Abstract
Purpose
Identify the prevalence and predictors of substantial postpartum weight retention (SPPWR) among WIC mothers in Southern California during their first postpartum year.
Design
Secondary data analysis.
Setting
The 2020 Los Angeles County WIC Survey.
Subjects
Mothers of children up to 1-year-old (N = 1019).
Measures
Outcome variable: SPPWR (≥5 kg above pre-pregnancy weight). Predictors: child’s age, mother’s age, race, education, employment status since having child, healthcare coverage, food insecurity, depressed mood, instrumental support, emotional support, spouse’s participation in child’s life, gestational weight gain (GWG), pre-pregnancy BMI, any breastfeeding, and gestational diabetes.
Analysis
Weighted descriptive statistics and binary logistic regression.
Results
The prevalence of SPPWR was 31%. We found that for every 1 month increase in the child’s age (proxy for postpartum duration), the likelihood of SPPWR increased by 9% (AOR = 1.09, CI = 1.04-1.15). Mothers were more likely to have SPPWR when they exceeded GWG guidelines (AOR = 3.43, CI = 2.46-4.79). Compared to mothers with normal pre-pregnancy BMIs, mothers with overweight (AOR = .64, CI = .44-.94) and obese (AOR = .39, CI = .26-.58) pre-pregnancy BMIs were less likely to experience SPPWR.
Conclusion
Postpartum duration and maternal anthropometric characteristics were associated with SPPWR during the first postpartum year. Extending WIC eligibility for postpartum mothers to 2 years through the Wise Investment in Children Act may give WIC providers the opportunity to work closely with Southern California WIC mothers to achieve a healthy weight after pregnancy.
Keywords
Purpose
Postpartum weight retention is defined as the weight gained during pregnancy that is retained after childbirth.1,2 Substantial postpartum weight retention (SPPWR) is associated with an increased risk of later obesity.2-5 Additionally, retention of excess pregnancy weight gained may contribute to maternal and neonatal complications in subsequent pregnancies.1,2,4 Consequently, the Institute of Medicine published gestational weight gain guidelines (GWG) to reduce negative outcomes for mothers and babies and identified a paucity of data on postpartum weight retention and its determinants. 2
The Special Supplemental Nutrition Program for Women, Infants, and Children (WIC) is a federal program that provides food, nutrition and breastfeeding education, and healthcare referrals to low-income mothers and children under five. 6 WIC serves half of all US infants and routinely surveys its recipents to assess its impact. 6 The WIC program’s broad reach gives its data the potential to address racial and socioeconomic disparities in SPPWR and enhance surveillance of postpartum weight.
The purpose of this study is to identify the prevalence and predictors of SPPWR among WIC mothers in Southern California during their first postpartum year using the 2020 Los Angeles County (LAC) WIC Survey. We hope our findings will inform WIC programs and policies focused on improving maternal postnatal weight outcomes.
Methods
Design
The LAC WIC Survey is a triennial telephone survey conducted in English or Spanish on a randomly selected sample of WIC families residing in LAC. 7 Participants are asked questions about one child from each family and the mother’s behavioral, sociodemographic, and anthropometric characteristics. 7 This study used data from the 2020 survey. The random countywide sample was augmented with additional random samples of Asian and Black families and families residing in target communities within LAC to ensure certain races and ethnicities were not underrepresented. The 2020 survey was approved by the California Health and Human Services Agency Committee for the Protection of Human Subjects, and this study was reviewed by the Institutional Review Board at California State University Fullerton (#HSR-20-21-460).
Sample
A total of 6753 surveys were completed (53% response rate). The sample was restricted to biological mothers who gave birth to the survey child within 1 year of the survey completion date (n = 1288). We then excluded mothers who were pregnant (n = 0) or provided implausible or missing pre-pregnancy or postpartum heights and weights (n = 157) because the outcome variable could not be calculated. Twin (n = 10) and preterm (n = 133) births were also removed because they had the potential to skew SPPWR values.2,8 The unweighted sample size was 988. Post-stratification weights were then applied to the sample to weigh respondents to the source population (i.e., April 2020 LAC WIC population) based on participant age, race/ethnicity, language preference, and service planning area (SPA). Only the LAC WIC population was used as the referent for calculating the weights. The final weighted sample size used for analysis was 1019.
