Print version ISSN 0034-8910
Rev. Saúde Pública vol.35 no.6 São Paulo Dec. 2001
Estado nutricional de gestantes: prevalência e desfechos associados à gravidez
Luciana Bertoldi Nuccia, Maria Inês Schmidta, Bruce Bartholow Duncana, Sandra Costa Fuchsa, Eni Teresinha Fleckb and Maria Margarida Santos Brittoc
aDepartamento de Medicina Social da Faculdade de Medicina da Universidade Federal do Rio Grande do Sul. Porto Alegre, RS, Brasil. bCentro de Ciências da Saúde da Universidade de Fortaleza. Fortaleza, CE, Brasil. CFaculdade de Medicina da Universidade Federal da Bahia. Salvador, BA, Brasil
According to the World Health Organization (WHO), the increased frequency of obesity in many countries can be characterized as a pandemia of major public health concern.13 Maternal nutritional status is an important determinant of pregnancy outcomes since prepregnancy underweight has been traditionally considered a risk factor for adverse gestation outcomes.3 Obesity also increases pregnancy complications, such as gestational diabetes, hypertensive disorders, and perinatal morbimortality.12
Brazil is a heterogeneous country regarding its population characteristics, and health problems of pre-obesity and obesity coexist with undernutrition. Recent trend analyses of nutritional status have placed the problem of obesity squarely on the Brazilian public health agenda.8
The objective of the present study was to assess prepregnancy nutritional status among women seen in prenatal clinics of the Brazilian national health system, its population correlates and its associated adverse pregnancy outcomes.
The study was conducted in prenatal care clinics of the national health system (Sistema Único de Saúde ¾ SUS) of six state capitals in Brazil, between 1991 and 1995. A cohort of 5,564 consecutive women aged 20 years and more, otherwise non-diabetic, were followed from about weeks 20-28 of gestationtill delivery. Analysis was carried out for 5,314 women, as in 250 there was a lack of information required to calculate prepregnancy body mass index (BMI).
At enrollment, a standardized questionnaire provided information on age, prepregnancy weight (in kilograms), years of education, and parity. Maternal height was measured in duplicate and recorded in centimeters according to the standard protocol. Skin color was subjectively assigned. Prepregnancy nutritional status was classified based on BMI, according to the World Health Organization (WHO) criteria: underweight (BMI<18.5 kg/m2), normoweight (18.5 kg/m2 £ BMI <25 kg/m2), pre-obesity (25 kg/m2 £ BMI< 30 kg/m2), and obesity (BMI³30 kg/m2). Women who fall in the latter two categories were also characterized as overweight.13
Gestational diabetes mellitus was defined according to the current WHO criteria as fasting plasma glucose of at least 7.0 mmol/l or a 2-hour-post 75g glycemia of at least 7.8 mmol/l.14 Gestational age was characterized according to hierarchical criteria based on four clinical examinations: ultrasound before week 26 in 52% of the sample; ultrasound after week 26 consistent with neonatal age estimation or last menstrual period in 15%; reported last menstrual period consistent with neonatal age estimation or uterine height in 23%; and neonatal age estimation, ultrasound after week 26, uterine height, or last menstrual period in the remaining 10%. Macrosomia was defined as birth weight at or above the 90th percentile for the gestational age of the study sample; microsomia was defined as birth weight below the 10th percentile for the gestational age. Hypertensive disorders were ascertained through chart review and classified according to the National High Blood Pressure Education Program Working Group. Pre-eclampsia (hypertension after week 20 of gestation associated with proteinuria or seizures) included only cases of new onset hypertension.
Frequencies of underweight, pre-obesity and obesity ¾ and their 95% confidence intervals ¾, both crude and adjusted, are displayed, the latter obtained through logistic regression.11,15 Odds ratios for pregnancy outcomes were also calculated using logistic regression. Statistical analyses were performed using the statistical software SAS.
The Ethical Committees of the Institutions approved the study protocol, and participants signed the study consent.
Table 1 shows the distribution of characteristics of 5,314 women included in the analysis and of those excluded due to missing information. Inability to calculate prepregnancy BMI was more frequently seen among multiparous women with lower educational level and miscellaneous skin color in the Salvador center.
Age specific prevalences of prepregnancy nutritional status are presented in Table 2. Prevalences of underweight decreased in the age groups from 9% for women aged 20 to 24 years to 3.4% for those 30 years and more. In contrast, for pre-obesity and obesity, prevalences increased with age. Overall age-adjusted prevalences (95% CI) based on prepregnancy weight were: underweight 5.7% (5.1%-6.3%), pre-obesity 19.2% (18.1%¾20.3%), and obesity 5.5% (4.9%-6.2%) (p<0.001).
Table 3 describes age-adjusted prevalences (95% CI) of prepregnancy nutritional status, according to study center, educational level, skin color, and parity. Although the Salvador center had the highest prevalence of underweight, the obesity prevalence in this center was also high. Overweight was more frequent in study centers in the more industrialized south and southeast regions (Porto Alegre, São Paulo, and Rio de Janeiro) (p<0.001). Porto Alegre and Rio de Janeiro showed the highest adjusted frequencies for obesity. Educational level was inversely related to nutritional status, obesity being more prevalent among less educated women (p=0.03). Overweight was commonly seen among black women, and obesity was more prevalent in black than in white or miscellaneous skin color women (p=0.01). Nulliparous women presented a different nutritional status distribution than multiparous ones, the age-adjusted prevalence of underweight was higher and pre-obesity and obesity was lower than among parous women. Those having three or more previous pregnancies had higher age-adjusted prevalence of obesity (p=0.002).
