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DOI: 10.1111/mcn.12149
Original Article
Weight-related self-efficacy in relation to maternal body weight from early pregnancy to 2 years post-partum Leah M. Lipsky*, Myla S. Strawderman† and Christine M. Olson† *Health Behavior Branch, Division of Intramural Public Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA, and †Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA
Abstract Excessive gestational weight gain may lead to long-term increases in maternal body weight and associated health risks. The purpose of this study was to examine the relationship between maternal body weight and weightrelated self-efficacy from early pregnancy to 2 years post-partum. Women with live, singleton term infants from a population-based cohort study were included (n = 595). Healthy eating self-efficacy and weight control selfefficacy were assessed prenatally and at 1 year and 2 years post-partum. Body weight was measured at early pregnancy, before delivery, and 6 weeks, 1 year and 2 years post-partum. Behavioural (smoking, breastfeeding) and sociodemographic (age, education, marital status, income) covariates were assessed by medical record review and baseline questionnaires. Multi-level linear regression models were used to examine the longitudinal associations of self-efficacy measures with body weight. Approximately half of the sample (57%) returned to early pregnancy weight at some point by 2 years post-partum, and 9% became overweight or obese at 2 years post-partum. Body weight over time was inversely related to healthy eating (β = −0.57, P = 0.02) and weight control (β = −0.99, P < 0.001) self-efficacy in the model controlling for both self-efficacy measures as well as time and behavioural and sociodemographic covariates. Weight-related self-efficacy may be an important target for interventions to reduce excessive gestational weight gain and post-partum weight gain. Keywords: maternal weight change, weight-related behaviours, behaviour-specific self-efficacy, prospective cohort. Correspondence: Dr Leah M Lipsky, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Division of Intramural Public Health Research, 6100 Executive Blvd, Suite 7B13, Bethesda, MD 20852, USA. E-mail: [email protected]
Introduction Excessive pregnancy-related weight gain may lead to long-term increases in maternal body weight (Ohlin & Rössner 1990; Williamson et al. 1994; Boardley et al. 1995; Linné et al. 2002; Amorim et al. 2007) and is a risk factor for obesity among women of reproductive age (Rooney & Schauberger 2002; Crerand et al. 2006). While the mean reported retention of pregnancy-related weight gain at 1 year post-partum is essentially zero (Schmitt et al. 2007), research has
consistently shown substantial retention of more than approximately 5 kg in a sizable minority (12–25%) of mothers (Ohlin & Rössner 1990; Olson & Strawderman 2003; Olson et al. 2003; Herring et al. 2008; Gunderson 2009). The initiation of weight gain in the post-partum period has also been reported 6–12 months after parturition (McKeown & Record 1957; Janney et al. 1997; Maddah & Nikooyeh 2009; Onyango et al. 2011; Lipsky et al. 2012). This amount of weight gain may prove difficult to reverse, increasing risk of complications in subsequent pregnancies
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
1
2
L.M. Lipsky et al.
(Villamor & Cnattingius 2006). Further, some evidence indicates an association of gestational weight gain with preferential accumulation of visceral fat, which is related to increased cardiometabolic risk (Gunderson et al. 2004). Maternal weight change and weight-related behaviours during pregnancy and the post-partum period are influenced by psychosocial aspects of pregnancy, new motherhood and child rearing. Harris et al. (1999) demonstrated a trend towards a positive relationship of social support (as assessed by larger social networks) with decreased long-term maternal weight gain, and a significant relationship between decreased body satisfaction and increased maternal weight at approximately two and a half years post-partum (Harris et al. 1999). Mothers describing efforts to lose pregnancy-associated weight gain have described challenges associated with social support, time resources, motivation and changing body perception (Thornton et al. 2006; Groth & David 2008; Montgomery et al. 2011). Weight-related self-efficacy may be an important influence on maternal weight development. Selfefficacy refers to an individual’s perceived ability to perform a behaviour to produce a desired outcome in spite of potential barriers (Bandura 1977). Increased self-efficacy is hypothesised to influence the amount of effort an individual is willing to expend to achieve a specific behaviour and the persistence with which the individual engages in the behaviour. Thus, increased self-efficacy is hypothesised to increase the likelihood of engaging in specific behaviours and to influence associated health outcomes. Previous research has revealed significant associations between exercise self-efficacy and healthy eating selfefficacy at 1 year post-partum with concurrent exercise frequency and change in food intake at 6–12 months post-partum (Langenberg et al. 2000; Hinton
