Gestational weight gain outside the 2009 Institute of Medicine recommendations: novel psychological and behavioural factors associated with inadequate or excess weight gain in a prospective cohort study

For nursing students

Study summary

Gaining too little or too much weight during pregnancy is common, and it matters for the health of both mother and baby. In 2009, the U.S. Institute of Medicine (IOM) published guidelines that recommend a specific weight-gain range based on a woman's pre-pregnancy body mass index (BMI). Most research on why women fall outside these ranges has focused on physical, demographic, and obstetrical factors like age, income, or parity. This Canadian prospective cohort study, published in BMC Pregnancy and Childbirth, asked a different question: do psychological and behavioural factors, such as anxiety, body image, and eating habits, also predict inadequate or excess gestational weight gain (GWG)?

Researchers recruited 970 English-speaking women carrying a single baby, between 8 and 20 weeks of gestation, from 12 obstetrical, family medicine, and midwifery clinics in Ontario. At an average of 14.8 weeks of pregnancy, participants completed a questionnaire covering demographic, physical, obstetrical, psychological (such as anxiety, body attitudes, and self-efficacy), and behavioural factors (such as eating in front of a screen, eating alone, and food cravings). Total weight gain across pregnancy was later classified as inadequate, appropriate, or excess according to the 2009 IOM guidelines, and researchers used stepwise multinomial logistic regression to identify which factors predicted each outcome, using appropriate gain as the comparison group.

More than half the sample (55.4%) gained excess weight, 15.9% gained inadequately, and only 28.8% landed within the recommended range, underscoring how common guideline-discordant gain is. For inadequate GWG, the strongest predictor was a diagnosis of anxiety, followed by pre-pregnancy obesity, planning to gain weight below the guidelines (or not reporting a plan), and a pattern of eating sensibly around others but overeating alone. Two factors appeared protective against inadequate gain: having frequent pregnancy-related food cravings and preferring a larger body-size image. For excess GWG, pre-pregnancy overweight status was the strongest predictor, followed by pre-pregnancy obesity, planning to gain above the guidelines, frequent eating in front of a screen, and the same alone-overeating pattern seen with inadequate gain. Being underweight before pregnancy was protective against excess gain. Notably, obesity before pregnancy and solitary overeating showed up as risk factors for both inadequate and excess gain, highlighting how the same behaviour or body status can push weight gain in different directions depending on other factors.

For nursing students, this study is a reminder that prenatal weight counselling cannot rely only on checking a scale and comparing it to a chart. The authors argue that anxiety and body-image preferences are under-recognized levers that could be addressed alongside traditional counselling about diet and exercise. They also point out something clinically useful: women who did not report having a specific weight-gain plan were more likely to gain inadequately than even those who planned to gain below the guidelines, which suggests a gap in prenatal counselling that nurses and midwives are well positioned to close by proactively discussing individualized GWG targets early in pregnancy, rather than assuming women already understand them.

The study does have real limits. Only 15.9% of participants gained inadequately, which reduced the statistical power available to detect predictors in that group, so those findings should be interpreted cautiously. The sample was also drawn from women with relatively high education and household income, which limits how confidently the findings generalize to more socioeconomically diverse or non-English-speaking populations. Because this was an observational cohort study, none of the associations described can be interpreted as cause-and-effect; anxiety, for instance, might influence eating and weight gain, or unhealthy weight trajectories could contribute to anxiety, or a third factor could drive both.

Still, the study adds a useful, source-grounded piece to the puzzle of why gestational weight gain so often falls outside IOM recommendations. It supports moving prenatal counselling beyond a purely physical framework toward one that also screens for anxiety, eating patterns like screen-based or solitary overeating, and unspoken assumptions about ideal body size, since these were identified as modifiable, teachable targets rather than fixed patient characteristics.

For educators

Teaching and appraisal notes

This prospective cohort study (Feng, Yu, van Blyderveen, Schmidt, Sword, Vanstone, Biringer, McDonald, Beyene & McDonald, 2021, BMC Pregnancy and Childbirth) extends the gestational weight gain (GWG) literature by testing psychological and behavioural predictors alongside the traditional physical, demographic, and obstetrical variables typically studied against the 2009 Institute of Medicine (IOM) guidelines. The design is well suited to classroom discussion of how observational cohort methodology, multinomial logistic regression, and psychosocial measurement intersect in perinatal research.

Methodologically, 970 English-speaking women with singleton pregnancies were recruited at 8-20 weeks gestation from 12 obstetrical, family medicine, and midwifery clinics (baseline data collected at a mean 14.8 ± 3.4 weeks). A comprehensive baseline questionnaire assessed cognitive (body attitudes, self-efficacy, dietary restraint), affective (depression, anxiety), and personality domains, plus behavioural variables such as screen eating, solitary overeating, sleep, physical activity, and cravings. Total GWG, abstracted from antenatal records, was classified per IOM categories, and stepwise multinomial logistic regression (entry p<0.10, retention p<0.05) modeled predictors of inadequate and excess gain against an appropriate-gain reference group.

The outcome distribution itself is instructive for class discussion: only 28.8% of the cohort achieved appropriate GWG, while 55.4% gained excessively and 15.9% gained inadequately — a strong empirical illustration of how common guideline-discordant gain is even in a relatively advantaged, well-resourced sample. For inadequate GWG, anxiety diagnosis emerged as the strongest adjusted predictor (aOR 3.65, 95% CI 1.84-7.28), followed by not reporting a weight-gain plan (aOR 3.15), pre-pregnancy obesity (aOR 2.35), planning to gain below guidelines (aOR 2.16), and solitary overeating (aOR 1.62); frequent food cravings (aOR 0.53) and preference for a larger body-image ideal (aOR 0.26) were protective. For excess GWG, pre-pregnancy overweight status was the strongest predictor (aOR 2.39), followed by planning to gain above guidelines (aOR 2.19), frequent screen eating (aOR 1.93 for some meals, 1.85 for most/all meals), pre-pregnancy obesity (aOR 1.71), and solitary overeating (aOR 1.51); pre-pregnancy underweight was protective (aOR 0.35). Obesity and solitary overeating were shared risk factors across both discordant categories, suggesting overlapping mechanistic pathways worth highlighting to students studying multinomial outcome modeling.

Discussion points worth raising with students: the authors interpret the anxiety-inadequate GWG link through a sympathetic-adrenal-medullary framework (acute stress suppressing appetite) as distinct from chronic-stress models of weight gain, and they frame screen eating through the distracted-eating literature on satiety cues. The finding that women without a reported weight-gain plan had higher odds of inadequate gain than those planning below-guideline gain is a strong prompt for discussing prenatal counselling gaps and the modifiability of planning-based interventions.

Critical appraisal should center on two author-acknowledged limitations: the inadequate-GWG subgroup was small (15.9%, n≈154), reducing statistical power for that comparison, and the cohort skewed toward higher education and household income, limiting generalizability to more diverse or lower-resource populations. As with any cross-sectional-style baseline questionnaire linked to a later outcome, temporality and residual confounding (e.g., unmeasured depression severity, food insecurity) should be raised as threats to causal interpretation. This paper pairs well with seminar discussion on distinguishing statistically significant psychosocial predictors from clinically actionable counselling targets, and on how nursing and midwifery practice might operationalize anxiety screening and eating-pattern assessment within existing prenatal visit structures without adding undue burden.