Table 4 demonstrates an inverse association of nutritional status and microsomia. Pre-obese and obese women had lower risk of microsomia (OR=0.65, 95% CI 0.48-0.88, and OR=0.47, 95% CI 0.260-0.84, respectively). On the other hand, they showed a higher risk of having gestational diabetes mellitus (OR=2.0, 95% CI 1.60-2.5 and OR=2.4, CI 95% 1.7-3.4), macrosomia (OR=1.6, 95% CI 1.3-2.0 and OR=1.5, CI 95% 1.1-2.2), and hypertensive disorders (OR=2.5, 95% CI 2.0-3.0 and OR=6.6, 95% CI 5.0-8.6), than women with normal nutritional status. Obesity was also a risk factor for pre-eclampsia (OR=3.9, 95% CI 2.4-6.4).
Brazilian national health system provides care for approximately 75% of the population4. These data show that more than1/3 of women seen in selected prenatal clinics of the national health system feel out of normal nutritional range (18.5<BMI<25.0). Of these, there were about 4 women overweight for every underweight one. Though these prevalences varied somewhat over the categories such as age, educational level, skin color, parity, and geographic region, significant overweight prevalences were present in all categories studied. These data are of a major importance given the increased risk of adverse outcomes among overweight here demonstrated.
The study findings are consistent with recent population-based surveys of nutritional status in Brazil. Monteiro et al7 reported an obesity prevalence of 13.3% in a probability sample of Brazilian women aged 25-64 years8 conducted in 1989. While not all women in these population surveys have equal probability of becoming pregnant, it is important to add to these data from clinical samples in order to obtain a more complete picture of the significance of these recent changes in nutritional status to current obstetric practice.
The study data illustrate important risks at both extremes of the nutritional status spectrum, as both under and overweight at the beginning of gestation are associated with adverse pregnancy outcomes, consistent with other authors' findings in different contexts. While underweight women presented a higher frequency of microsomia,6 overweight was related to macrosomia and other disease conditions, such as gestational diabetes mellitus and hypertensive disorders.6,12 As being overweight is commonly seen and confers risk not only to the mother but also to the neonate, the study findings, along with the literature, call for greater attention to the prevention and management of obesity in childbearing age women, both prior to and during pregnancy.
The dilemma of weight control strategies for overweight pregnant women should be stressed. Although a lesser weight gain during pregnancy might be desirable for overweight women, insufficient weight gain is associated with an increased risk of microsomia,6 per se a risk for several undesirable outcomes, both immediate and chronic.1 Thus, international limits for adequate weight gain have been set for specific nutritional categories, from lean to obese. It was previously reported here that only ¼ of the overweight women studied gained weight within these recommended limits.9
There are some limitations in the interpretation of these results. As the study was conducted in selected clinics of the national health system of six capitals, representativeness cannot be assured. However, comparisons of data on educational level, nutritional status and gestational age at delivery5 suggest that the study sample characteristics are comparable with those of pregnant women living in large metropolitan areas of Brazil. In this regard, the data are also less likely to be representative of those women seen outside of the national health system. An additional limitation is that prepregnancy weight was reported and not objectively measured, and thus subject to recall bias. However, based on previous findings concerning weight recall for Brazilian women studied outside of pregnancy10 and other studies about referred weight,2 it seems that weight measure bias is probably small.
As a conclusions, overweight nutritional status is highly prevalent among women seen in prenatal public clinics of major Brazilian cities, even for the age range of 20¾24 years. Approximately 25% of women are overweight at conception. Older black multiparous women with lower educational level and living in the southern or southeastern regions are more likely to be overweight at the onset of pregnancy. Maternal overweight status is associated with adverse pregnancy outcomes. Greater awareness of these facts are key for minimizing the risks of obesity for pregnant women and their offspring.
To the following people for the study regional coordination in the centers: AJ Reichelt of Santa Casa de Misericórdia and Hospital de Clínicas de Porto Alegre; JMD Pousada of Instituto de Perinatologia da Bahia (IPERBA); T Yamashita of Hospital do Servidor Público Estadual "Francisco Morato de Oliveira", São Paulo); ERS Spichler of Instituto Fernandes Figueira. Fundação Oswaldo Cruz, Rio de Janeiro; MM Teixeira of Serviço de Obstetrícia do Posto de Assistência Médica da Cadajás, Manaus; A Costa e Forti of Maternidade Escola Assis Chateaubriand da Universidade do Ceará, Fortaleza.
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Luciana Bertoldi Nucci
Rua da Granja Julieta, 9/34
04721-060 São Paulo, SP, Brasil
Partial supported by "Ministério da Saúde"; "Programa de Apoio a Núcleos de Excelência" (PRONEX, Process nº 661041/1998-4); "Conselho Nacional de Desenvolvimento Científico e Tecnológico" (CNPq, Process nº 520368/95-9); "Fundação de Apoio à Pesquisa do Rio Grande do Sul" (FAPERGS); ; Organização Pan-Americana da Saúde (OPAS); Fundo de Incentivo à Pesquisa (FIPE, Process nº 97217 do Hospital de Clínicas de Porto Alegre, and Bristol-Myers Squibb Foundation.
Submitted on 5/4/2001. Reviewed on 29/8/2001. Approved on 27/9/2001.