The study aimed at identifying factors associated with low birth weight over 5 years in a mid- sized city in São Paulo state interior region, Brazil, and expanding the discussion about this theme in the literature. For that purpose, a control group was set up to compare variables and search different data sources for a joint discussion about maternal socio-demographic factors, those related to delivery and to the newborn and in a highly comprehensive manner, the prenatal care provided for these pregnant women.
Data and outcomes from this study revealed the reality of the city in the study years concerning characterization of low birth weight newborns, their conditions of prenatal follow-up and birth as well as maternal health and socio-demographic situation, considering that the study analyzed the world of the LWNB and used a sample, for technical feasibility, of non-low weight NB as a control group so that the comparison between them was made.
Low birth weight rate for the city of Botucatu has been higher, except for the year 2008, than the rates for São Paulo state [17], the South (8.7%) and the Southeast region (9.1%) and it has been higher than the rates found for less developed regions in the country (North 7.0% and Northeast 7.4%) [18].
Currently, reduction in these regional disparities in Brazil has been attributed to prematurity rates, which have been increasing in the country as a whole, and kept low rates of birth weight. Simultaneously, in the last decade, a reduction in term children with low birth weight (intrauterine growth restriction) has been observed. Therefore, low birth weight has been associated rather to conditions of access to health care and services than to socio economic conditions [30].
In this study, factors associated with low weight were prematurity, twin births, maternal malnourishment and obesity, inadequate weight gain less than 5 kilos or more than 15 kilos and maternal smoking. Considering the reality in which the study was conducted, i.e., in a city with good socio-economic conditions, a good score in the HDI classification [24], high level of maternal schooling and low rate of illiteracy, these variables and maternal age were not associated with higher risk of LBW. These findings are in agreement with those reported in some studies conducted in Brazil and in other countries [14, 31, 32].
Therefore, no conclusions can be reached on the association between socio economic and demographic conditions and LBW. This finding is a consequence of different socio economic realities in the study regions, since they are interconnected factors related to life conditions of the population such as, housing, income, basic sanitation, level of knowledge and access to health services which directly influence favorable or unfavorable outcomes in the health-disease process, including pregnancy and birth conditions.
A stronger association of LBW with prematurity and not with intrauterine growth restriction is pointed out in this study. Also, twin pregnancies are often associated with shorter period of gestation. The association has already been described in Brazil and worldwide, and currently it has been considered the main factor for keeping low birth weight rates in Brazil [2, 30, 33].
The importance of maternal smoking during pregnancy and its relationship with low birth weight is reported in the literature and also confirmed in this study as an important predictor of LBW. This finding was one of the first consequences of this habit, and it is probably related to intrauterine hypoxia leading to fetal malnutrition [34, 35]. Some studies in United States and Canada have reported that smoking reduction during pregnancy may decrease the LBW incidence in developed countries like USA and Canada [36, 37].
The infant mortality rate of the Low Birth Weight newborn group in our study shows the local reality and represents 60 deaths per 1000 births. No deaths were reported in the control group. However, data analysis from the SEADE Foundation [22], which reports IM rates and number of deaths per year in the city, revealed a rate of 0.7% for this population, that is, 7 infant deaths per 1000 births. The low value obtained in this study for the Apgar score at 5 minutes, mostly in the LBW group, could be associated with the higher frequency of infant deaths in this group of NB. Neonatal depression maintained at 5 minutes in Apgar score represents maintenance of adverse conditions with consequences for the prognosis of these NB who have already been compromised by inadequate birth weight and short gestational age. Also, it contributes to higher rates of neonatal mortality [38].
Maternal nutritional status and weight gain during pregnancy have been addressed in many studies. According to Melo et al. [39] "not only to the growing prevalence of their disorders but also to their important role in gestational outcomes, such as fetal growth and birth weight [...]". A reduction in calorie intake during pregnancy because of distinct reasons is the cause of low birth weight in NB, and the literature on this issue is historical and ancient. Low weight gain causes serious harm and may account for higher morbimortality rates of these NB. The most used concept of adequacy, even in this study, has been the one which considers adequate weight gain as 10 to 15 kg [40–42].
Many researchers have evaluated the association between previous maternal diseases and gestational diseases and low weight of newborns [35, 43]. Some studies reported a reliable association among them. However, other studies in the literature and also the present study found a different association. In this study, an initial positive association between LBW and some diseases (systemic and gestational hypertension and gestational diseases) was observed, although it was not verified in the multivariable analysis.
For the city of Botucatu, which has a diversified public health care both in Basic Health Units (BHU) and in the Public University Hospital, as well as good level of maternal schooling, the situation mentioned above is an expected reality considering that pregnant women awareness and the access to health services ensure them an adequate disease control.
