**4. Trends of reproductive age-women's body composition**

#### **4.1 The prevalence of overweight or obese women**

Maternal size before conception plays a key role in determining pregnancy outcomes. BMI is an appropriate indicator of prepregnancy nutrition when assessed in women who are well-

According to the new guideline, underweight women (BMI<18.5 kg/m2) should gain 12.5- 18.0 kg during pregnancy, normal weight women (BMI 18.5-24.9 kg/m2) should gain 11.5- 16.0 kg, and overweight women (BMI 25.0-29.9 kg/m2) should gain 7.0-11.5 kg. This is the standard for weight gain worldwide (IOM, 2009) (Table 1). This guideline will be used in clinical practice as an effective weight management tool, and it will help to evaluate the association between these gestational weight ranges and pregnancy outcomes worldwide. Weight gain within the guidelines has been associated with healthy fetal and maternal

Total Weight Gain Rates of Weight Gains\*

Underweight 12.5-18 28-40 0.51 1 (<18.5) (0.44-0.58) (1-1.3) Normal weight 11.5-16 25-35 0.42 1 (18.5-24.9) (0.35-0.5) (0.8-1) Overweight 7-11.5 15-25 0.28 0.6 (25.0-29.9) (0.23-0.33) (0.5-0.7) Obese 5-9 11-20 0.22 0.5 (≥30.0) (0.17-0.27) (0.4-0.6)

Table 1. 2009 IOM recommendations for total and rate of weight gain during pregnancy by

In the 1990 IOM guideline, two thirds of women exceeded the recommended weight gain (Schieve et al., 1998). In a study of over 4,000 women from the University of California's San Francisco Perinatal Database, 23% of underweight women, 49% of normal-weight women, and 70% of overweight women exceeded the 1990 IOM recommendations (Carmichael et al., 1997). On the other hand, newly released, 2009 IOM recommendations were assessed by Park et al. (2011) in a population-based, retrospective cohort study of 570,672 women with singleton, full-term livebirths in Florida from 2004 to 2007. They found that 31.6% of underweight women, 42.8% of normal-weight women, and 65.0% of overweight women exceeded the 2009 IOM recommendations. These results suggest that interventions including nutritional education and behavioral strategies to promote healthy and appropriate weight gain during pregnancy should approach obese women in particular.

Maternal size before conception plays a key role in determining pregnancy outcomes. BMI is an appropriate indicator of prepregnancy nutrition when assessed in women who are well-

) Range in kg Range in lbs

\* Calculations assume a 0.5-2 kg (1.1-4.4 lbs) weight gain in the first trimester

**4. Trends of reproductive age-women's body composition** 

**4.1 The prevalence of overweight or obese women** 

Source; Reference [Institute of Medicine, 2009]

Mean (range) in Mean (range) in kg/week lbs/week

nd and 3rd Trimester

2

outcomes.

Prepregnancy BMI (kg/m<sup>2</sup>

prepregnancy BMI

nourished (Saldana et al., 2004). Overweight status and obesity have become serious global public health issues. Nearly two thirds of reproductive-aged women in the United States are currently overweight or obese (≥25 kg/m2). In the National Health and Nutrition Examination Survey (NHANES), the prevalence of obesity (BMI ≥30 kg/m2) in women aged 20-49 years continues to be high, exceeding 30% after 1999 (Flegal et al., 2010)(Fig. 2).

BMI categories (kg/m2); Underweight, <18.5; Normal, 18.5-24.9; Overweight, 25.0-29.9; Obese, ≥30.0.