& Olson 2001a; Hinton & Olson 2001b). Maternal weight-related self-efficacy has also been positively related to previous success with weight loss and exercise frequency prior to pregnancy as well as prenatal fruit and vegetable intake (Kendall et al. 2001). Few studies have examined the relationship between weight-related self-efficacy and maternal body weight. Although one study supports the hypothesised relationships between weight-related self-efficacy and concurrent maternal body weight (Kendall et al. 2001), associations of weight-related self-efficacy with post-partum body weight have not been explored. The small number and short duration of longitudinal assessments are common limitations of studies of maternal body weight, with few previous prospective studies consistently following weight development beyond 1 year post-partum, and many studies relying on a single assessment of the explanatory and dependent variables. Use of self-reported body weight is also common, which may lead to biased estimates of the influence of self-efficacy on weight outcomes. Moreover, we are aware of no previous studies that have investigated the importance of weight-related self-efficacy beyond 1 year postpartum or assessed this construct longitudinally. Repeated assessments of maternal weight-related self-efficacy may be informative given the anticipated influence of aspects of new motherhood, infant care and changing family dynamics on perceived barriers to weight-related behaviours (Antonucci & Mikus 1988; Nuss et al. 2006; Setse et al. 2008). The purpose of this study was to examine the relationship between weight-related self-efficacy and maternal body weight from early pregnancy to 2 years post-partum. Participants were enrolled in an observational cohort study, completing repeated assessments of body weight and weight-related selfefficacy. We hypothesised that higher weight-related
Key messages • Maternal weight-related self-efficacy is significantly associated with body weight between early pregnancy and 2 years post-partum. • These measures of weight-related self-efficacy exhibit validity with respect to maternal body weight. • Maternal weight-related self-efficacy may be an important target for interventions to prevent excessive gestational weight gain and post-partum weight retention.
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
Weight self-efficacy and maternal body weight
self-efficacy would be related to lower maternal body weight throughout the prenatal and post-partum periods.
Materials and methods Participants Participants were recruited from among adult women over 18 years seeking prenatal care from a hospital and primary care clinic system serving 10 counties in upstate New York between March 1995 and December 1996. Eligibility criteria included no medical conditions affecting body weight, planning to keep the baby, intention to deliver within the Bassett health care system, and entering prenatal care prior to 28 weeks gestation. Additional details of study recruitment are described elsewhere (Kendall et al. 2001). The original cohort included 622 women.Women who gave birth to live singleton term infants with last pregnancy weight measures obtained within 6 weeks before parturition were included in this analysis (n = 595). Study procedures were approved by the Institutional Review Boards of the research institution and health care system. All participants gave informed consent.
Study design Data collection Data were collected primarily through medical record review at delivery, and mailed questionnaires at midpregnancy and at 6 months, 1 year and 2 years postpartum. Body weight was measured according to study protocol by health providers at antenatal and post-partum clinic visits. Early pregnancy weight was assessed before 8 weeks gestation for a majority of the sample. Where measured first trimester weight was not available (12% of the sample), values were imputed as described elsewhere (Olson & Strawderman 2003), based on a regression model derived from the relation between measured early pregnancy weight and later measured prenatal weight in the sample of women with measurements obtained in both the first and second trimesters. Additional body weight measurements were obtained prior to
delivery, and at 6 weeks, 1 year and 2 years postpartum. Individual body weight measurements at 1 year (obtained within 9–19 months post-partum) and 2 years post-partum (obtained within 21–30 months post-partum) were excluded if women had a weightrelated illness or were taking medications affecting body weight at the time of measurement (n = 2 at 1 year, n = 19 at 2 years), and if they were more than 14 weeks pregnant or had delivered a second baby (n = 16 at 1 year, n = 63 at 2 years). Post-partum body weight measures were available for n = 454, n = 548 and n = 450 women at 6 weeks, 1 years and 2 years post-partum, respectively. Health providers measured maternal height at baseline according to study protocol. Additional details regarding data collection methods are discussed elsewhere (Kendall et al. 2001; Olson & Strawderman 2003; Olson et al. 2003).
