Edited by: Dora Il'yasova, Georgia State University, United States
Reviewed by: Cihad Dundar, Ondokuz Mayis University, Turkey; Figen Cavusoglu, Ondokuz Mayis University, Turkey
This article was submitted to Children and Health, a section of the journal Frontiers in Public Health
†ORCID: Harvey Ho
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
The first survey on SHS exposure in pregnant women that combines a questionnaire, objective saliva cotinine tests, and ultrasound flow index analysis has been performed in China;
29.44% of 548 participants reported SHS exposure of more than 15 min per day;
“Workplace” (42.15%) was the top venue where SHS exposure occurred;
The prevalence of 31 women detected SHS-exposure positive by saliva cotinine test was 25.8%;
Six (75%) participants whose saliva samples were detected SHS-exposure positive reported SHS exposure;
The mean PI in the SHS group is higher than that in the non-SHS group (1.10 vs. 1.02) in fetuses at 24 weeks' gestation.
China is the world's largest producer and consumer of tobacco, yet the prevalence of active smoking among Chinese women is about 3.84% (
Previous studies have shown the adverse effects of active or passive smoking on fetal health. For example, pregnant women exposed to smoking are more likely to have intrauterine growth restriction (IUGR) (
In view of the adverse effects of SHS exposure on fetal development, tobacco control policies and intervention guidelines need to be set forth in the communities and households of pregnant women. However, as pointed out by a recent survey of risk factors for cancers in 31 provinces of mainland China (
The primary aim of the study is to investigate the current SHS exposure situation among pregnant women in Chongqing, which is a metropolitan city in China with an urban population of 8.5 million and yet for which data for SHS exposure among pregnant women is lacking. Thus, we use a questionnaire-based approach to gain an overall picture of SHS exposure in this city. Since there are possible inaccuracies in self-reporting, we also experiment with a saliva cotinine kit for detecting SHS exposure among pregnant women—the first use of this kind of experiment in China. In addition, since flow indices of the umbilical artery (UA) are suggested to be a biomarker for pathological conditions of the placenta (
The study was performed at the Chongqing Health Center for Women and Children (CHCWC), Chongqing City, China. The center manages ~16,000 childbirths each year. The Ultrasound Department of the CHCWC was in charge of the study, including conducting questionnaire management, saliva cotinine sample tests, and fetal ultrasonic scans. A team of biomedical scientists at the University of Auckland, New Zealand, assisted with the questionnaire design and statistical analysis. At the first stage, pregnant women at the nuchal translucency (NT) period (12 ± 1 weeks) and 24 ± 1 weeks of gestation could voluntarily participate in the study by signing a consent form and self-reporting their SHS status. A subset of this participant group also had their saliva cotinine measured and arterial flow indices of their fetuses analyzed. The study was approved by the Ethics Committee of the CHCWC.
A questionnaire on SHS exposure was designed and implemented in a mobile phone application, namely, Wen Juan Xing (“Questionnaire Star”) on WeChat, a Chinese social media platform. Prospective participants could scan a QR code of the application and enroll in the study by signing an electronic consent form. The questions on demographic parameters include age (in years), education level (above or below tertiary education), family income (under or above RMB 150k), and drug use history during pregnancy, if any. The questions concerning SHS exposure include:
Did you smoke before pregnant? If yes, approximately how many cigarettes did you smoke per day? (above or below 10 cigarettes).
Have you smoked after becoming pregnant? If yes, approximately how many cigarettes do you smoke per day? (above or below 10 cigarettes).
Does your husband smoke? If yes, approximately how many cigarettes does he smoke per day? (above or below 10 cigarettes).
If you are exposed to secondhand smoke, where does it happen (multiple choices allowed): (a) Home; (b) Workplace; (c) Restaurant; (d) Public transportation; (e).
If you are exposed to secondhand smoke, approximately how many minutes would it be? (a) Under 15 min (no SHS exposure); (b) 15–30 min; (c) 15–60 min; (d) above 60 min.
Answers to these questions as well as the demographic data were analyzed by SPSSAU, a software package that comes with Wen Juan Xing, which has similar statistical algorithms as are used in SPSS (IBM, Inc.).
A saliva cotinine test kit (NicAlertTM, Confirm Bioscience, CA, USA) was used to quantitatively measure the cotinine level in saliva samples. As the major metabolite of nicotine, cotinine is often used as the biomarker of nicotine due to its much longer half-life (16 vs. 2 h) than nicotine (
For the purpose of proof-of-concept, a small subset of the participants was selected for saliva cotinine tests. The selection criteria included: (a) no anatomic abnormality detected in the fetus from ultrasonography imaging; (b) the mother had no underlying diseases, e.g., diabetes and hypertension. Furthermore, the sample should include a group of participants who self-reported SHS exposure and a control group who did not report exposure to SHS. The sample size was restricted by the availability of saliva kits, of which there were 50 when the tests were performed.
