Chile is a good example in terms of the nutrition transition as seen in developing countries . As indicated above, successful private and public programs have practically eliminated undernutrition, but the situation has gone to the other extreme, obesity being the principal problem today. The 2003 National Health Survey showed that 27.3% of all women aged 17-44 were obese, higher than the prevalence observed in men (19.2%). Figure 20.4 compares the prevalence of obesity related to age in Chilean women obtained by Berrios et al. [14-16] from observations in 1987 and 1992 in Santiago, and from the CARMEN Study in 1998 carried out in Valparaiso , using a body mass index (BMI) of 27.3 kg/m2 as a cutoff point. A marked increase in obesity prevalence was seen in the 25- to 34-year-old group, and prevalence consistently increased with age. A recent national survey showed that of women 17 years of age and older, 33% were overweight, and 25% were obese. In other words, less than 50% of the females of childbearing age have a BMI considered healthy. It is also important to point out that 2.3% of the women in this age group were morbidly obese, a characteristic not observed previously .
The increment in obesity prevalence in women is now global. For instance, in the United States, the prevalence of obesity almost doubled in a period of 20 years, from 12.7% in men and 17% in women in 1980, to 27.7 and 34% in men and women, respectively, in the year 2000 .
The high prevalence of female obesity is also seen in developing countries in other regions. An interesting study was done by Mendez et al. in which the authors analyzed data from demographic and health surveys (DHS; www.measuredhs.com) on underweight
E Berrios 86-87 m Berrios 92 ■ CARMEN 98
Fig. 20.4. Prevalence of obesity (BMI > 27.3 kg/m2) in Chilean women, 1986-1998 [14-16]
E Berrios 86-87 m Berrios 92 ■ CARMEN 98
Fig. 20.4. Prevalence of obesity (BMI > 27.3 kg/m2) in Chilean women, 1986-1998 [14-16]
(BMI <18.5 kg/m2) and overweight (BMI > 25 kg/m2) in woman from 20 to 49 years of age from developing countries in Asia, Africa, the Middle East, and Latin America . The study showed an inverse relationship between the prevalence of overweight and underweight and a direct correlation between overweight and degree of urbanization. Data were collected from 36 developing countries, and in most (32/36), overweight was more prevalent than underweight in urban areas, while in 53% (19/36) underweight was more prevalent in rural areas compared to urban settings. In all areas, prevalence of overweight was significantly correlated with gross national income per capita (GNI) .
In the United States, the incidence of obesity during pregnancy ranges from 18.5 to 38.2%, depending on the population studied and the cutoff points used to define obesity. Overweight and obesity before pregnancy are considered risk factors for specific pregnancy complications .
The increase in the prevalence of obesity has been universal in Latin America without distinction of gender, race, or age, but the situation for women is more complex. Obesity in women of childbearing age translates into heavier newborns at the end of their pregnancy, and these infants have an increased chance of being obese as both children and adults, perpetuating the cycle.
When obesity is present during pregnancy, it presents serious consequences for both the mother and the fetus. During this period, a series of metabolic changes take place in order to supply the fetus with all needed nutrients, and actually, in itself, pregnancy is a diabetogenic condition for the mother, as discussed below. Pregnant women have a higher risk for developing gestational diabetes mellitus (GDM) and hypertension, which can impair fetal development. These complications, in addition to problems at the time of delivery, could be fatal [20-26].
22.214.171.124.1 Gestational Diabetes Mellitus. The risk of developing GDM increases in direct relationship to BMI; that is, the higher the BMI the higher the risk. In the case of women with normal prepregnancy weight, the risk resides in weight gain during pregnancy; in this case, the higher the weight gain the higher the risk. This situation is not seen in overweight or obese women, since the weight gain is usually very controlled during pregnancy, their prepregnancy weight being the factor that contributes to GDM [24-26]. Thus, the presence of overweight or obesity before conception is extremely important, and it contributes more to the development of GDM than does the weight gained during pregnancy. This is mainly due to the presence of insulin resistance, which becomes more severe as the diabetogenic factors of pregnancy appear. Another risk factor for those that have gained too much weight during pregnancy is that it increases the chances of developing GDM in later pregnancies [24, 26].
Incidence of GDM is directly related to the risk for type 2 diabetes mellitus (DM2) later in life. Approximately 40% of the women who develop GDM will show glucose intolerance or DM2 later in life [21, 27-29], in addition to an increase in the cardiovascular (CV) risk, which is even higher when complicated with other factors like obesity [30, 31]. Our study of the incidence of GDM in Chilean women showed an incidence of 12% detected in the second trimester and 7% detected in the third trimester (unpublished data). Of the women that developed GDM, 70% of them were overweight or obese at the initiation of the study and showed a high prevalence of overweight and obesity in the pregestational stage, again confirming that prepregnancy weight is of paramount importance in the development of GDM.
Atalah and Castro, in a prospective study in 883 pregnant Chilean women showed that pregestational obesity (BMI > 30 kg/m2 or initial body fat mass > 30%) increased the risk for developing GDM six times (OR 6.4, 95% CI 2.1-19.6), and it increased the risk of developing hypertension eight times (OR: 7.8, 95% CI 3-20.4) .
There has been relatively little research regarding physical activity before or during pregnancy. Results from the Nurses Health Study of Harvard showed that prepregnancy physical activity, including vigorous exercise and brisk walking, conferred a protection against the development of GDM . In this prospective study, those women who spent 20 h/week or more watching television and who did not perform vigorous activity had a significantly higher risk of GDM than did women who spent less than 2 h/week watching television and were physically active (RR, 2.30; 95% CI, 1.06-4.97). The importance of physical activity in the maintenance of body weight has been studied for a long time, and there is a consensus on its importance before and during pregnancy, not only in controlling weight, but also in lowering fasting and postprandial glucose concentration .