Psychosocial factors Self-efficacy of healthy eating and weight control were assessed prenatally and at 1 year and 2 years post-partum via self-reported mailed questionnaires (Table 1). Healthy eating self-efficacy items were adapted from a measure developed previously (Hofstetter et al. 1990); a measure of weight control self-efficacy was developed by the investigators of this study from in-depth interviews (Devine et al. 2000). Responses to self-efficacy items were on a 5-point scale varying from 1 = very sure to 5 = very unsure. Item scores were reverse coded so that higher scores reflected increasing self-efficacy. Summary measures were created by taking the mean of all reported items. The measures were correlated at baseline (correlation = 0.31–0.42; Kendall et al. 2001) and at post-partum assessments (correlation = 0.21–0.68), although they have been differentially associated with behavioural outcomes (Hinton & Olson 2001a; Hinton & Olson 2001b). Therefore, the measures were evaluated as separate constructs for this analysis.
Anthropometrics Weight status categories were defined as normal weight [body mass index (BMI) < 25], overweight
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
3
4
L.M. Lipsky et al.
Table 1. Weight-related self-efficacy measures Internal reliability† Self-efficacy measures
Survey items*
Prenatal
1 year
2 years
Healthy eating
Eat balanced meals Eat foods that are good for you and avoid foods that are not Eat foods that are good for you even when family or social life takes a lot of your time Fit into your regular clothes Take off any extra weight you gain Stay/get back in shape
0.81
0.76
0.75
0.90
0.86
0.83
Weight control
*Question stem: ‘How sure are you that you can . . .’. Response options varied from 0 = very sure to 5 = very unsure; scores were reverse-coded so that higher scores reflect increasing self-efficacy. †Cronbach’s alpha.
(25 ≤ BMI < 30) and obese (BMI ≥ 30). Underweight women (BMI < 18.5, n = 11) were included together with normal weight women (18.5 ≤ BMI < 25) because of insufficient numbers for a separate underweight category and to avoid excluding otherwise eligible subjects. Gestational weight gain was categorised as being within, above and below the 2009 Institute of Medicine Guidelines (IOM (Institute of Medicine) & NRC (National Research Council) 2009) in order to enable comparability with current and future studies of gestational weight gain. The recommended ranges of gestational weight gain are specified according to early pregnancy BMI (12.5– 18 kg for BMI
DOI: 10.1111/mcn.12149
Original Article
Weight-related self-efficacy in relation to maternal body weight from early pregnancy to 2 years post-partum Leah M. Lipsky*, Myla S. Strawderman† and Christine M. Olson† *Health Behavior Branch, Division of Intramural Public Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, USA, and †Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA
Abstract Excessive gestational weight gain may lead to long-term increases in maternal body weight and associated health risks. The purpose of this study was to examine the relationship between maternal body weight and weightrelated self-efficacy from early pregnancy to 2 years post-partum. Women with live, singleton term infants from a population-based cohort study were included (n = 595). Healthy eating self-efficacy and weight control selfefficacy were assessed prenatally and at 1 year and 2 years post-partum. Body weight was measured at early pregnancy, before delivery, and 6 weeks, 1 year and 2 years post-partum. Behavioural (smoking, breastfeeding) and sociodemographic (age, education, marital status, income) covariates were assessed by medical record review and baseline questionnaires. Multi-level linear regression models were used to examine the longitudinal associations of self-efficacy measures with body weight. Approximately half of the sample (57%) returned to early pregnancy weight at some point by 2 years post-partum, and 9% became overweight or obese at 2 years post-partum. Body weight over time was inversely related to healthy eating (β = −0.57, P = 0.02) and weight control (β = −0.99, P < 0.001) self-efficacy in the model controlling for both self-efficacy measures as well as time and behavioural and sociodemographic covariates. Weight-related self-efficacy may be an important target for interventions to reduce excessive gestational weight gain and post-partum weight gain. Keywords: maternal weight change, weight-related behaviours, behaviour-specific self-efficacy, prospective cohort. Correspondence: Dr Leah M Lipsky, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Division of Intramural Public Health Research, 6100 Executive Blvd, Suite 7B13, Bethesda, MD 20852, USA. E-mail: [email protected]
Introduction Excessive pregnancy-related weight gain may lead to long-term increases in maternal body weight (Ohlin & Rössner 1990; Williamson et al. 1994; Boardley et al. 1995; Linné et al. 2002; Amorim et al. 2007) and is a risk factor for obesity among women of reproductive age (Rooney & Schauberger 2002; Crerand et al. 2006). While the mean reported retention of pregnancy-related weight gain at 1 year post-partum is essentially zero (Schmitt et al. 2007), research has
consistently shown substantial retention of more than approximately 5 kg in a sizable minority (12–25%) of mothers (Ohlin & Rössner 1990; Olson & Strawderman 2003; Olson et al. 2003; Herring et al. 2008; Gunderson 2009). The initiation of weight gain in the post-partum period has also been reported 6–12 months after parturition (McKeown & Record 1957; Janney et al. 1997; Maddah & Nikooyeh 2009; Onyango et al. 2011; Lipsky et al. 2012). This amount of weight gain may prove difficult to reverse, increasing risk of complications in subsequent pregnancies
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
1
2
L.M. Lipsky et al.