All survey participants underwent routine prenatal ultrasound scans in the Ultrasound Department of CHCWC; this was the main purpose of their hospital visits. From those participants who had their saliva samples measured, we retrospectively analyzed the flow indices revealed from Doppler sonography (GE VolusonTM E8). Previous studies have shown that exposure to active smoking affects the systole/diastole flow velocity ratio (S/D ratio) in fetal umbilical and middle cerebral arteries (
During the 4 months from July to November 2019, 548 pregnant women participated in the survey. Of these, 74.82% were at the NT stage (12 ± 1 weeks' gestation), and the rest were at 24 ± 1 weeks' gestation. The average age of the participants was 29 years (SD 4.1). The active smoking rate before pregnancy was 3.47%, similar to the published active smoking rate of 3.84% among Chinese women (
Demographic and SHS-related characteristics of participants (
Age (Mean) | 29 (4.1) |
Education (Below Tertiary), |
291 (53.1) |
Annual income (< RMB150k) |
358 (65.33) |
Trimester 1 (0–12wk), |
410 (74.82) |
Smoking pre-pregnancy, |
19 (3.47) |
Smoking during pregnancy, |
1 (0.18) |
Partner being a smoker, |
239 (43.61) |
SHS exposure at home, |
102 (18.61) |
SHS exposure time (<15 min), |
387 (70.62) |
SHS exposure time (<30 min), |
524 (95.62) |
Saliva cotinine levels were measured in 31 participants. All 23 (100%) pregnant women who tested SHS-exposure negative (i.e., saliva cotinine readings were zero) also self-reported the same. Among the eight participants whose saliva samples tested SHS-exposure positive (i.e., saliva cotinine readings were one or above), six (75%) reported SHS exposure of more than 15 min. However, two (25%) self-reported as negative for SHS exposure in the questionnaire.
Among the pregnant women who had their saliva cotinine level measured, the flow indices of the fetuses of 23 of them were available for analysis. Eight of the 23 women had fetal ultrasound data at both 12 ± 1 and 24 ± 1 weeks' gestation. For this group, the PI at 24 ± 1 weeks had a mean of 1.03 (SD 0.12), lower than the PI at 12 ± 1 weeks' gestation, 3.39 (1.12). The abnormally high PI of the latter resulted from reversed diastolic flows (
The comparison between the PI of the SHS-exposure positive and negative groups is listed in
The mean value and standard deviation of the flow indices of PI.
12 ± 1 ( |
2.97 (0.85) |
24 ± 1 ( |
1.10 (0.27) |
12 ± 1 ( |
4.41 (3.23) |
24 ± 1 ( |
1.02 (0.11) |
Exposure to active or passive smoking during pregnancy is associated with many detrimental effects on fetuses, including restricted fetal growth, stillbirth, preterm delivery, and sudden infant death syndrome, to name a few (
There are several novelties in the implementation of this study. Firstly, a mobile phone-based application was used to collect and analyze the data from the questionnaire, taking advantage of the ubiquity of mobile phones in present-day China. Unlike a paper-based questionnaire, a user could complete the survey at any time and any location at her convenience. Secondly, this work represents the first study using saliva cotinine strips for objective cotinine measurements among pregnant women in China. Saliva cotinine strips have been used in studies in New Zealand (
Previous studies suggested that up to 35% of pregnant women might self-report inaccurately due to embarrassment or shame (
Thirdly, the analysis for flow indices in fetuses started at the NT period, i.e., end of the first trimester, whereas most of the literature reports flow index data from middle to late gestation, e.g., 34–35 weeks in (
There are limitations pertaining to the current study. Firstly, while 548 pregnant women took part in the SHS survey, only a small portion of the participants received saliva cotinine tests, and only 8 of the 23 women had fetal ultrasound data at both 12 ± 1 and 24 ± 1 weeks' gestation. A larger sample size is required to verify the findings of this preliminary investigation. Secondly, pregnant women in their first and second semesters were selected in this pilot study because of the timeframe (Jul–Nov 2019), and we could longitudinally trace the pregnant women in the third trimester in future studies. In addition, some essential data, e.g., the efficacy of the saliva cotinine kit, were required that would help us to design the questionnaires of the ensuing series. Interestingly, ultrasound data for UAs from the literature were mainly collected from pregnant women in the late second and the third semester (
In conclusion, the results and data from this pilot study are not only valuable for guiding our ensuing studies on SHS exposure but may also be useful as a reference for public health workers for the implementation of SHS intervention in public places.
The datasets generated for this study are available on request to the corresponding author.
The studies involving human participants were reviewed and approved by The Ethics Committee of the Chongqing Health Center for Women and Children. The patients/participants provided their written informed consent to participate in this study.
JT: Survey questionnaire design, fetal ultrasound scan, and analysis. JS: Data collection, saliva cotinine tests, and fetal ultrasound scan. SR: Fetal ultrasound scan and project management. HH: Survey questionnaire design, ultrasound data analysis, and paper drafting. SZ: Statistical analysis and paper drafting. All authors: reviewed and agreed the paper.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.