126.96.36.199.2 Hypertension Disorders. In the United States, 5-10% of pregnant women suffer from complications of hypertension produced by their pregnancy. Although these hypertensive disorders have been known for a long time, the mechanisms involved are still unknown [34 and reviewed in Chap. 11, "Preeclampsia"]. Hypertensive disorders are classified as preeclampsia or gestational hypertension which appears during pregnancy, and preexisting hypertension or its exacerbation. The difference between preeclampsia and hypertension resides in that the latter does not show proteinuria and is more benign [34, 35]. The pathogenesis of these disorders is still unknown and could include genetic factors, immune factors, and placental abnormalities, leading to an endothelial dysfunction that is characteristic of preeclampsia . Several researchers agree that insulin resistance has an important role in the development of preeclampsia, and that this condition is directly related to obesity. An elevated pregestational BMI and an excessive weight gain during pregnancy are closely correlated to the development of preeclampsia and gestational hypertension [34, 36-38]. Although insulin resistance plays an important role in this process, we also have to consider maternal hemodynamic changes, which in obese pregnant women include elevated blood pressure, hemoconcentration, and altered cardiac function [39, 40].
In the study of Atalah and Castro cited above, the authors found that obese women had almost eight times the chance of developing hypertension (OR 7.8, 95% CI 3-20.4) when compared with normal-weight women . Similar results were obtained in Brazil .
A relatively small number of studies have investigated the changes produced by obesity at the time of birth, and even in these, there is controversy, as to the potential impact of obesity on labor and delivery, and prematurity. Garbaciak et al.  comparing pregnant women with normal weight with obese pregnant women and did not find a difference in the incidence of prematurity between groups. However, Naeye showed that obesity in the mother was a significant risk for premature births .
During the 1990s a cohort of more than 150,000 Swedish women were followed during pregnancy. Obese women had a higher risk of complications at the time of delivery than those with normal weight. The same study showed that in obese nulliparous women, there was an increase in very premature deliveries (<32 weeks of gestation), the incidence showing an increase at the extremes, i.e., in very low weight women and those with a BMI > 30 kg/m2 . Obese women also had a longer time in delivery and showed an increase in the incidence of induced deliveries compared to those women with normal weight [19, 20].
188.8.131.52.1 Cesarean Delivery. One of the main complications at the time of birth in obese woman is the increased frequency of delivery by cesarean section, showing a higher incidence than normal-weight women. This was independent of other comorbidities. Although the risk increases with a higher BMI, prepregnancy weight is even more important . Brost et al. showed in a US study of 2,929 expecting women, that each increase in one unit of pregestational BMI raised the risk of having a caesarean delivery by 7% . Similar results were obtained when BMI was determined in weeks 27-31, but in this case, the risk increased to 7.8%.
A study of 4,500 pregestational women in Brazil showed that 6.9% were obese and 43.1% were preobese. Caesarean delivery at end of pregnancy was performed in 52% of the obese and in 43% of the preobese women, with a relative risk of caesarean delivery for obese women of 1.8 (95% CI: 1.5-2). The rate of weight gain was also related to the frequency of caesarian section, the risk being 1.3 (95% CI: 1.2-1.5) for those with excess weight gain. A faster rate of weight gained also increased the risk of infection in all deliveries .
The reason for an increased incidence of caesarean delivery involves an incomplete dilation of the cervix, fetal distress, or failure of induction . The risk of caesarean delivery also increases in women with GDM and/or preeclampsia, but in the case of obese women who are without these associated pathologies, it is attributed to longer gestational periods, which produce heavier newborns.
184.108.40.206.2 Anesthesia and Postpartum. For obese women having a cesarean or a vaginal delivery, the administration of anesthesia is a delicate issue. The anatomical characteristics of obese women are different from normal-weight women. The increase in subcutaneous fat may cause anatomical abnormalities, which may make it more difficult to locate physical reference points. This has more importance in morbidly obese women since certain aspects, for instance the epidural administration, are more likely to fail. General anesthesia may also cause respiratory problems due to anatomical differences (for instance, shorter and fatter necks) .
The postpartum period is also more complicated for obese women undergoing either vaginal or cesarean delivery vis-a-vis bleeding, infection, and urinary problems. In vaginal delivery, obese women show a higher incidence of perianal rupture due to the elevated weight of the newborn . Also, they tend to stay longer in the hospital after delivery, further increasing the costs incurred .
A variety of hormonal changes occur alter delivery, and these can affect the production of breast milk. Overweight and obese women initiate lactation later than do normal-weight women due to a lower prolactin secretion in response to the infant sucking stimulation . It is reasoned, though not demonstrated, that this is caused by high progesterone levels in obese women. Normally, after delivery, progesterone levels diminish, inducing an increase in the secretion of prolactin, which stimulates milk production. Since the adipocyte is an additional source of progesterone, hormone levels would be maintained, inhibiting the activation of prolactin. Fortunately, this delay in lactation is observed initially but has no relationship with the length of the period of lactation .
220.127.116.11 Long-Term Effects of Maternal Obesity in the Mother and the Infant
The effects of obesity are not limited to immediate effects on the mother and the newborn. Other complications appear in both later in life. Those women with GDM have a higher risk of developing DM2 later in life, and if obesity is also present, they have a higher risk of developing cardiovascular disease (CVD) [30, 47]. Children of women with GDM may present with macrosomy and have a higher risk of developing DM in adolescence and CDV in adulthood. It has been proposed that this is due to an increased proportion of body fat at birth [47, 48].
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