INTRODUCTION

Although in recent years there has been an increase of immigrants from Central America to southern countries of the Americas such as Chile, cross-border migration continues to have a major role in this process. In this regard, Peruvians are the main permanent migratory group in Chile, being 15.8% of all immigrants in the country ¹. Unlike other migratory groups, Peruvian migration is characterized by the large number of migrant women, most of whom are of reproductive age; for every 100 men, 107 women migrate from Peru ^{( 1}. Most of these women are incorporated into jobs such as domestic service under poor working conditions and tend to suffer social vulnerability. Likewise, many of them live in environments of social and institutional discrimination ². In this sense, it has been demonstrated that gender and migration are social determinants that affect women’s health ³, which becomes a more complex issue along with other determinants such as education, poverty, and job opportunities, in addition to other more specific ones such as access to and acceptability of health services ³.

In this scenario, reproductive health is even more relevant since gestation and childbirth are the main reasons for using health services among the immigrant population in Chile. Likewise, Peruvian women giving birth are the most frequent among immigrants in Chile ⁴.

In Chile, maternal health benefits are guaranteed by law for all pregnant women and immigrants, regardless of their migratory status ⁵. Women who migrate from Peru, like other cross-border groups, have gaps in the access to reproductive health care ². These access gaps are mainly due to convergent labor problems, bureaucracy, and lack of knowledge about the care system, all of which make access to care even more difficult. There are also interpersonal barriers, which are characterized by the perception of mistreatment and discrimination that affect the experience of women who migrate from Peru ².

These access gaps cause immigrant women to have a late entry into prenatal care, and less controls than the local population ⁶, which could affect their maternal and perinatal health ⁷. However, despite these gaps, there are studies that have reported better maternal-perinatal outcomes in the immigrant population in Chile ^{6 , 8}. This phenomenon is known as the “healthy immigrant effect”, which shows better health outcomes. However, this effect has been evaluated in migrants in general, without considering the particularities of each migrant group and the factors associated with it.

According to literature, the healthy immigrant effect is produced by a greater migration of young and healthy people, with better nutritional and health habits than the population of the receiving country ⁹. However, this effect is observed in different ways; there is evidence that it could be influenced by sociodemographic and economic aspects such as age, occupation, and the educational level of the immigrant population ¹⁰. In addition, morbid conditions concomitant with the pregnancy — mainly chronic and nutritional conditions such as anemia, obesity, hypertension, and diabetes — could have influence on the effect. These conditions could have a differentiated influence on the effect’s expression and are consistent with the stage of obstetric transition in the country of origin, reflecting indicators of maternal and perinatal morbidity and mortality and the causes associated with them ¹¹.

Additionally, it has been reported that the healthy immigrant effect can disappear after a long stay in the receiving country, because of an acculturation process. This concept is understood as a phenomenon that generates individual and population changes due to the adoption of habits and behaviors of the receiving culture ¹². This phenomenon generates epidemiological and demographic changes in the immigrants, who could assimilate the health problems of the receiving country; thus, affecting their maternal and perinatal health ¹².

Therefore, it is important to consider that Chile, as a receiving country, presents characteristics typical of a stage IV obstetric transition, such as low fertility rates, low maternal and infant mortality rates, high rates of obesity and chronic conditions ¹¹. Additionally, it presents low rates of maternal malnutrition, anemia, gestational pathologies, prematurity, and low birth weight ¹³.

Peru as a source of migrants and as a border country with Chile, is a country that remains in a stage III obstetric transition, with average fertility rates of two children per woman and a maternal mortality rate close to 299 maternal deaths per 100,000 live births ¹¹, as well as higher rates of maternal and perinatal pathologies, such as anemia, malnutrition, prematurity, low birth weight, etc. ¹⁴

The aim is to determine and compare maternal-perinatal characteristics and results between Chilean and Peruvian pregnant women living in the Metropolitan Region of Santiago de Chile, considering the differences in the epidemiological, obstetric, and perinatal profiles between both countries, and the fact that Peruvian migrants represent the main permanent immigrant population in Chile. Most Peruvian immigrants are women of reproductive age, have problems to access healthcare and are influenced by the healthy immigrant effect. Therefore, the purpose of this study is to determine if there is a difference in the populations under study and the potential factors associated with them. Our hypothesis is that Peruvian pregnant women have better maternal-perinatal indicators than Chilean pregnant women, and therefore express the healthy immigrant effect.

