The Influence Of Breastfeeding On Postpartum Weight Retention
Transcript Of The Influence Of Breastfeeding On Postpartum Weight Retention
Yale University
EliScholar – A Digital Platform for Scholarly Publishing at Yale
Public Health Theses
School of Public Health
January 2012
The Influence Of Breastfeeding On Postpartum Weight Retention
Mariam Girguis
Yale University, [email protected]
Follow this and additional works at: http://elischolar.library.yale.edu/ysphtdl
Recommended Citation
Girguis, Mariam, "The Influence Of Breastfeeding On Postpartum Weight Retention" (2012). Public Health Theses. 1107. http://elischolar.library.yale.edu/ysphtdl/1107
This Open Access Thesis is brought to you for free and open access by the School of Public Health at EliScholar – A Digital Platform for Scholarly Publishing at Yale. It has been accepted for inclusion in Public Health Theses by an authorized administrator of EliScholar – A Digital Platform for Scholarly Publishing at Yale. For more information, please contact [email protected]
THE INFLUENCE OF BREASTFEEDING ON POSTPARTUM WEIGHT RETENTION By
Mariam S. Girguis
A Thesis Presented to The Department of Chronic Disease Epidemiology
Yale University In Candidacy for the Degree of
Master of Public Health
1
Permission for photocopying, microfilming, or computer electronic scanning of “The Role of Breastfeeding on Postpartum Weight Retention” for the purpose of individual scholarly consultation or reference is hereby granted by the author. This permission is not to be interpreted as affecting publication of this work or otherwise placing it in the public domain, and the author reserves all rights of ownership guaranteed under common law protection of unpublished manuscripts.
__________________________________________ Signature of Author
__________________________________________ Date
2
Abstract
Background: Weight gained during pregnancy and not lost postpartum has been identified as a contributor to increased obesity risk among women of childbearing age.
Objective: To determine the influence of “any” and exclusive breastfeeding duration on postpartum weight retention (PPWR).
Design: Women were selected from the longitudinal Infant Feeding Practices Study II (IFPS II) . All women who reported both their pre-pregnancy weight and at least one postpartum weight were included in the analyses. Multivariate logistic and linear regression models were used to examine the association between “any” and exclusive breastfeeding duration and PPWR at 3 (n=2254), 6 (n=1966), 9 (n= 1824), and 12 (n=1693) months postpartum. Models were controlled for pre-pregnancy BMI, maternal age, parity, poverty level, education, and prenatal smoking status.
Results: Results indicate that breastfeeding is associated with PPWR. “Any” breastfeeding for between 3-4 and 4-5 months was associated with an increased odds of retaining above median PPWR at 12 months postpartum (OR: 1.99, 95%, CI: 1.21, 3.24; OR: 1.83, 95% CI; 1.01-3.29). By contrast, exclusive breastfeeding was associated with decreased odds of retaining above median PPWR at 6 months (OR: 0.63, 95% CI: 0.41-0.98). Exclusive breastfeeding for at least 6 months was also associated with significantly decreased odds of retaining above median PPWR at 6, 9, and 12 months postpartum.
Conclusion: Exclusive breastfeeding for at least 6 months was associated with decreased odds of retaining above median PPWR.
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Acknowledgments I would like to acknowledge Dr. Rafael Perez-Escamilla and Dr. Susan Mayne of Yale School of Public Health for their mentorship and support. I also would like to thank CDC for allowing me access to the IFPS II dataset.
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Table of Contents Introduction………………………………………………………………………… 7 Methods…………………...……………………………………………………….12
Participants……………………………………………….………………..12 Analysis Sample…………………………………………………………...12 Variable Measures…………………………………….…………………...14 Statistical analysis…………………………………………………………16 Results……………………………………………………………..………………18 Table 1…………………………………………………………………….18 Table 2a-d…………………………………………………………………21 Table 3…………………………………………………………………….26 Table 4a-d…………………………………………………………………29 Discussion……………………………………………..…………………………..31 Conclusion………………………………………………………………..……….35 References…………………………………………………………………..……..36 Appendix…………………………………………………………………………..40
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List of Tables TABLE 1: Characteristics (Means and Standard Deviations) of Infant Feeding Practice Study II (IFPS II) study sample.
