. For example, in a prospective study of 1071 low-income, primiparous Mexican–American and African–American mothers, Zambrana and colleagues5 found that Mexican–American mothers were less stressed, less likely to abuse substances and more likely to have a positive attitude during pregnancy than their African–American counterparts. Upon controlling for these factors, the difference in risk for adverse birth outcomes between Mexican–American and African–American mothers was attenuated. The authors posited that Mexican culture protects against PTB and low birth weight (LBW) by promoting positive perinatal behaviours and a healthy maternal psychosocial status. Cultural factors have also been proposed as determinants of birth outcomes among other ethnic minority groups, including Samoans.11

As ethnic minority persons live and work in the USA and interact with the white majority, they acculturate.12 In doing so, they may acquire cultural features from the majority that may mitigate the protection against adverse birth outcomes afforded them by their original cultures. Suggestive evidence about the role of acculturation in the aetiology of adverse birth outcomes among ethnic minorities comes from studies about the birth outcomes of Mexican–Americans in the USA. Scribner and Dwyer13 used an acculturation scale to assess the relation between acculturation and risk for LBW. They found that highly acculturated Mexican–American women were at 1.86 times increased risk for LBW than their less acculturated counterparts. Several other studies have corroborated the association between acculturation and risk for adverse birth outcomes among this ethnic group.6–10 Moreover, Hyman and Dussault,14 assessing the relation between acculturation and risk for LBW, found that among five ethnic groups in Quebec, Canada, acculturation was associated with increased LBW risk.

Particularly relevant to our work, Peak and Weeks15 articulated a relation between community context, acculturation and birth outcomes among Mexican–Americans. They reasoned that if Mexican culture is protective against adverse birth outcomes among Mexican–Americans, then those living in Mexican enclaves in the USA should have a lower risk for adverse birth outcomes than their counterparts not living in these contexts because ethnic enclaves facilitate ethnic cultural practices and lifestyle. In a study of approximately 150 000 births in San Diego County, California, they found that Mexican–American mothers living in Hispanic ethnic enclaves were at a lower risk for LBW compared with those living outside such enclaves. Studies have also shown that Hispanic-Americans living in Hispanic ethnic enclaves are protected against other adverse health outcomes, including all-cause mortality,16 asthma17 and psychopathology.18 Pickett and colleagues19 demonstrated a similar effect among African–Americans. A study on birth outcomes among African–American mothers in Chicago in 1991 suggested that residence in areas with low African–American racial density was associated with increased risk for adverse birth outcomes.

Borrowing from the literature about the association between community context and the health and birth outcomes of Mexican–Americans, we used data from the state of Michigan, the state with the largest concentration of Arab–Americans in the USA, to assess the relation between maternal community context and risk for LBW among AEMs. We reasoned that if observations among Mexican–American populations are generalisable, we might expect that Arab–Americans living in areas of high Arab–American concentration would be less likely to be acculturated and hence to have a lower risk of adverse birth outcomes than Arab–Americans in areas less densely populated by members of their ethnic group. Therefore, we considered the relation between maternal residence in Dearborn, Michigan, the city with the largest Arab–American concentration in the USA20 and risk for LBW among AEM. We also considered the relation between maternal residence in the zip code with the largest proportion of AEM in Dearborn and risk for LBW among AEM. As a control, to ensure that any observable associations were not due to some other feature of the focal communities themselves, we replicated all analyses among non-Arab white mothers (NAWM) in Michigan.

Methods

Results

Complete data for analyses were available for 21 617 births to AEMs. Among women living in Dearborn who gave birth in Michigan between 2000 and 2005, 59.7% were AE. Of all zip codes in Dearborn, 48126 was the zip code with the highest proportion of AEM with 80.8% of the births between 2000 and 2005 in 48126 to AEM.

Table 1 shows the univariate statistics and bivariate χ² analyses between each of our covariates and LBW among AEM and NAWM, individually. Univariate statistics showed the following: overall, the prevalence of LBW was 6.5% among AEM and 6.8% among NAWM; 30.6% of all AEM in Michigan lived in Dearborn, while 0.7% of all NAWM in Michigan lived in Dearborn; 24.7% of all AEM lived in 48126 as compared with 0.2% of all NAWM.