(Villamor & Cnattingius 2006). Further, some evidence indicates an association of gestational weight gain with preferential accumulation of visceral fat, which is related to increased cardiometabolic risk (Gunderson et al. 2004). Maternal weight change and weight-related behaviours during pregnancy and the post-partum period are influenced by psychosocial aspects of pregnancy, new motherhood and child rearing. Harris et al. (1999) demonstrated a trend towards a positive relationship of social support (as assessed by larger social networks) with decreased long-term maternal weight gain, and a significant relationship between decreased body satisfaction and increased maternal weight at approximately two and a half years post-partum (Harris et al. 1999). Mothers describing efforts to lose pregnancy-associated weight gain have described challenges associated with social support, time resources, motivation and changing body perception (Thornton et al. 2006; Groth & David 2008; Montgomery et al. 2011). Weight-related self-efficacy may be an important influence on maternal weight development. Selfefficacy refers to an individual’s perceived ability to perform a behaviour to produce a desired outcome in spite of potential barriers (Bandura 1977). Increased self-efficacy is hypothesised to influence the amount of effort an individual is willing to expend to achieve a specific behaviour and the persistence with which the individual engages in the behaviour. Thus, increased self-efficacy is hypothesised to increase the likelihood of engaging in specific behaviours and to influence associated health outcomes. Previous research has revealed significant associations between exercise self-efficacy and healthy eating selfefficacy at 1 year post-partum with concurrent exercise frequency and change in food intake at 6–12 months post-partum (Langenberg et al. 2000; Hinton
& Olson 2001a; Hinton & Olson 2001b). Maternal weight-related self-efficacy has also been positively related to previous success with weight loss and exercise frequency prior to pregnancy as well as prenatal fruit and vegetable intake (Kendall et al. 2001). Few studies have examined the relationship between weight-related self-efficacy and maternal body weight. Although one study supports the hypothesised relationships between weight-related self-efficacy and concurrent maternal body weight (Kendall et al. 2001), associations of weight-related self-efficacy with post-partum body weight have not been explored. The small number and short duration of longitudinal assessments are common limitations of studies of maternal body weight, with few previous prospective studies consistently following weight development beyond 1 year post-partum, and many studies relying on a single assessment of the explanatory and dependent variables. Use of self-reported body weight is also common, which may lead to biased estimates of the influence of self-efficacy on weight outcomes. Moreover, we are aware of no previous studies that have investigated the importance of weight-related self-efficacy beyond 1 year postpartum or assessed this construct longitudinally. Repeated assessments of maternal weight-related self-efficacy may be informative given the anticipated influence of aspects of new motherhood, infant care and changing family dynamics on perceived barriers to weight-related behaviours (Antonucci & Mikus 1988; Nuss et al. 2006; Setse et al. 2008). The purpose of this study was to examine the relationship between weight-related self-efficacy and maternal body weight from early pregnancy to 2 years post-partum. Participants were enrolled in an observational cohort study, completing repeated assessments of body weight and weight-related selfefficacy. We hypothesised that higher weight-related
Key messages • Maternal weight-related self-efficacy is significantly associated with body weight between early pregnancy and 2 years post-partum. • These measures of weight-related self-efficacy exhibit validity with respect to maternal body weight. • Maternal weight-related self-efficacy may be an important target for interventions to prevent excessive gestational weight gain and post-partum weight retention.
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
Weight self-efficacy and maternal body weight
self-efficacy would be related to lower maternal body weight throughout the prenatal and post-partum periods.