TABLE 2a-d: Characteristics (Mean and Standard Deviations for continuous variables and N and Row Percent for categorical variables) by tertile of Postpartum Weight Retention (PPWR) at each time point in the IFPS II study sample
TABLE 3: Bivariate Associations of PPWR and Breastfeeding Duration (Mean and Standard Deviations) in the IFPS II study sample
TABLE 4a-d: Odds of retaining above median PPWR by breastfeeding duration and Intensity in the IFPS II Study cohort.
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Due to a combination of biological, hormonal, environmental, and cultural factors, obesity distinctively affects women’s health. Approximately 24.5% of women living in the United States aged 20-44 years of age are overweight (BMI 25.0-29.9 kg/m2) and 23% are obese (BMI > 30 kg/m2). Among those who are obese, 10.3% meet the criteria for class II or III obesity (BMI > 35 kg/m2)[1]. As researchers are trying to understand the multiple influences on obesity, they have concluded that reproductive transitions, such as pregnancy, increase the risk for obesity[2]. As pregnancy is likely to be a significant risk factor for excessive weight gain for most women, this study seeks to understand the influence of breastfeeding duration on postpartum weight retention (PPWR). PPWR at time t is defined as the weight gain from pregnancy which is not lost following childbirth. It is usually calculated by subtracting a mother’s prepregnant weight from her postpartum weight at time t. Postpartum Weight Retention
Several studies have concluded that excess weight gain during pregnancy and failure to lose weight after pregnancy are risk factors for long term obesity. Rooney et al (2002) found that pregnancy weight gain accounts for more than half of adult weight gain among overweight women who previously had a normal weight [3] . Pregnancy has frequently been cited as a contributor to overweight. Women experience a wide range of weight gains during pregnancy and PPWR. Although the majority of studies conclude that significant PPWR exists, they report that median PPWR ranges from -0.6 to 7.7 lbs. [4-10]. This wide range of PPWR estimates across studies may be explained by different methods used for estimating PPWR and/or sample characteristics.
One of the first reports demonstrating significant PPWR studied 7,000 women in the United States longitudinally and found that PPWR was 7.7 lbs on average [4]. In this study
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PPWR was defined as the weight retained in the time elapsed between births (from one pregnancy to the subsequent pregnancy) in relationship to maternal weight prior to the first pregnancy. Using a similar study design, Harrison et al conducted a study in the United Kingdom. After controlling for age, they found that women lost 0.6 lb. between two subsequent pregnancies. They concluded that pregnancy did not significantly affect weight gain [5]. A subsequent study, conducted by the same authors followed a group of women for 2.5 years postpartum and found a significant yet small influence of pregnancy on PPWR which was 1.1 lbs. on average [6]. Consistent with this study, a Swedish Cohort study [7] found that average PPWR, 12 months after birth, was also 1.1 lbs. Likewise, others have estimated that premenopausal and post-menopausal women gain an average of 1 lbs. per year throughout life[47].
Rookus et al [8] followed a cohort of 49 women for 9 months postpartum in the Netherlands and found that there was no significant difference in BMI between women 9 months postpartum and their age matched non-pregnant counterparts[8]. Few studies have been able to investigate the influence of pregnancy on PPWR for longer follow up periods. Two longitudinal studies following women for 10 years postpartum in the United States and Australia found that there was a significant but modest positive association between pregnancy and PPWR[9, 10].
The overall influence of pregnancy on weight gain is difficult to estimate as previous studies have used diverse samples and methods for estimating PPWR. Thus far the literature suggests that there is a significant yet small association between pregnancy and weight gain. While the majority of women may not experience significant PPWR, there may be subgroups of women who do retain substantial weight after delivery. A prospective cohort study in the United States concluded that 15-25.6% of mothers retain at least 10 lbs. postpartum [11, 12].