MATERIALS AND METHODS

RESULTS

Information was collected from 1,578 Chilean and 318 Peruvian women. The Peruvian pregnant women were residing in Chile for an average of 5.7 ± 3.2 years. The average age was statistically lower for Chilean pregnant women (26.6 ± 6.5) than for Peruvian pregnant women (28.1 ± 6.5) (p < 0.001). The proportion of pregnant women under 20 years of age (adolescents) was higher in Chilean than in Peruvian women (13.9% vs. 5.7%) (p < 0.001) (Table 1). The proportion of pregnant women over 35 years of age was significantly lower in Chilean than in Peruvian women (13.9% vs. 19.2%) (p = 0.015). Although there was no difference in the education level between the two groups, Chilean women had a higher proportion of women with less than 9 years of study (5.5% vs. 4.7%), and Peruvian women had a higher proportion of women between 9 and 12 years of study (72.5% vs. 74.2%).

Regarding the relationship status, Chilean pregnant women had significantly fewer partners than Peruvian women (70.5% vs. 84.7%) (p < 0.001). On the other hand, unemployment was significantly higher in Chilean women than in Peruvian women (60.2% vs. 52.4%) (p < 0.001). The lack of foresight was significantly lower in Chilean women (0.3%) than in Peruvian women (1.9%) (p < 0.001).

Regarding nutritional status (Table 2), Chilean women at the first prenatal control were 2.4 times more likely to be obese than Peruvian women, 32.8% vs. 16.4%, respectively. At the time of delivery, the obesity rate increased to 48.8% in Chilean women and 32.0% in Peruvian pregnant women, with Chilean pregnant women twice as likely to be obese as Peruvian women. The percentage variation in the obesity rate between admission to prenatal care and delivery in Chilean pregnant women was 48.9%, which means that the proportion of obesity in Chilean pregnant women increased by that percentage between both periods. On the other hand, the proportion of obese Peruvian pregnant women increased by 94.5% between the first prenatal control and delivery.

There was no difference between the obstetric variables analyzed regarding parity between pregnant women from both countries; multiparity predominated in both groups. Late admission to prenatal care was lower in Chilean women (40.5%) than in Peruvian women (59.5%) (p < 0.001). There was no difference between Chilean and Peruvian pregnant women regarding infectious and chronic maternal morbidity (Table 2). Regarding obstetric and perinatal outcomes (Table 3), there was no difference in cesarean sections between Chilean and Peruvian pregnant women, even though there was a lower rate for the latter.

The prevalence of GD was significantly higher in Chilean pregnant women than in Peruvian pregnant women (p < 0.001), in a 2:1 ratio, respectively. Obesity (AOR: 3.8, 95% CI: 2.44-6.18) and age < 20 years (AOR: 4.05, 95% CI: 2.25-7.29) were the variables most associated with GD in Chilean women (details of the A model not shown in Table 3). No statistically significant differences were found in PE or PPH.

Chilean pregnant women were less likely to present anemia during pregnancy than Peruvian pregnant women, which was observed in the adjusted model (AOR: 0.29, 95% CI: 0.18 - 0.47). Additionally, in the adjusted model we also observed that late entry to prenatal control was independently associated with anemia in Peruvian pregnant women (AOR: 0.43, 95% CI: 0.33-0.56).

Premature birth was almost three times more likely in Chilean than in Peruvian pregnant women, regardless of the adjustment variables.

LBW was three times more likely in Chilean women’s NB than in Peruvian women’s NB; obesity was the variable mostly associated to this condition in the adjusted model (AOR: 3.34, CI 95%: 2.33- 4.85). No statistically significant differences were found when comparing Chilean and Peruvian pregnant women in the presence of macrosomia, SGA and LGA.

DISCUSSION

In our study, we observed a demographic and nutritional difference between Chilean and Peruvian immigrant women, characterized by a higher average age in Peruvian women and higher unemployment in Chilean women. Additionally, a higher rate of obesity was found in Chilean pregnant women, which is consistent with previous studies carried out in Chile ⁶ and explains some adverse results observed in Chilean pregnant women. Although there were no major differences in the history of morbidity in women of both nationalities, the maternal and perinatal results we used to evaluate the effect of healthy immigrants on pregnant women who had migrated from Peru, support our hypothesis in most of the response variables studied.

