Nutritional status of pregnant women : prevalence and associated pregnancy outcomes Estado nutricional de gestantes : prevalência e desfechos associados à gravidez

Correspondence to: Luciana Bertoldi Nucci Rua da Granja Julieta, 9/34 04721-060 São Paulo, SP, Brasil E-mail: lbnucci@terra.com.br 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.


Introduction
Although obesity is well recognized as a current public health problem, its prevalence and impact among pregnant women have been less investigated in Brazil.The objective of the study was to evaluate the impact of pre-obesity and obesity among pregnant women, describing its prevalence and risk factors, and their association with adverse pregnancy outcomes.Methods A cohort of 5,564 pregnant women, aged 20 years or more, enrolled at aproximately 20 to 28 weeks of pregnancy, seen in prenatal public clinics of six state capitals in Brazil were followed up, between 1991 and 1995.Prepregnancy weight, age, educational level and parity were obtained from a standard questionnaire.Height was measured in duplicate and the interviewer assigned the skin color.Nutritional status was defined using body mass index (BMI), according to World Health Organization (WHO) criteria.Odds ratios and 95% confidence interval were calculated using logistic regression.

Conclusions
Overweight nutritional status (obesity and pre-obesity) was seen in 25% of adult pregnant women and it was associated with increased risk for several adverse pregnancy outcomes, such as gestational diabetes and pre-eclampsia.

INTRODUCTION
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. 13Maternal nutritional status is an important determinant of pregnancy outcomes since prepregnancy underweight has been traditionally considered a risk factor for adverse gestation outcomes. 3Obesity also increases pregnancy complications, such as gestational diabetes, hypertensive disorders, and perinatal morbimortality. 12azil is a heterogeneous country regarding its population characteristics, and health problems of preobesity and obesity coexist with undernutrition.Recent trend analyses of nutritional status have placed the problem of obesity squarely on the Brazilian public health agenda. 8e 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.

METHODS
The study was conducted in prenatal care clinics of the national health system (Sistema Único de Saúde -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.Ana-lysis 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/m 2 ), normoweight (18.5 kg/ m 2 ≤ BMI <25 kg/m 2 ), pre-obesity (25 kg/m 2 ≤ BMI< 30 kg/m 2 ), and obesity (BMI≥30 kg/m 2 ).Women who fall in the latter two categories were also characterized as overweight. 13stational 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. 14Gestational 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 90 th percentile for the gestational age of the study sample; microsomia was defined as birth weight below the 10 th percentile for the gestational age.Hypertensive disor- Frequencies of underweight, pre-obesity and obesity -and their 95% confidence intervals -, both crude and adjusted, are displayed, the latter obtained through logistic regression. 11,15Odds 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.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%-20.3%),and obesity 5.5% (4.9%-6.2%): underweight (BMI<18.5 kg/m 2 ), pre-obesity (25.0 kg/m 2 ≤BMI<30 kg/m 2 ) and obesity (BMI≥30.0kg/m 2 ); reference group is those with normal BMI (18.5 kg/m 2 ≤BMI<25 kg/m 2 ).GDM -Gestational diabetes mellitus 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).

DISCUSSION
Brazilian national health system provides care for approximately 75% of the population 4 .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, sig-nificant 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 al 7 reported an obesity prevalence of 13.3% in a probability sample of Brazilian women aged 25-64 years 8 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. 6,12As 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. 9ere 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 delivery 5 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 pregnancy 10 and other studies about referred weight, 2 it seems that weight measure bias is probably small.As a conclusion, overweight nutritional status is highly prevalent among women seen in prenatal public clinics of major Brazilian cities, even for the age range of 20-24 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.
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.
www.fsp.usp.br/rspNutritional status of pregnant women Nucci LB et al. ders

Table 2 -
Frequency (95%CI) of prepregnancy World Health Organization nutritional status* categories among 5,314 women aged 20 to 48, 1990 to 1994.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.

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 Table1 -Characteristics of studied and excluded pregnant women aged 20 to48, 1990 to 1994.

Table 3 -
Age adjusted* prevalence (95%CI) of prepregnancy World Health Organization nutritional status** among 5,314 women aged 20 to 48, by study center, years of education, skin color and parity, 1990 to 1994.
*BMI cut points according to WHO