WHO South-East Asia Journal of Public Health
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 Table of Contents  
PERSPECTIVE
Year : 2012  |  Volume : 1  |  Issue : 3  |  Page : 232-238

Pesticide exposure during pregnancy and low birth weight


1 Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City, Tennessee, United States of America
2 Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University; Department of Family Medicine, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, United States of America
3 School of Public Health, Shandong University, Jinan, Shandong, People's Republic of China

Date of Web Publication25-May-2017

Correspondence Address:
Liang Wang
Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City, Tennessee
United States of America
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DOI: 10.4103/2224-3151.207019

PMID: 28615549

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  Abstract 


Background: Limited epidemiologic studies have investigated the effects of pesticide exposure during pregnancy on low birth weight in offspring in rural China.
Methods: A survey of a total of 503 women was conducted in Ling county of Shandong Province of China following delivery from 1 November 2009 to 8 February 2010.
Results: After adjustment for confounding and compared with no pesticide exposure, multiple logistic regression showed a non-significant increased likelihood of low birth weight for both children of mothers exposed to pesticides when not pregnant (OR = 1.80, 95% CI: 0.62, 5.22) and mothers exposed to pesticides during pregnancy (OR = 2.42, 95% CI: 0.73, 8.08); multiple linear regression showed a non-significant reduced birth weight for both children of mothers exposed to pesticides when not pregnant (β=–0.59, p=0.28) and mothers exposed to pesticides during pregnancy (β=–0.89, p=0.15).
Conclusions: Exposure to pesticides during pregnancy was associated with a non-significant increase in low birth weight in this rural Chinese population. Future studies using larger sample sizes and longer follow-up periods are warranted.

Keywords: Pesticide, pregnancy, low birth weight.


How to cite this article:
Wang L, Wu T, Liu X, Anderson JL, Alamian A, Fu M, Li J. Pesticide exposure during pregnancy and low birth weight. WHO South-East Asia J Public Health 2012;1:232-8

How to cite this URL:
Wang L, Wu T, Liu X, Anderson JL, Alamian A, Fu M, Li J. Pesticide exposure during pregnancy and low birth weight. WHO South-East Asia J Public Health [serial online] 2012 [cited 2018 Aug 16];1:232-8. Available from: http://www.who-seajph.org/text.asp?2012/1/3/232/207019




  Introduction Top


Potential health effects associated with exposure to pesticides during pregnancy have become a major public health concern due to the widespread use of pesticides and the high sensitivity of the fetus and the pregnant mother to toxic exposures.[1] Pesticides are substances intended for preventing, destroying, repelling or mitigating pests such as insects, as well as fungi, vegetation, and rodents.[2] The global consumption of pesticides every year is approximately 2 million tons, of which one quarter is consumed in the United States of America (USA), about half in Europe, and one quarter in the rest of the world.[3] In the USA, pesticide usage in both 2006 and 2007 exceeded 1.1 billion lbs (~500 000 tons).[4] In Brazil, an estimated 113 993 tons of active ingredients in the pesticide were consumed in 1997.[5] In China, it has been reported that over 300 000 tons of pesticides are used in agriculture every year.[6] Skin contact and inhalation are the main routes for the absorption of pesticides into the body. The few epidemiologic studies that have investigated the effects of pesticide exposure on pregnancy outcomes, including low birth weight, have had inconsistent findings.[7] These different findings might be explained by variation in subject characteristics, difference in biomarkers used to identify exposure, and differences in the time windows of exposure assessed during pregnancy.[8],[9],[10],[11] Compared with non-farming residents, farmers, farm workers, and families living in agricultural regions are more likely to be exposed.[12],[13],[14],[15] Agricultural pesticide application is a major source of pesticide exposure. Women residing in rural areas are expected to be at much higher risk. Although studies have been conducted in developed countries, such as the USA,[16],[17],[18] Denmark,[19] Poland[20] and France[21], as well as in developing countries such as Mexico[22] and Brazil[23], to date, few studies have investigated exposure to pesticides and the possible adverse pregnancy outcomes, including low birth weight, in rural China. Although China has a relatively low incidence of low birth weight (6%) compared with other countries, it does have a considerable number of low birth weight births due to its large population.[24] A recent study in China that was based on a small urban sample size (n=187) found no association between pesticide exposure during pregnancy and low birth weight.[25] The purpose of our study was to use a much larger rural sample size to: (1) describe the amount of exposure to pesticides during pregnancy among women in Ling County of China; and (2) examine whether children of women who were exposed to pesticides during pregnancy were more likely to have low birth weight than children of unexposed women.


  Methods Top


Study site and participants

Study participants were recruited from Ling County People’s Hospital of Dezhou City in Shandong Province of China. The hospital is a major medical facility and provides broad medical services including perinatal care to residents in agricultural regions. The interviewers were two graduate students from the School of Public Health of Shandong University and several nurses from the hospital. The interviewers’ training was conducted by Professors Maosun Fu and Jun Li. A total of 1006 mothers, who were admitted to the hospital for delivery and gave live birth from 1 November, 2009 to 8 February 2010, were eligible for the study. A total of 503 mothers were excluded due to their reluctance to the study, and the rest of the mothers (50% response rate) completed the study questionnaire and were included in the final analysis. Informed consent was obtained from all study participants. The study protocol was approved by the Medical Ethics Committee of the School of Public Health, Shandong University.