Regarding maternal-perinatal outcomes, there was no difference between Peruvian immigrant pregnant women (PIPW) and Chilean pregnant women in the proportion of cesarean sections; the proportion in both groups was higher than what is recommended by the World Health Organization ¹⁹. However, the proportion of cesarean sections in pregnant Peruvian women (24.1%) was less than the 34% reported for Peru ¹⁴. The constant increase in the number of cesarean sections is a major public health challenge for both countries ¹¹. The similar rates in pregnant women from both countries could be explained by the length of the time of residence of the Peruvian pregnant women in Chile and by the similar epidemiological profile they have at the time of delivery ²⁰.

When it comes to obstetric morbidity, the possibility of GD was found to be greater in Chilean women, mainly associated with greater obesity, thus showing the effect of healthy migrant in this variable. This aspect is consistent with what is described in the literature, which shows that the increase in fatty tissue accentuates insulin resistance, with the consequent hyperinsulinemia and intolerance to carbohydrates, typical of gestational diabetes ²¹. However, despite being less likely to experience this condition, the prevalence of GD in pregnant Peruvian women was higher than what is described for Peru ²¹.

Additionally, the fact that the PIPW showed a significant increase in the proportion of obesity between entry to PC and delivery, along with a higher proportion of women over 35 years old, demonstrate that the epidemiological indicators for GD and obesity in this population are tending to be similar to those of the receiving country, as described in other studies on immigrants ^{9 , 22}. In this regard, it has been observed that the change of eating habits and lifestyles of migrants settled in urban areas, as well as the socioeconomic determinants, put them at greater risk of suffering from obesity and cardiometabolic diseases, which means that if the healthy immigrant effect disappears, they could become increasingly vulnerable to the mentioned conditions ²³.

Anemia was the only condition that was more prevalent in Peruvian pregnant women than in Chilean women. However, women in our study had half the prevalence of what is reported for Peru ²⁴. The association of anemia with late entry into prenatal care could indicate that the preventive strategies that favor early entry into prenatal care could decrease this condition in Peruvian pregnant immigrants ²⁵.

The healthy immigrant effect on PIPW was observed in most indicators for perinatal outcomes. The premature birth rate was less than half of what was found for Chilean pregnant women. The same effect happened with the percentage of low birth weight, which was less than the 8% reported for Peru ²⁶. The healthy immigrant effect has also been reported in studies carried out in the United States on Peruvian immigrants ²⁷ and on Latino immigrants in general ²⁸.

Maternal obesity emerges as an important variable to consider, especially given its association with gestational diabetes, premature birth, and low birth weight ²⁹. Thus, the underlying mechanisms involved in this association indicate that maternal obesity and gestational diabetes are associated with positive regulation of inflammation via increased production of adipokines by adipose tissue. In addition, the systemic secretion of pro-inflammatory cytokines increases, thereby contributing to premature delivery through endothelial dysfunction, insulin resistance and oxidative stress, which is associated with placental dysfunction, fetal malnutrition, and low birth weight ²⁹.

The low frequency of some morbidity indicators could be considered as a limitation of the study, possibly associated with the limited time for data collection. However, there was no statistical difference in these indicators.

In conclusion, the results of this study reflect that Peruvian pregnant immigrants in Chile experience the healthy immigrant effect, mainly regarding perinatal outcomes, and show better indicators than those reported in the literature for Peru ¹⁴. These aspects are also consistent with the fact that those who emigrate are in better health conditions ^{24 , 26}, which represents a potential improvement of demographic and health indicators for Chile as the receiving country.

However, it is necessary to promote intersectoral strategies of access and acceptability in prenatal care, to allow a preventive and curative approach to conditions such as anemia, as well as the promotion of healthy lifestyle habits to prevent obesity. To avoid the assimilation and acculturation processes, which imply the progression of Peruvian immigrant pregnant women to the morbid obesity profile of Chilean pregnant women. Finally, knowing that this population presents the healthy immigrant effect, encourages to take preventive and protective measures, to maintain and promote maternal and perinatal health.