Pregnancy outcome and cord blood cotinine level: A cross-sectional comparative study between secondhand smokers and non-secondhand smokers

OBJECTIVE: To compare the pregnancy outcome and cord blood cotinine levels between secondhand smokers and non-secondhand smokers.

STUDY DESIGN: This was a cross-sectional comparative study in a Malaysian tertiary obstetric hospital involving 200 non-smoking pregnant women at term, of whom 100 were secondhand smokers and 100 were non-secondhand smokers. Those with multiple pregnancies, with a body mass index (BMI) of more than 30kg/m2or who delivered by Caesarean section were excluded. The participants' basic demographic details, delivery details, neonatal outcome and placental weight were recorded. Umbilical cord blood samples were obtained, and cord blood cotinine levels were measured with a Cotinine ELISA kit. The primary outcomes were baby's birth weight, length, and head circumference, Apgar score at 5min and placental weight. The secondary outcome was difference in cord blood cotinine levels between the two groups and the correlation of these differences with the neonatal outcome.

RESULTS: The secondhand smoker group had significantly lower baby weight (2.94±0.31kg vs 3.05±0.40kg), head circumference (30.87±2.35cm vs 37.13±2.36cm), length (46.58±1.95cm vs 51.53±2.05cm) and placental weight (520±73.5g vs 596±61.3g) and significantly higher cord blood cotinine levels (16.35±12.84ng/mL vs 0.56±0.22ng/mL). Cord blood cotinine levels had significant negative correlations with placental weight (r=-0.461), baby's weight (r=-0.297), baby's head circumference (r=-0.501) and baby's length (r=-0.374).

CONCLUSION: Secondhand smoke increases the incidence of adverse pregnancy outcomes (newborns'anthropometric measurements and placental weight) and causes higher cord blood cotinine levels.