Maternal Smoking Exposure and Newborn Outcomes: A Study Using Cord Blood Cotinine

Overview

Prenatal exposure to tobacco smoke, whether from active maternal smoking or secondhand exposure, has been associated with adverse neonatal adaptation, metabolic stress, and impaired fetal oxygenation. This single-center prospective observational cohort study will quantify prenatal tobacco exposure using cord blood cotinine measured at delivery and examine its association with early neonatal biochemical, metabolic, and physiologic outcomes. Participants will consist of mother-newborn dyads recruited consecutively at a tertiary academic hospital. After informed consent, cord blood obtained at delivery will be used for cotinine measurement. Based on pre-specified cotinine thresholds and maternal smoking history, newborns will be classified into three exposure groups: active exposure, passive exposure, or no exposure. No experimental intervention will be administered, and neonatal assessments will be based on routine perinatal and postnatal care. Neonatal data collected will include umbilical cord blood gas parameters (pH, pCO2, pO2, base excess, bicarbonate, and lactate), fetal carboxyhemoglobin (FCOHb), birthweight and anthropometric measurements, Apgar scores, oxygen saturation, heart rate, blood pressure, and routine laboratory indices obtained during the first postnatal day. These laboratory measures may include complete blood count parameters, inflammatory and hematologic ratios such as NLR and PLR, metabolic markers including albumin and lactate-to-albumin ratio, lipid parameters such as HDL and LDL, thyroid-stimulating hormone from the standard newborn screening program, and hearing screening results. Early follow-up data, including postnatal weight loss and bilirubin measurements at routine visits, will also be recorded where available. Maternal and perinatal covariates, including maternal age, parity, gestational age, delivery mode, intrapartum factors, smoking history, and relevant maternal comorbidities, will be collected to support adjusted analyses. The primary objective is to determine whether higher cord blood cotinine-defined exposure is associated with greater metabolic stress and impaired fetal oxygenation at birth, particularly as reflected by cord lactate, related blood gas parameters, and FCOHb. Secondary objectives include evaluating associations with early neonatal hematologic, metabolic, endocrine, and clinical indices, including birthweight, blood pressure, bilirubin levels, thyroid screening results, and hearing screening outcomes. The study will recruit consecutive eligible dyads in a prospective manner. Statistical analyses will follow a pre-specified plan and will include multivariable regression models to adjust for potential confounding factors. Sensitivity and subgroup analyses, including analyses by delivery mode and other clinically relevant strata, will be performed when feasible. This study is designed to provide prospectively collected, biochemically verified evidence on how prenatal tobacco exposure, classified by cord blood cotinine, relates to immediate neonatal metabolic, hematologic, and physiologic outcomes using measurements that are feasible within routine clinical care.