The Public Health System in Brazil follows organizational principles, and the hierarchical health care is one of them. [44] The referral to services which require advanced technology and more expertise must be done in cases in which the health primary attention has identified them as at higher risk. Based on our findings, it could be observed that this organizational system of SUS has appropriately led to a higher number of LWNB deliveries in the public University Hospital. This demand for services with high level of technology rises the cost of health care in the Brazilian Public Health Service, which is a universal system funded by taxes and specific contributions [45]. In addition, higher occurrence of cesarean deliveries in this group of NB as compared to that in the adequate weight group was found, which justifies both situations, place and type of delivery, since these NB and their pregnancies are at higher risk as a consequence of maternal or fetal complications at birth. The place of delivery could be justified as a search for better perinatal outcomes, since University Hospitals, with characteristics of tertiary care, offer adequate support for neonatal care (neonatal ICU) usually required by these NB [46].
Data from Brazil show that there have been high coverage rates for prenatal follow-ups with 80.7% of women having 5 or more prenatal consults between 2006 and 2007, and 83.6% of them, starting the prenatal follow-up within the first trimester of gestation. Therefore, the present concern relies on quality evaluation of the care provided.
A high coverage rate for prenatal care was also observed in our study, which shows the appropriate understanding of the need for follow-ups by the pregnant women. Moreover, it shows the wide offer of this service in the health care system.
Prenatal care is one of the most ancient care practice in the Brazilian Health System, and an optimal condition would be the one in which medical care could be offered to women since the very beginning of the pregnancy diagnosis. For that purpose, health services must have skilled professionals to appropriately welcome and build close ties with the users. Therefore, the main determinant of low quality care provided by the SUS network has been the limited human resources. However, this limitation is qualitative rather than quantitative [47].
Care of pregnant women must include minimal procedures and necessary exams to reduce maternal and fetal morbidity and mortality. This care would be through prevention and early diagnosis of alterations as intrauterine growth restriction and maternal infections which can be vertically transmitted to the offspring [42]. A good prenatal follow-up ensures a protective effect for the pregnant woman and fetus through better nutritional control, access to resources for reducing smoking, and early diagnosis and adequate treatment of infections and diseases which could prevent low birth weight in newborns.
According to some studies, neonatal mortality, prevalence of low birth weight and prematurity in Brazil are related to lack of access to routine and basic procedures concerning pregnancy assistance [13].
One of the objectives of this study was to evaluate prenatal care and its relationship with low birth weight. The modified Kessner Index, Adequacy Prenatal Care Utilization Index and Kotelchuck Index are combined measurements more frequently used to a better study of quality of prenatal care utilization [25, 26]. The criterion used to evaluate quality of prenatal follow-up is essential, and the more complex and comprehensive it is, the better the identification of the reality in which the study took place, enabling data collection for discussion about the care delivered. This study revealed a reduction in the adequacy indexes for both groups according to the increase in coverage of the indicator used.
The increase in inadequacy as a result of the modified Kessner Index utilization, as compared to the analysis which considered only the number of visits at the gestational age, shows that the late start of prenatal follow-up was the contributing factor in this reduction in adequacy.
Therefore, when variables are associated for a judicious evaluation of prenatal quality, different results are found compared to those from a more partial or fragmented analysis of care, even when there is no association with LBW as in the present study.
Attention to adequate prenatal care should not be limited to prevention of LBW, as this service ensures advising for pregnant women concerning their health, and adoption of healthy life habits for themselves and their infants. Moreover, it identifies risk situations for pregnancy and delivery, interventions are timely applied and unfavorable outcomes for the mother or newborn are avoided. Also, mothers may be enrolled in programs of health care attention to the woman and infant for later follow-ups.
Data from this study and from literature show that the risks for LWNB are fully established and they may vary according to the social and economic reality in which the study was conducted. However, this problem must be acknowledged and faced by the Health Public System. Although the widespread knowledge of the risk for low birth weight in Sao Paulo state and Brazil, the specific evaluation of the prenatal follow-up and control of these factors have not been widely and uniformly performed in Brazilian cities. The adequate identification of LBW associated factors must create effective and preventive strategies, and the birth of LWNB must give rise to a necessity of redesigning intra and extra hospital actions to better welcome and follow the triad of the NB/mother/family, reducing risks and promoting better growth and development of this infant.
Few limitations were found in this study, as for the object of the study (LBW), all cases in the study period were included. The proposal of identifying prenatal care associated factors and considering births within the Public Health System led to the incorporation of most pregnancies and births occurred in the city. However, because of the great population diversity, the study of prenatal care in private or managed health care settings could bring other contributions to the discussion of this issue.