(P27-018-25) Determinants of Low Birth Weight: Physiological, Anthropometric, and Sociodemographic Factors in Mexican Adolescent Mothers

Objectives: Adolescent pregnancy is a public health concern with significant repercussions for mothers and infants, including low birth weight (LBW) as a complication. Short gynecological age and younger maternal age are hypothesized risk factors, but their influence remains unclear in Mexican populations, where adolescent pregnancies account for 1 in 5 births. This study aimed to evaluate the relationship between chronological age, gynecological age, age at menarche, anthropometry, and sociodemographic factors on the birth weight of infants born to Mexican adolescents.

Methods: This follow-up study included 1,882 participants: 1,242 adolescents under 19 years and 640 adults. Anthropometric, sociodemographic, and clinical data were collected. Gynecological age was calculated, and hemoglobin levels were measured during the third trimester. Birth weight was extracted from clinical records and categorized using INTERGROWTH-21st tools. Logistic regression analysis was performed. Informed consent and assent were obtained.

Results: Newborns of adolescents under 19 years had a mean birth weight of 2.891 kg (30th percentile) vs. 2.993 kg (37th percentile) for adults. Neonates of adolescents aged 12–13 years were in the 28th percentile, compared to 38th for women aged 20–34 years (p=0.005). A gynecological age < 3 years corresponded to a gestational age percentile of 26 vs. 31 for 4 years and 35 for ≥5 years post-menarche (p=0.008).

LBW was linked to inadequate weight gain (OR: 1.82; CI: 1.04–3.20), hemoglobin < 11.5 g/dL (OR: 2.61; CI: 1.35–5.06), very low socioeconomic status (OR: 2.20; CI: 1.02–3.68), and living >50 km from the hospital (OR: 2.48; CI: 1.38–4.46). Early menarche (≤11 years) had a protective effect (OR: 0.51; CI: 0.26–0.98), but gynecological age showed limited association.

Conclusions: Anemia, inadequate gestational weight gain, and socioeconomic and geographic challenges significantly contributed to LBW. Early menarche appeared protective, while gynecological age had minimal impact. Addressing biological and social determinants is essential for preventing LBW.

Funding Sources: Funded by the Instituto Nacional de Perinatología, México.