Fig. 2. Trends of underweight, normal, overweight, and obese among U.S. women aged 20-40 y

In the latest NHANES data from 2007-2008 of 877 women aged 20-39 years, the prevalence of overweight status (BMI ≥25 kg/m2) and obesity were 59.5% and 34.0%, respectively. Trends are similar by age. The prevalence in all classes of obesity [(class I (30–34.9 kg/m2), class II (35–39.9 kg/m2), and class III (≥40 kg/m2) )] is lowest in white, non-Hispanic women, and highest in non-Hispanic black women in the United States (Flegal et al., 2010). Other developed countries have observed similar trends. In Australia in 2007-2008, 44.5% women aged 25-34 years and 55.3% women aged 35-44 years were overweight or obese, which constituted a marked increase over the previous 20 years (Australian Institute of Health and Welfare, 2010). In the UK, more than 50% of women in the reproductive age category of 25-44 years are overweight or obese. There has been a 69% increase in maternal obesity from 1990 to 2004, a period of only 15 years (Heslehurst et al., 2007). Thus, the increased number of overweight and obese reproductive-aged women is a worldwide phenomenon.

#### **4.2 The prevalence of underweight women**

The prevalence of underweight status (BMI<18.5 kg/m2) was only 3.1 % of reproductiveaged women in 2005-2006 (Flegal et al., 2010). Underdeveloped regions, such as South Asia or Africa, where undernutrition is generally highest, or there are socio-economic characteristics or food poverty, report the highest prevalence of underweight women (Macro International Inc, 2007). However, even some developed countries such as Japan show high prevalence rates. Over the last two decades in Japan, the prevalence of underweight women has increased from 19.6% to 21.2% in those aged 20-29 years, and from 8.6% to 13.3% in those aged 30-39 (Hayashi et al., 2006). A low body mass index in highly

The Effect of Prepregnancy Body Mass Index and Gestational Weight Gain on Birth Weight 33

A population-based retrospective cohort study was reported of 570,672 women aged 18-40 years, examining the association between the 2009 IOM recommendations and adverse infant outcomes by prepregnancy BMI reported that fifty-one percent of women were above the IOM guidelines. Gains of greater than the recommended amount were associated with increased odds of LGA (95% CI: 1.27-5.99), and gains less than those recommended were associated with decreased odds of LGA (95% CI: 0.27-0.77) (Park et al., 2011). Similar findings observed that the proportions of LGA increased with high prepregnancy BMI, but the proportions of SGA decreased. Obese women with lower weight gain or weight loss

during pregnancy had lower risk of LGA and higher risk of SGA (Nohr et al., 2008).

Many animal models have demonstrated that altering the environment in utero leads to lifelong consequences, such as high blood pressure (Mamun et al, 2009), impaired glucose tolerance (Fraser et al., 2010), insulin resistance (Ozanne & Hales, 1999), and altered hepatic architecture and function (Ozanne et al., 2001). Population-based prospective cohort studies starting from different geographical regions in the preconception period or in early fetal life and following the offspring from early fetal life until young adulthood seem to be the most suitable epidemiological design (Geelhoed & Jaddoe, 2010; Jaddoe & Witteman, 2006) (Fig. 3). There is now increasing evidence supporting the effect of the in utero environment on the development of obesity and risk factors for adult diseases (Ong, 2006; Pettitt & Jovanovic, 2007). Epidemiological studies confirm that the relationships between human birth weight and adult obesity, hypertension, or insulin resistance are U-shaped curves rather than inverse linear associations over a full range of birth weight distributions (Barker, 1998) (Fig. 4). That is, children born at both the lower - classified as SGA - and the upper – classified as LGA – ends of the birth weight spectrum are at risk of obesity and, subsequently, a range of

**6. Long-term effects of fetal environment for offspring** 

Source; Reference [Geelhoed & Jaddoe, 2010; Jaddoe & Witteman, 2006]

Fig. 3. Models for studying the fetal origins of adult diseases hypotheses in epidemiological

adult diseases in later life.

studies.

industrialized countries is not, in all probability, a result of environmental factors such as periodic food shortages and malnutrition; therefore, one must consider it an expression of constitutional low weight or a result of cosmetically induced starvation. Excessive thinness has been glamorized among reproductive aged women, and unhealthy dieting to lose weight has become a popular practice in that age group. Body image in younger women is susceptible to societal influence through mass media, such as television, movies, and magazines.