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Gestational weight gain (GWG) has also been associated with PPWR [12, 15, 16]. In general, the more weight that women gain during pregnancy, the more PPWR they experience [16]. Excessive gestational weight gain has been cited as the primary risk factor for retaining excessive weight in the postpartum period [10, 11, 15-18]. Women with a gestational weight gain above the recommendations of the IOM had greater PPWR in a cohort of Brazilian women [15]. The Institute of Medicine (IOM) has issued gestational weight gain guidelines as a function of pre-pregnancy BMI[13]. The most updated 2009 IOM pregnancy weight gain guidelines are similar to its 1990 guidelines, except now there is an upper limit of how much weight obese women should gain while pregnant[13]. These guidelines provide cut off points for investigating gestational weight gain and PPWR. A study conducted in the United States found that for those women who met the recommended gestational weight gain, PPWR at 10 to 18 months for White women was 1.6 lbs. while for Black women it was 7. 2 lb.[14]. Among 18–45 year old Brazilian women living in Rio de Janeiro, each unit increase in pre-pregnancy BMI was associated with a decrease of 0.51 kg in PPWR[15]. Other risk factors associated with PPWR include prepregnancy BMI, primiparity, duration of breastfeeding, smoking, high energy intake and low physical activity, although these associations have not been found in all studies[11, 17]. Smoking relapse among prenatal smokers was found to reduce PPWR compared to women who remained abstinent postpartum [19]. Breastfeeding and Postpartum Weight Retention
The relationship between breastfeeding and PPWR remains elusive. A systematic review of 15 observational studies concluded that there may exist a dose-response relationship between breastfeeding duration/intensity and PPWR, and that weight loss differences attributed to breastfeeding were transient, being more evident within 3 to 6 months postpartum[20]. Another systematic review based on similar evidence concluded that the influence of breastfeeding on
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EliScholar – A Digital Platform for Scholarly Publishing at Yale
Public Health Theses
School of Public Health
January 2012
The Influence Of Breastfeeding On Postpartum Weight Retention
Mariam Girguis
Yale University, [email protected]
Follow this and additional works at: http://elischolar.library.yale.edu/ysphtdl
Recommended Citation
Girguis, Mariam, "The Influence Of Breastfeeding On Postpartum Weight Retention" (2012). Public Health Theses. 1107. http://elischolar.library.yale.edu/ysphtdl/1107
This Open Access Thesis is brought to you for free and open access by the School of Public Health at EliScholar – A Digital Platform for Scholarly Publishing at Yale. It has been accepted for inclusion in Public Health Theses by an authorized administrator of EliScholar – A Digital Platform for Scholarly Publishing at Yale. For more information, please contact [email protected]
THE INFLUENCE OF BREASTFEEDING ON POSTPARTUM WEIGHT RETENTION By
Mariam S. Girguis
A Thesis Presented to The Department of Chronic Disease Epidemiology
Yale University In Candidacy for the Degree of
Master of Public Health
1
Permission for photocopying, microfilming, or computer electronic scanning of “The Role of Breastfeeding on Postpartum Weight Retention” for the purpose of individual scholarly consultation or reference is hereby granted by the author. This permission is not to be interpreted as affecting publication of this work or otherwise placing it in the public domain, and the author reserves all rights of ownership guaranteed under common law protection of unpublished manuscripts.
__________________________________________ Signature of Author
__________________________________________ Date
2
Abstract
Background: Weight gained during pregnancy and not lost postpartum has been identified as a contributor to increased obesity risk among women of childbearing age.
Objective: To determine the influence of “any” and exclusive breastfeeding duration on postpartum weight retention (PPWR).