Study variables

Outcome

Birth weight in grams was obtained from medical charts. Low birth weight was defined as less than 2500 grams, consistent with published standards.[24]

Exposure to pesticides during pregnancy

A questionnaire distributed to mothers shortly after their deliveries was used to collect information on pesticide-related exposures during pregnancy. The following question was asked of the mothers: “During your lifetime, have you ever personally mixed or applied any pesticides? (Include crop, livestock and structural insecticides, herbicides, fungicides and fumigants, pesticides used for farm use, and commercial application and personal use in your home or garden.)” If the answer to the foregoing question was yes, mothers were then asked the following question: “Did you personally mix or apply any pesticides during the different periods (such as first three months, middle three months, and/or last three months of pregnancy)?” The number of days of pesticide use exposure during pregnancy was determined for the first three months, middle three months, and last three months of pregnancy. However, the sample sizes of mothers exposed to specific pesticides and at different stages of pregnancy were not large enough to allow valid analyses for the different trimesters. Therefore, the exposure to pesticide use was defined according to the following three categories: (1) never exposed to pesticides; (2) exposed to pesticides when not pregnant; and (3) exposed to pesticides during pregnancy.

Covariates

Mother’s characteristics included race (Han, minority), the location of residence (rural, not rural), education (elementary school or below, middle school or above), age, gestational age at delivery [36 weeks or less (preterm), 37 weeks or above (not preterm)][26], and age at the start of having menstrual periods. Child’s sex (male, female) was recorded at birth.

Data analysis

Characteristics of the study population were described using proportions and means with standard deviation. Multiple logistic regression was used to estimate the odds ratios of exposure to pesticides after adjusting for covariates. Multiple linear regression was used to examine the relationship between pesticide exposure during pregnancy and the birth weight in grams as a continuous variable. All statistical analyses were performed using SAS, version 9.2 (SAS Institute, Inc., Cary, NC).


  Results Top


Maternal and newborn characteristics are shown in [Table 1]. Maternal average age was about 27 years (range 15–46). There were 18.3% preterm births and 4.2% low birth weight. Most mothers were of the Han race (95.6%) and lived in rural areas (94.4%). Approximately 85% of mothers had a middle school education or above. About half of all mothers were never exposed to pesticide use in their lifetime, 33.8% were exposed to pesticides while not pregnant, and 17.1% were exposed to pesticides during pregnancy.
Table 1: Maternal and child's characteristics after delivery

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The results of multiple logistic regression, shown in [Table 2], showed that compared with non-exposed mothers, children of mothers exposed to pesticides while not pregnant had a non-significant increased likelihood of low birth weight (odds ratio (OR) = 1.80, 95% confidence interval (CI): 0.62, 5.22) as did the children of mothers who were exposed to pesticides during pregnancy (OR = 2.42, 95% CI: 0.73, 8.08). A preterm child was about five times more likely to have low birth weight (OR=5.18, 95% CI: 2.01, 13.35) compared with a child that was not preterm. Increasing maternal age was associated with a reduced risk of low birth weight (OR=0.87, 95% CI: 0.77, 0.98). Multiple linear regression with birth weight as a continuous outcome variable was used to see whether the results would change given the small sample of children with low birth weight (n=21), and found the same results. Compared with children of mothers who were never exposed to pesticides, children of mothers who were exposed to pesticides while not pregnant showed a non-significant reduced birth weight (β= –0.59, p=0.28), as did the children of mothers who were exposed to pesticides during pregnancy (β= –0.89, p=0.15). Preterm was associated with reduced birth weight (β= –1.65, p<0.001). Increasing maternal age was associated with increased birth weight (β=0.14, p=0.02).
Table 2: Relationship between pesticide exposure during pregnancy and birth weight after adjusting for maternal and child's characteristics

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  Discussion Top


The potential health effects associated with exposure to pesticides during pregnancy are an important public health concern. The risk of adverse reproductive outcomes related to pesticide exposure has been investigated in only a few studies and the findings regarding the effect of exposure to pesticides during pregnancy on birth weight is limited and inconclusive.[27] The present study evaluated the role of exposure to pesticides during pregnancy on birth weight among women in an agricultural district in rural China and did not find a significant association between pesticide exposure during pregnancy and low birth weight. However, there was a non-significant increased risk of low birth weight associated with pesticide exposure. These findings are consistent with studies in France[21] and some studies in the USA,[8],[18] but not consistent with other studies conducted in Poland,[20],[28] a study in the USA,[16],[17] Denmark[19] and Brazil.[23] Although not statistically significant, our study results do show that exposure to pesticides, whether occurring when a mother is not pregnant or during pregnancy increased the likelihood of low birth weight by 80% (95% CI: 0.62, 5.21) and 142% (95% CI: 0.73, 8.08), respectively. Given the study’s relatively small sample size of children with low birth weight, it is not possible to rule out sample size as the reason for the wide 95% CIs and the lack of statistical significance.

This cross-sectional study relied on mothers’ self-reported information for pesticide use exposure. Although there is a possibility of exposure misclassification, we believe that evidence supports that this would be a non-differential misclassification. However, such misclassification can cause loss of statistical power and may be an additional explanation for the lack of statistical significance. Detailed information on the various types of pesticides was solicited, but the responses to these questions were inadequate to allow an evaluation of the impact of exposure to specific pesticides during pregnancy. Only 503 of the 1006 eligible mothers completed the study questionnaire. This non-participation of subjects may have introduced a self-selection bias which could have affected the results of the study. As the sample sizes of mothers exposed to different durations and types of pesticide were not large enough to allow valid analyses, these could not be included in the analysis. Although this study had some methodological limitations, the findings are supportive of future follow-up studies that will evaluate the long-term effects of exposure to pesticides during pregnancy on children’s health outcomes.


  Conclusion Top


In this study, exposure to pesticides was associated with a non-significant increased risk of low birth weight. Future studies using larger sample sizes and longer follow-up periods are indicated in order to clarify the relationship between pesticide exposure during pregnancy and low birth weight in the child.



 
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    Tables

  [Table 1], [Table 2]


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