Body Composition During Pregnancy Differs by Obesity Class

Abstract

Objective: The aim of this study is to characterize changes in body composition during pregnancy in women with obesity. Methods: Fifty-four healthy women with obesity (class 1, 30-34.9 kg/m 2 : n = 25; class 2, 35-39.9 kg/m 2 : n = 21; class 3, ≥ 40.0 kg/m 2 : n = 8) expecting a singleton pregnancy were studied. Body composition was measured in early pregnancy (13-16 weeks), midpregnancy (24-27 weeks), and late pregnancy (35-37 weeks) using air displacement plethysmography, stable isotopes, and skinfold thickness measurements. Fasting glucose, insulin, and leptin were measured. Results: The gain in fat-free mass was lower in the second trimester compared with the third (2.7 ± 0.2 to 5.3 ± 0.2 kg; P < 0.001), whereas fat mass accumulation declined over time (0.6 ± 0.3 to −0.7 ± 0.4 kg; P = 0.005). Women with class 1 and 2 obesity gained 1.1 ± 0.7 kg of fat mass during pregnancy, while women with class 3 obesity lost 4.1 ± 0.6 kg (both P < 0.001). The difference in fat accumulation between obesity classes was observed only in the second trimester (P = 0.02). Gestational weight gain was associated positively with changes in plasma concentrations of insulin, leptin, and insulin resistance (all P < 0.01). Conclusions: Gestational weight gain in pregnancy differs by obesity class and trimester. Women with class 3 obesity gain less body weight and fat mass. Fat mass gain is most likely preventable in the second trimester.Obesity (2020) 28, 268-276. Study ImportanceWhat is already known? ► Healthy gestational weight gain is inversely related to body size. ► Fat mass is the most variable component of gestational weight gain in nonobese pregnancy.What does this study add?► Weight and body composition changes during pregnancy differ by obesity class. ► Fat mass is gained during the second trimester but not the third. ► "Inadequate" weight gain is the result of fat loss.

Nutrition and Metabolic Adaptations in Physiological and Complicated Pregnancy: Focus on Obesity and Gestational Diabetes

“…Assuming a FFM accretion comparable to the other BMI classes and the inverse association between pre-gravidic BMI and FM gain throughout all BMI classes, their model suggested that maternal FM should be lost during pregnancy in cases of morbid obesity (BMI ≥ 40 kg/m 2 ) in order to optimize health outcomes (75). Body composition studies with air plethysmography confirmed that in obese women with non-excessive GWG (according to IOM), body weight was affected by changes in FM, and an inverse association between pre-gravidic BMI and FM gain was observed, with women with class 3 obesity gaining less, or loosing body weight and FM, with respect to class 1 or 2 (101).…”

“…Most et al showed that GWG in pregnancy differs by obesity classes and trimesters (101). Based on previous data of body weight and composition for pregnant women up to class 1 obesity, a linear model to predict the changes in body composition (GWG, FFM, and FM) for women with obesity class 2 and 3 and with an appropriate total GWG were elaborated.…”

“…Recently, on the basis of these studies (101,102) and of evidence on the relationship between GWG and optimal neonatal birthweight centiles (105), a revision of the recommendations on weight gain for the BMI classes of obesity has been proposed. Specifically, an increase of 2.5-7 kg in women with class 1 obesity, ≤ 4.5 kg for pregnant women with class 2 obesity, and the maintenance of pre-gravidic weight if BMI ≥ 40 Kg/m 2 (Class 3 obesity) were hypothesized.…”

The UK Pregnancies Better Eating and Activity Trial (UPBEAT); Pregnancy Outcomes and Health Behaviours by Obesity Class

“…The combined lowest risks for SGA, LGA and caesarean section have been reported in a systematic review in women with Class III obesity who gained no weight overall during pregnancy [9]. Weight maintenance in obese pregnant women is likely to be achieved by an increase in fat mobilisation, as a study of body composition revealed that women with Class III obesity lose fat, in comparison to Class I and II women who gain fat, in the second trimester [25]. However, weight gain of <5 kg in pregnancy by women with Class III obesity has been shown to significantly increase the risk of low birth weight infants and neonatal mortality, relative to those gaining weight within the NAM limits [11].…”

Analysis and Reliability of Anthropometric Measurements during Pregnancy: A Prospective Cohort Study in 208 Pregnant Women

“…However, most of these are outdated, and their validation studies do not include different kind of morphotypes (i.e., obese women), so the applicability of SFT equations to calculate body composition in women with obesity or overweight is unknown. Many studies have been recently published on this topic [13,26,30,31], although many of these do not explain a specific protocol for measuring skinfolds [2,26,30,31] or, in other cases [12,13,27], SFT is measured following older protocols (i.e., Lohman et al (1988) [32] or Taggart et al (1967) [33]). Lohman et al emphasize that the SFTs that better correlate with body density are the abdominal, triceps, and calf SFT.…”