Design: Women were selected from the longitudinal Infant Feeding Practices Study II (IFPS II) . All women who reported both their pre-pregnancy weight and at least one postpartum weight were included in the analyses. Multivariate logistic and linear regression models were used to examine the association between “any” and exclusive breastfeeding duration and PPWR at 3 (n=2254), 6 (n=1966), 9 (n= 1824), and 12 (n=1693) months postpartum. Models were controlled for pre-pregnancy BMI, maternal age, parity, poverty level, education, and prenatal smoking status.
Results: Results indicate that breastfeeding is associated with PPWR. “Any” breastfeeding for between 3-4 and 4-5 months was associated with an increased odds of retaining above median PPWR at 12 months postpartum (OR: 1.99, 95%, CI: 1.21, 3.24; OR: 1.83, 95% CI; 1.01-3.29). By contrast, exclusive breastfeeding was associated with decreased odds of retaining above median PPWR at 6 months (OR: 0.63, 95% CI: 0.41-0.98). Exclusive breastfeeding for at least 6 months was also associated with significantly decreased odds of retaining above median PPWR at 6, 9, and 12 months postpartum.
Conclusion: Exclusive breastfeeding for at least 6 months was associated with decreased odds of retaining above median PPWR.
3
Acknowledgments I would like to acknowledge Dr. Rafael Perez-Escamilla and Dr. Susan Mayne of Yale School of Public Health for their mentorship and support. I also would like to thank CDC for allowing me access to the IFPS II dataset.
4
Table of Contents Introduction………………………………………………………………………… 7 Methods…………………...……………………………………………………….12
Participants……………………………………………….………………..12 Analysis Sample…………………………………………………………...12 Variable Measures…………………………………….…………………...14 Statistical analysis…………………………………………………………16 Results……………………………………………………………..………………18 Table 1…………………………………………………………………….18 Table 2a-d…………………………………………………………………21 Table 3…………………………………………………………………….26 Table 4a-d…………………………………………………………………29 Discussion……………………………………………..…………………………..31 Conclusion………………………………………………………………..……….35 References…………………………………………………………………..……..36 Appendix…………………………………………………………………………..40
5
List of Tables TABLE 1: Characteristics (Means and Standard Deviations) of Infant Feeding Practice Study II (IFPS II) study sample.
TABLE 2a-d: Characteristics (Mean and Standard Deviations for continuous variables and N and Row Percent for categorical variables) by tertile of Postpartum Weight Retention (PPWR) at each time point in the IFPS II study sample
TABLE 3: Bivariate Associations of PPWR and Breastfeeding Duration (Mean and Standard Deviations) in the IFPS II study sample
TABLE 4a-d: Odds of retaining above median PPWR by breastfeeding duration and Intensity in the IFPS II Study cohort.
6
Due to a combination of biological, hormonal, environmental, and cultural factors, obesity distinctively affects women’s health. Approximately 24.5% of women living in the United States aged 20-44 years of age are overweight (BMI 25.0-29.9 kg/m2) and 23% are obese (BMI > 30 kg/m2). Among those who are obese, 10.3% meet the criteria for class II or III obesity (BMI > 35 kg/m2)[1]. As researchers are trying to understand the multiple influences on obesity, they have concluded that reproductive transitions, such as pregnancy, increase the risk for obesity[2]. As pregnancy is likely to be a significant risk factor for excessive weight gain for most women, this study seeks to understand the influence of breastfeeding duration on postpartum weight retention (PPWR). PPWR at time t is defined as the weight gain from pregnancy which is not lost following childbirth. It is usually calculated by subtracting a mother’s prepregnant weight from her postpartum weight at time t. Postpartum Weight Retention
Several studies have concluded that excess weight gain during pregnancy and failure to lose weight after pregnancy are risk factors for long term obesity. Rooney et al (2002) found that pregnancy weight gain accounts for more than half of adult weight gain among overweight women who previously had a normal weight [3] . Pregnancy has frequently been cited as a contributor to overweight. Women experience a wide range of weight gains during pregnancy and PPWR. Although the majority of studies conclude that significant PPWR exists, they report that median PPWR ranges from -0.6 to 7.7 lbs. [4-10]. This wide range of PPWR estimates across studies may be explained by different methods used for estimating PPWR and/or sample characteristics.