Measures
Substantial postpartum weight retention was defined as the difference between the self-reported weight at the time of survey completion and the self-reported pre-pregnancy weight, with a dichotomized cut-off point at ≥5 kg. 4 This cut-off was selected for identifying women at risk of developing obesity.3-5
For this study, literature-supported risk factors were used as potential predictors of SPPWR.1-5,9,14,15 Demographic factors included child’s age (proxy for postpartum duration in months), mother’s age (years), race/ethnicity (“Hispanic Spanish-speakers”, “Hispanic English-speakers”, “White”, “Black”, “Asian”, and “Other”), education (“less than high school”, “completed high school”, “some college”, and “completed college or beyond”), employment status since having child (yes/no), and healthcare coverage (yes/no). Race/ethnicity and language preference were combined and coded as “Hispanic English-speakers” and “Hispanic Spanish-speakers” because Spanish- and English-speaking people of Hispanic origin exhibit different health behaviors. 10
Psychosocial factors included food insecurity, depressed mood, instrumental support (yes/no), emotional support (yes/no), and spouse’s participation in child’s life (yes/no). Food insecurity was assessed using the Six-Item Short Form Food Security Survey Module. 11 Using the US Department of Agriculture’s definitions of food security and food insecurity, high and marginal food security survey scores (0-1) were labeled as “no food insecurity” and low (2-4) and very low (5-6) food security survey scores were labeled as “food insecurity”. 12 Depressed mood was assessed using the Patient Health Questionnaire-2 (PHQ-2). 13 Sum scores ranged from 0-6, with 0-2 labeled “no” and 3-6 labeled “yes.”
Anthropometric and behavioral factors included pre-pregnancy BMI, GWG, gestational diabetes (yes/no), and any breastfeeding. Pre-pregnancy body mass index (BMI) was calculated by dividing the self-reported pre-pregnancy weight by the self-reported height squared (kg/m2). 2 Values were then grouped into the following categories: underweight (<18.5 kg/m2), normal (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obese (>30 kg/m2). 2 GWG was defined as weight gained during pregnancy. 2 According to the Institute of Medicine, GWG recommendations depend on pre-pregnancy BMI: 28-40 lbs for underweight women, 25-35 lbs for normal-weight women, 15-25 lbs for overweight women, and 11-20 lbs for obese women. 2 Participants that surpassed the upper end of their recommended GWG range were labeled as “exceeded GWG guidelines.” Any breastfeeding (months) was determined by using the child’s age for breastfeeding mothers and the age at which the child stopped breastfeeding for mothers who were not currently breastfeeding.
Analysis
All analyses were weighted to ensure the sample was representative of the LAC population and performed using SPSS version 28. Descriptive statistics were used to describe the sample’s characteristics and prevalence of SPPWR. Adjusted odds ratio (AOR) and 95% confidence intervals (CI) were computed using binary logistic regression to examine the relationship between SPPWR and the fifteen predictor variables.
Results
Weighted Descriptive Statistics of Study Sample with Substantial Postpartum Weight Retention Prevalence (N = 1019).
Abbreviations: SD, Standard Deviation; SPPWR, Substantial Postpartum Weight Retention; FSS, Food Security Survey; PHQ-2, Patient Health Questionnare-2.
aPercentages among non-missing. Missing responses <2%.
Regarding BMI status, the prevalence of overweight and obesity increased from 67.6% before pregnancy to 76.5% at the time of the survey (Table 1). Of the women who had a normal BMI prior to pregnancy, 38.4% were classified as overweight or obese at the time of the survey. Additionally, 32.7% of women who had an overweight pre-pregnancy BMI were obese at the time of the survey.
Weighted Binary Logistic Regression Model: Adjusted Odds Ratios for Experiencing Substantial Postpartum Weight Retention Within the First Postpartum Year.
Abbreviations: AOR, Adjusted Odds Ratio; CI, Confidence Interval; FSS, Food Security Survey; PHQ-2, Patient Health Questionnare-2.
*P < .05; ***P < .001.
Discussion
This study showed a higher prevalence (31%) of substantial postpartum weight retention (SPPWR) during the first postpartum year compared to other US-based studies (13%-20%).4,5 These results may be attributed to differences in sociodemographic and lifestyle factors among populations. However, more research on this topic is needed to truly understand how our sample compares to other populations. We also found that the child’s age (proxy for postpartum duration) was significantly associated with SPPWR, meaning that respondents who were further along in the first postpartum year were more likely to develop SPPWR. This result indicates that Southern California WIC mothers may be gaining weight during the postpartum period, which has been seen in other studies. 14 This finding warrants further investigation.
