**Background:** Adolescent pregnancy accounts for over 90% of teenage pregnancies worldwide and is associated with adverse maternal and neonatal outcomes. Between 56% and 84% of pregnant adolescents have inappropriate gestational weight gain (GWG), either insufficient or excessive. Despite established guidelines from the Institute of Medicine (IOM) for GWG in adults, factors associated with GWG in adolescents remain poorly understood. This scoping review aimed to synthesize evidence on individual, family, and sociocultural factors associated with inappropriate GWG in pregnant adolescents.
**Methods:** The review followed PRISMA guidelines and was derived from a protocol approved by the Instituto Nacional de Perinatología in Mexico City (2017-2-101 INPer CONACyT FOSSIS SALUD-2018-01-A3-S-40575). Eligible studies were original observational articles published since 1990, including adolescents aged 10–19 years, with GWG defined as increase in body weight during pregnancy in kilograms or pounds or assessed in categories. Databases searched included MEDLINE, Scopus, Web of Science, and Google Scholar. Two authors independently assessed study quality using a 14-question NIH tool (scores: 12–14 high, 9–11 good, 7–8 fair, <7 poor). Cohen's weighted kappa for inter-rater agreement was 0.924.
**Key Results:** From 842 titles, 13 studies were included: 6 retrospective cohorts (n=1571 adolescents), 3 prospective cohorts (n=568), 1 case–control (n=165), 1 cross-sectional (n=395), and 2 nationally representative US samples (n=78,001). Most studies were from the USA, followed by Mexico, Turkey, and Colombia. The frequency of excessive GWG among adolescents ranged from 38% to 50%, while inadequate GWG ranged from 18% to 34%; thus 56–84% had inappropriate GWG, with only one-third achieving adequate GWG.
**Individual factors:** Six studies found that higher pre-pregnancy body mass index (pBMI) was positively associated with excessive GWG. For example, Elchert et al. (2015) reported that 59.8% of adolescents <15 years, 59.9% of those 15–17 years, and 62.6% of those 18–19 years had excessive GWG. Cunningham et al. (2018) found excessive GWG in 50% of participants, with pBMI positively associated. Ekambaram et al. (2018) reported excessive GWG in 53% overall, ranging from 33% in underweight to 77.8% in obese adolescents (p<0.001). Three studies found no association when GWG was analyzed as a continuous variable. Chronological age was not associated with GWG in one study (Groth et al., 2008). Parity was associated with GWG in one US study (Chu et al., 2009): excessive GWG was 20.1% in primiparous vs. 10.8% in those with ≥3 births (p<0.001), but no association was found in a Turkish study. Energy intake adequacy was not associated with GWG in one Mexican study (Sámano et al., 2017). Serum leptin from the last trimester was positively associated with GWG (R²=0.177, p<0.001). Leptin, insulin, and HOMA-IR were correlated with pBMI but not directly with GWG in a Colombian study (Noreña et al., 2018).
**Family factors:** One Mexican cross-sectional study (Sámano et al., 2019, n=352) found that family support network size (by quartiles) was associated with GWG (p=0.003) but showed a non-linear trend. Another Mexican study (Sam-Soto et al., 2015, n=165) reported that adolescents with a history of sexual abuse had significantly lower mean GWG (7.5 kg vs. 12.5 kg, p=0.005).
**Sociocultural factors:** Race/ethnicity was examined in three US studies. Only one (Cunningham et al., 2018) found that Latina adolescents had a higher frequency of inappropriate GWG compared to other groups. No studies addressed other sociocultural factors such as income, education, or food security in relation to GWG.
**Clinical Implications:** pBMI is the most consistently identified factor associated with GWG in pregnant adolescents, particularly when GWG is assessed according to IOM categorical guidelines. Health personnel should assess pBMI using age- and sex-specific charts (WHO or CDC) for adolescents, especially those under 15 years. Excessive GWG may contribute to postpartum weight retention lasting up to 18 years after first pregnancy, perpetuating obesity across generations. The review identified critical research gaps: no studies on psychological states (depression, anxiety, stress), physical activity, or genetic variants (e.g., LEPR, FTO, MC4R polymorphisms) in relation to GWG in adolescents. Only two studies examined hormonal factors (leptin, insulin, adiponectin). Future research should focus on hormonal and genetic determinants, physical activity, nutrient intake, and validated tools for dietary and psychological assessment in pregnant adolescents.