One of the first reports demonstrating significant PPWR studied 7,000 women in the United States longitudinally and found that PPWR was 7.7 lbs on average [4]. In this study
7
PPWR was defined as the weight retained in the time elapsed between births (from one pregnancy to the subsequent pregnancy) in relationship to maternal weight prior to the first pregnancy. Using a similar study design, Harrison et al conducted a study in the United Kingdom. After controlling for age, they found that women lost 0.6 lb. between two subsequent pregnancies. They concluded that pregnancy did not significantly affect weight gain [5]. A subsequent study, conducted by the same authors followed a group of women for 2.5 years postpartum and found a significant yet small influence of pregnancy on PPWR which was 1.1 lbs. on average [6]. Consistent with this study, a Swedish Cohort study [7] found that average PPWR, 12 months after birth, was also 1.1 lbs. Likewise, others have estimated that premenopausal and post-menopausal women gain an average of 1 lbs. per year throughout life[47].
Rookus et al [8] followed a cohort of 49 women for 9 months postpartum in the Netherlands and found that there was no significant difference in BMI between women 9 months postpartum and their age matched non-pregnant counterparts[8]. Few studies have been able to investigate the influence of pregnancy on PPWR for longer follow up periods. Two longitudinal studies following women for 10 years postpartum in the United States and Australia found that there was a significant but modest positive association between pregnancy and PPWR[9, 10].
The overall influence of pregnancy on weight gain is difficult to estimate as previous studies have used diverse samples and methods for estimating PPWR. Thus far the literature suggests that there is a significant yet small association between pregnancy and weight gain. While the majority of women may not experience significant PPWR, there may be subgroups of women who do retain substantial weight after delivery. A prospective cohort study in the United States concluded that 15-25.6% of mothers retain at least 10 lbs. postpartum [11, 12].
8
Gestational weight gain (GWG) has also been associated with PPWR [12, 15, 16]. In general, the more weight that women gain during pregnancy, the more PPWR they experience [16]. Excessive gestational weight gain has been cited as the primary risk factor for retaining excessive weight in the postpartum period [10, 11, 15-18]. Women with a gestational weight gain above the recommendations of the IOM had greater PPWR in a cohort of Brazilian women [15]. The Institute of Medicine (IOM) has issued gestational weight gain guidelines as a function of pre-pregnancy BMI[13]. The most updated 2009 IOM pregnancy weight gain guidelines are similar to its 1990 guidelines, except now there is an upper limit of how much weight obese women should gain while pregnant[13]. These guidelines provide cut off points for investigating gestational weight gain and PPWR. A study conducted in the United States found that for those women who met the recommended gestational weight gain, PPWR at 10 to 18 months for White women was 1.6 lbs. while for Black women it was 7. 2 lb.[14]. Among 18–45 year old Brazilian women living in Rio de Janeiro, each unit increase in pre-pregnancy BMI was associated with a decrease of 0.51 kg in PPWR[15]. Other risk factors associated with PPWR include prepregnancy BMI, primiparity, duration of breastfeeding, smoking, high energy intake and low physical activity, although these associations have not been found in all studies[11, 17]. Smoking relapse among prenatal smokers was found to reduce PPWR compared to women who remained abstinent postpartum [19]. Breastfeeding and Postpartum Weight Retention
The relationship between breastfeeding and PPWR remains elusive. A systematic review of 15 observational studies concluded that there may exist a dose-response relationship between breastfeeding duration/intensity and PPWR, and that weight loss differences attributed to breastfeeding were transient, being more evident within 3 to 6 months postpartum[20]. Another systematic review based on similar evidence concluded that the influence of breastfeeding on
9