An unanticipated outcome was that respondents with overweight and obese pre-pregnancy BMIs were less likely than respondents with normal pre-pregnancy BMIs to experience SPPWR. In other populations, one study reported a similar finding 1 while another study found the opposite result. 15 One possible explanation for our finding is that, according to the Institute of Medicine guidelines, normal-weight women may have more weight to lose after delivery compared to overweight and obese women because they have a wider recommended range for GWG. Thus, normal-weight women may need more time to return to their pre-pregnancy weight. Future studies should explore SPPWR beyond 12 months postpartum to better understand the relationship between pre-pregnancy BMI and SPPWR in our sample.
Like other studies, mothers who gained above the GWG guidelines were more likely to have SPPWR in our study.1,4,5 Therefore, future research may benefit from exploring how interventions to prevent excessive GWG influence SPPWR in the Southern California WIC population.
Limitations of this study include that heights and weights from the 2020 LAC WIC Survey were self-reported, and thus, response bias could have affected the accuracy of the pre-pregnancy BMI and outcome variable. 4 Although self-reported data are not always accurate, a recent nationwide cohort study suggested that BMI determined from self-reported height and weight could function as a valid measure. 16 Nevertheless, future studies should investigate the agreement between self-reported and measured height, weight, and derived BMI in the Southern California WIC population. Another limitation is that the survey data was collected during the coronavirus disease 2019 (COVID-19) pandemic. Therefore, pandemic-related restrictions could have hindered respondents’ access to important WIC services such as breastfeeding and nutrition counseling. This, in turn, may have influenced our findings, but further investigation is needed to examine the impact of COVID-19 on SPPWR in our sample.
Ultimately, our findings suggest that interventions to prevent SSPWR among respondents should target at-risk women through preconception checkups and help them manage their weight throughout pregnancy and the postpartum period. The Wise Investment in Children Act of 2021, a bipartisan bill introduced to enhance access to WIC support for mothers and children, holds great potential to reduce SPPWR in the Southern California WIC population through its provision to extend postpartum eligibility to 2 years.
17
A longer postpartum period of WIC eligibility may give WIC providers the opportunity to focus on delivering interconception care and helping moms achieve healthy weight outcomes prior to a possible subsequent pregnancy. With obesity prevalence increasing in US women of reproductive age,4,5 tailored interventions and legislation such as the Wise Investment in Children Act may help Southern California WIC mothers maintain a healthy weight after pregnancy. Current literature suggests that substantial postpartum weight retention (SPPWR) is linked to the development of obesity later in life. However, few studies have explored the prevalence and determinants of SPPWR in low-income women from the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). The prevalence of SPPWR in our sample was higher (31%) than other US-based studies (13%-20%). We also found that pre-pregnancy body mass index (BMI), gestational weight gain, and postpartum duration can impact SPPWR in Southern California WIC mothers during their first year after childbirth. The postpartum period may serve as a window of opportunity for introducing interventions that could help reduce SPPWR in the Southern California WIC population. However, future investigations are needed to identify what, if any, barriers exist to postpartum weight loss among respondents. Furthermore, additional research is recommended to support our findings across other populations.So What?
What is already known on this topic?
What does this article add?
What are the implications for health promotion or research?
Footnotes
Acknowledgments
We thank the WIC staff for their contribution to this project and the participants for completing the 2020 Los Angeles County WIC Survey. HY was supported by Grant MHRT2T37D001368 from the National Institute on Minority Health and Health Disparities, National Institute of Health. The Los Angeles County WIC survey was funded by First 5 LA, a leading public grant-making and child advocacy organization (award number 07030).
Author Contributions
Conception and design of the work: HY and MK; data acquisition: SW; data analysis and interpretation: HY, MK, and SW; drafting the work and revising it for important intellectual content: HY, MK, and SW; approval of the version to be published: HY, MK, and SW; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved: HY, MK, and SW.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Minority Health and Health Disparities Research Training (MHRT) Program, National Institute on Minority Health and Health Disparities, National Institutes of Health (grant MHRT2T37MD001368). Funding was also provided by First 5 LA, a leading public grant-making and child advocacy organization (award number 07030).