Materials and methods Participants Participants were recruited from among adult women over 18 years seeking prenatal care from a hospital and primary care clinic system serving 10 counties in upstate New York between March 1995 and December 1996. Eligibility criteria included no medical conditions affecting body weight, planning to keep the baby, intention to deliver within the Bassett health care system, and entering prenatal care prior to 28 weeks gestation. Additional details of study recruitment are described elsewhere (Kendall et al. 2001). The original cohort included 622 women.Women who gave birth to live singleton term infants with last pregnancy weight measures obtained within 6 weeks before parturition were included in this analysis (n = 595). Study procedures were approved by the Institutional Review Boards of the research institution and health care system. All participants gave informed consent.
Study design Data collection Data were collected primarily through medical record review at delivery, and mailed questionnaires at midpregnancy and at 6 months, 1 year and 2 years postpartum. Body weight was measured according to study protocol by health providers at antenatal and post-partum clinic visits. Early pregnancy weight was assessed before 8 weeks gestation for a majority of the sample. Where measured first trimester weight was not available (12% of the sample), values were imputed as described elsewhere (Olson & Strawderman 2003), based on a regression model derived from the relation between measured early pregnancy weight and later measured prenatal weight in the sample of women with measurements obtained in both the first and second trimesters. Additional body weight measurements were obtained prior to
delivery, and at 6 weeks, 1 year and 2 years postpartum. Individual body weight measurements at 1 year (obtained within 9–19 months post-partum) and 2 years post-partum (obtained within 21–30 months post-partum) were excluded if women had a weightrelated illness or were taking medications affecting body weight at the time of measurement (n = 2 at 1 year, n = 19 at 2 years), and if they were more than 14 weeks pregnant or had delivered a second baby (n = 16 at 1 year, n = 63 at 2 years). Post-partum body weight measures were available for n = 454, n = 548 and n = 450 women at 6 weeks, 1 years and 2 years post-partum, respectively. Health providers measured maternal height at baseline according to study protocol. Additional details regarding data collection methods are discussed elsewhere (Kendall et al. 2001; Olson & Strawderman 2003; Olson et al. 2003).
Psychosocial factors Self-efficacy of healthy eating and weight control were assessed prenatally and at 1 year and 2 years post-partum via self-reported mailed questionnaires (Table 1). Healthy eating self-efficacy items were adapted from a measure developed previously (Hofstetter et al. 1990); a measure of weight control self-efficacy was developed by the investigators of this study from in-depth interviews (Devine et al. 2000). Responses to self-efficacy items were on a 5-point scale varying from 1 = very sure to 5 = very unsure. Item scores were reverse coded so that higher scores reflected increasing self-efficacy. Summary measures were created by taking the mean of all reported items. The measures were correlated at baseline (correlation = 0.31–0.42; Kendall et al. 2001) and at post-partum assessments (correlation = 0.21–0.68), although they have been differentially associated with behavioural outcomes (Hinton & Olson 2001a; Hinton & Olson 2001b). Therefore, the measures were evaluated as separate constructs for this analysis.
Anthropometrics Weight status categories were defined as normal weight [body mass index (BMI) < 25], overweight
© 2014 John Wiley & Sons Ltd Maternal and Child Nutrition (2014), ••, pp. ••–••
3
4
L.M. Lipsky et al.
Table 1. Weight-related self-efficacy measures Internal reliability† Self-efficacy measures
Survey items*
Prenatal
1 year
2 years
Healthy eating
Eat balanced meals Eat foods that are good for you and avoid foods that are not Eat foods that are good for you even when family or social life takes a lot of your time Fit into your regular clothes Take off any extra weight you gain Stay/get back in shape
0.81
0.76
0.75
0.90
0.86
0.83
Weight control
*Question stem: ‘How sure are you that you can . . .’. Response options varied from 0 = very sure to 5 = very unsure; scores were reverse-coded so that higher scores reflect increasing self-efficacy. †Cronbach’s alpha.
(25 ≤ BMI < 30) and obese (BMI ≥ 30). Underweight women (BMI < 18.5, n = 11) were included together with normal weight women (18.5 ≤ BMI < 25) because of insufficient numbers for a separate underweight category and to avoid excluding otherwise eligible subjects. Gestational weight gain was categorised as being within, above and below the 2009 Institute of Medicine Guidelines (IOM (Institute of Medicine) & NRC (National Research Council) 2009) in order to enable comparability with current and future studies of gestational weight gain. The recommended ranges of gestational weight gain are specified according to early pregnancy BMI (12.5– 18 kg for BMI