In χ² models, residence in Dearborn (p=0.004) and 48126 (p<0.001) was associated with LBW among AEM but not NAWM. All other variables were associated with LBW among NAWM, but only parity (p<0.001), maternal age (p<0.001) and maternal birthplace (p=0.034) were associated with LBW among AEM.

Table 2 shows the multivariable regression models assessing the relation between covariates of interest (residence in Dearborn or residence in 48126) and LBW taking into account all other covariates among AEM. In separate multivariable models, residence in Dearborn (OR=0.85, 95% CI 0.75 to 0.97) and residence in 48126 (OR=0.81, 95% CI 0.71 to 0.93) were both associated with lower LBW risk compared with residence in the rest of Michigan.

Table 3 shows the multivariable regression models of LBW by residence in Dearborn or residence in 48126, and other covariates among NAWM. Neither residence in Dearborn nor 48126 was associated with LBW risk compared with residence in the rest of Michigan in multivariable models among NAWM.

Discussion

In a study of 21 617 births in Michigan between 2000 and 2005, we found that among AEMs, maternal residence in the city of Dearborn, Michigan, the city with the highest proportion of Arab–Americans in the USA, was associated with a 15% lower risk for LBW compared with maternal residence among Arab–Americans in the rest of Michigan. Moreover, among AEM, maternal residence in the zip code 48126, the zip code with the highest proportion of AEM in Michigan, was associated with a 19% lower risk for LBW compared with residence outside this zip code. Neither residence in Dearborn, Michigan nor residence in 48126 was associated with a lower risk for LBW among NAWM.

Although we know of no published studies that explicitly assess the effects of community context on the birth outcomes of Arab–Americans, our study does corroborate the findings of Peak and Weeks15 who assessed the effects of community context on the birth outcomes of Mexican–Americans in San Diego County, California. They found that residence in Hispanic enclaves was associated with a lower risk for LBW compared with residence in other localities among Mexican–American women but not among non-Hispanic white women.

Our finding that AEM in Dearborn were at lower risk for LBW than their counterparts outside this Arab–American-dense locality may be best interpreted within the broader framework of the acculturation-risk association for adverse birth outcomes among ethnic minorities.5–10 13 Ethnic enclaves are characterised by the cultural distinction they maintain from surrounding areas.21 Thus, ethnic inhabitants of these localities are more likely to maintain cultural features that may protect against adverse birth outcomes than their ethnic counterparts in other localities. Following this line of reasoning, it is possible that AEM in Dearborn, Michigan are less acculturated than their counterparts in other localities and that this difference in acculturation accounts for the findings documented here.

It is important to consider the following limitations when interpreting our findings. First, we used a limited covariate set. Of particular note, the only traditional socio-economic status variable that we included was maternal education; the paucity of socio-economic variables in our study could have allowed for residual confounding of the association between community context and risk for LBW among AEM. Second, our work is limited by the accuracy of birth-certificate data recorded in vital registry files. Although it has been shown that demographic data, including maternal ethnicity, from birth certificates is highly accurate, it has been shown that tobacco-use estimates in birth-certificate data can be unreliable.22–24 Third, although we hypothesise that relative acculturation may mediate the relation between community context and risk for LBW among Arab–American mothers, this cannot be verified with the data presented. It is also plausible that other factors, such as relative deprivation, may mediate the relation between community context and risk for LBW among this ethnic group.

Despite these limitations, our findings have several implications for future research. First, investigators interested in the relation between community context and the birth outcomes of Arab–Americans could assess the relation between community context and more specific birth metrics, such as PTB or intrauterine growth retardation. Second, investigators interested in the determinants of adverse birth outcomes among Arab–Americans might explore factors that may mediate the relation between community context and risk for LBW among AEM, such as metrics of acculturation or of relative deprivation. Third, investigators might consider neighbourhood-level studies that assess the relation between the concentration of Arab–Americans in neighbourhoods and risk for adverse birth outcomes among Arab–Americans in those contexts. Fourth, investigators interested in the health of Arab–Americans could consider the effects of community context on other health metrics among this ethnic group.