Prenatal exposure to tobacco smoke, through either active maternal smoking or secondhand exposure, has been associated with impaired fetal oxygenation, metabolic stress, and adverse early neonatal outcomes. This prospective, single-center observational cohort study will objectively assess maternal tobacco exposure using cotinine measured in maternal urine and examine its association with early neonatal biochemical, metabolic, and clinical outcomes.
Consecutive eligible mother-newborn dyads will be recruited at a tertiary academic hospital after written informed consent is obtained. A clean-catch midstream maternal urine sample will be collected within 24 hours before delivery, preferably at admission to the delivery unit and before intravenous fluid administration, for quantitative cotinine and creatinine measurement. Maternal tobacco exposure will be assessed using the urinary cotinine concentration, the cotinine-to-creatinine ratio, and maternal self-reported smoking and secondhand smoke exposure. Based on prespecified biomarker thresholds and exposure history, participants will be classified as having active exposure, passive exposure, or no exposure. No experimental intervention will be administered.
Neonatal data will include umbilical cord blood gas parameters, including pH, pCO2, pO2, base excess, bicarbonate, lactate, and fetal carboxyhemoglobin (FCOHb). Birthweight, length, head circumference, Apgar scores, oxygen saturation, heart rate, and blood pressure will also be recorded. Routine laboratory measurements obtained during the early postnatal period will include complete blood count parameters, hematologic and inflammatory indices such as NLR and PLR, albumin, the albumin-to-lactate ratio, HDL, LDL, and other routinely available biochemical markers. Thyroid-stimulating hormone results from the national newborn screening program and newborn hearing screening results will be recorded. Postnatal weight loss and bilirubin measurements from routine follow-up visits will also be collected when available.
The primary objective is to determine whether increasing maternal urinary cotinine exposure is associated with higher umbilical cord blood lactate and FCOHb levels, indicating greater metabolic stress and impaired fetal oxygenation. Secondary objectives include evaluating associations with cord blood gas parameters, birthweight, early hematologic and biochemical indices, albumin and the albumin-to-lactate ratio, blood pressure, bilirubin levels, thyroid screening results, and hearing screening outcomes.
Maternal, obstetric, and perinatal variables, including maternal age, parity, gestational age, mode of delivery, smoking history, intrapartum factors, and relevant maternal comorbidities, will be recorded for adjusted analyses. Statistical analyses will include comparisons among the three exposure groups and multivariable regression models evaluating urinary cotinine both as a continuous measure and as a categorical exposure variable.
This study is designed to provide prospectively collected, biomarker-verified evidence regarding the relationship between maternal tobacco exposure and immediate neonatal metabolic, hematologic, and physiologic outcomes using measurements that are feasible within routine clinical care.
Pregnant individual expected to deliver a liveborn infant at the study hospital and providing written informed consent before delivery.
Singleton pregnancy with an anticipated gestational age of ≥35 completed weeks at delivery.
Maternal clean-catch urine sample obtainable within 24 hours before delivery, preferably at admission and before intravenous fluid administration, for urinary cotinine and creatinine measurement.
Availability of routine umbilical cord blood gas analysis at birth, including at minimum lactate, pH, and base excess, with fetal carboxyhemoglobin recorded when available.
Multiple gestation.
Major congenital anomaly, known chromosomal or genetic disorder, or major metabolic disease likely to affect neonatal adaptation or the study outcomes.
Emergency clinical circumstances in which obtaining informed consent or the maternal urine sample could delay or interfere with urgent maternal or neonatal care.
Inability to obtain an adequate maternal urine sample before delivery for cotinine and creatinine measurement.
This is a single-center prospective cohort study conducted at a tertiary hospital. Consecutive eligible mother-newborn dyads are recruited during the delivery hospitalization. Maternal clean-catch urine is collected within 24 hours before delivery for cotinine and creatinine measurement. Dyads are classified as active exposure, passive exposure, or no exposure according to prespecified urinary cotinine-to-creatinine thresholds and maternal exposure history. Outcomes are obtained mainly from routine care and include cord blood lactate, pH, base excess, FCOHb, birthweight, anthropometric measurements, Apgar scores, vital signs, early laboratory results, newborn screening TSH, hearing screening, and follow-up weight loss and bilirubin where available. No experimental intervention or additional neonatal blood sampling is planned.
Cohort
Prospective
Maternal Urinary Cotinine Assessment
Other interventionA clean-catch midstream maternal urine sample will be collected within 24 hours before delivery, preferably at admission to the delivery unit and before intravenous fluid administration. Urinary cotinine and creatinine concentrations will be measured, and the cotinine-to-creatinine ratio will be used to objectively classify prenatal tobacco exposure. No treatment or behavioral intervention will be assigned.
Umbilical Cord Blood Lactate
Umbilical cord blood lactate concentration measured using routine blood gas analysis. Lactate levels will be compared across maternal urinary cotinine-defined exposure groups (active, passive, and no exposure) and evaluated in multivariable regression models with adjustment for relevant maternal and perinatal factors. Unit of Measure: mmol/L.
Umbilical Cord Blood pH
Arterial/venous cord blood pH per routine gas analysis; association with maternal cotinine exposure categories. Unit of Measure: pH units
Umbilical Cord Blood Base Excess (BE)
Base excess from routine cord gas; group comparisons and adjusted models parallel to primary analysis. Unit of Measure: mEq/L
Fetal Carboxyhemoglobin (FCOHb)
Percent carboxyhemoglobin from cord blood CO-oximetry; tested for dose-response with maternal urinary cotinine. Unit of Measure: percent
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