In a recent study, rates of severe nausea and vomiting of pregnancy were higher in passive smokers than non-smokers.
Maternal exposure to second-hand smoke may increase the risk of severe nausea and vomiting of pregnancy (NVP), according to a recent study published in Heliyon.
NVP is the most commonly observed medical symptom caused by pregnancy, with over 90% of pregnant women experiencing NVP early in pregnancy. It commonly presents at 4 to 9 weeks of pregnancy, with the most severe symptoms at 7 to 12 weeks.
NVP may lead to physical and mental discomfort, along with a financial burden. Severe NPV can cause dehydration, electrolyte imbalance, weight loss, and potential hospitalization from vomiting. Hyperemesis gravidarum may also appear in women with severe NVP, potentially causing maternal and fetal morbidity if left untreated.
While the factors which cause NVP are not completely defined, a link has been made between maternal active smoking and NVP risk. However, the risk from passive smoking is unclear.
To determine the association between passive smoking in pregnant women and NVP risk, investigators conducted a study using data from pregnant women in Beijing, China. The initial study where baseline data was gathered from was a population-based prospective cohort study conducting prenatal check-ups in early-pregnant women.
Participants were recruited from October 2017 to May 2019. Inclusion criteria included being aged at least 18 years, not having significant lifestyle or habit changes in the past year, being within 14 years of pregnancy, planning to give birth in the study hospital, and consenting to participation. A total of 3533 participants were included.
Data collection in pregnant women occurred onsite, and trained professionals gathered information from 3 months prior to pregnancy to the first trimester. Information collected included sociodemographic characteristics, obstetric characteristics, disease history, eating habits, lifestyle, environmental exposure, and emotional conditions.
Women were asked, “Have you experienced severe nausea and vomiting during early pregnancy accompanied by urinary ketone positive?” and could answer yes or no. Aggravated vomiting in early pregnancy and ketonuria were used to define severe NVP.
The lifestyle portion of the questionnaire was used to obtain data on active and passive smoking in early pregnancy. Women exposed to cigarette smoke for 15 minutes at least once weekly in early pregnancy were defined as passive smokers. Active smokers and women who had smoked in the previous month were excluded from the analysis.
There were 3064 participants in the final analysis, 7.4% of which reported passive smoking and 9.8% severe NVP in the first trimester. Demographic characteristics did not differ between women with and without severe NVP, though lower levels of education on average were seen in women with severe NVP.
The rate of passive smoking was 12% in the severe NVP group compared to 6.9% in the non-symptom group, showing a positive association between passive smoking and severe NVP. Severe NVP had a crude odds ratio (OR) of 1.85 for passive smokers and an adjusted OR of 1.62. A significant trend was found through linear-by-linear association.
Passive smoking was also found to be a significant severe NPV risk factor among nulliparous women, with an OR of 1.87. Multiparous women did not share this risk, with an OR of 0.73. Participants with a high school or lower education status had an OR of 3.38, while those with a college level or higher education had an OR of 1.53.
Overall, passive smoking was associated with a significantly increased risk of severe NVP. Investigators recommended public health campaigns be put into place to avoid passive smoking during pregnancy.
Liu Y, Li Z, Li N.Effects of passive smoking on severe nausea and vomiting of pregnancy among urban Chinese nonsmoking women. Heliyon. 2023;9(4).doi:10.1016/j.heliyon.2023.e15294