Factors associated with employment status before and during pregnancy: Implications for studies of pregnancy outcomes

Physical job demands in pregnancy and associated musculoskeletal health and employment outcomes: a systematic review

OBJECTIVE

A decline in musculoskeletal health during pregnancy is an underappreciated adverse outcome of pregnancy that can have immediate and long-term health consequences. High physical job demands are known risk factors for nontraumatic musculoskeletal disorders in the general working population. Evidence from meta-analyses suggest that occupational lifting and prolonged standing during pregnancy may increase risk of adverse pregnancy outcomes. This systematic review examined associations between occupational lifting or postural load in pregnancy and associated musculoskeletal disorders and related sequalae.

DATA SOURCES

Five electronic databases (Medline, Embase, CINAHL, NIOSHTIC-2, and Ergonomic Abstracts) were searched from 1990 to July 2022 for studies in any language. A Web of Science snowball search was performed in December 2022. Reference lists were manually reviewed.

STUDY ELIGIBILITY CRITERIA

Eligible studies reported associations between occupational lifting or postural load and musculoskeletal health or sequelae (eg, employment outcomes) among pregnant and postpartum workers.

METHODS

Data were extracted using a customized form to document study and sample characteristics; and details of exposures, outcomes, covariates, and analyses. Investigators independently assessed study quality for 7 risk-of-bias domains and overall utility, with discrepant ratings resolved through discussion. A narrative synthesis was conducted due to heterogeneity.

RESULTS

Sixteen studies (11 cohort studies, 2 nested case-control studies, and 3 cross-sectional studies) from 8 countries were included (N=142,320 pregnant and N=1744 postpartum workers). Limited but consistent evidence with variable quality ratings, ranging from critical concern to high, suggests that pregnant workers exposed to heavy lifting (usually defined as ≥22 lbs or ≥10 kg) may be at increased risk of functionally limiting pelvic girdle pain and antenatal leave. Moreover, reports of dose-response relationships suggest graded risk levels according to lifting frequency, ranging from 21% to 45% for pelvic girdle pain and 58% to 202% for antenatal leave. Limited but consistent evidence also suggests that postural load increases the risk of employment cessation.

CONCLUSION

Limited but consistent evidence suggests that pregnant workers exposed to heavy lifting and postural load are at increased risk of pelvic girdle pain and employment cessation. Job accommodations to reduce exposure levels may promote safe sustainable employment for pregnant workers.

Multiple Job Holding, Job Changes, and Associations with Gestational Diabetes and Pregnancy-Related Hypertension in the National Birth Defects Prevention Study

We used National Birth Defects Prevention Study data to investigate associations between working patterns shortly before and during pregnancy and gestational diabetes and pregnancy-related hypertension. We analyzed working patterns (multiple-job holders, job changers, single-job holders) during the three months before and during pregnancy for 8140 participants who delivered a live-born child without a birth defect. "Multiple-job holders" worked more than one job simultaneously, "job changers" worked more than one job with no overlap, and "single-job holders" (referent) worked one job. We used multivariable logistic regression to estimate associations between working pattern and each outcome, adjusting for maternal age and educational attainment at delivery. We explored effect measure modification by household income, peak weekly working hours, and maternal race/ethnicity. Multiple-job holders had higher odds of gestational diabetes (adjusted odds ratio [aOR]: 1.5; 95% confidence interval [CI]: 1.1-2.1) and pregnancy-related hypertension (aOR: 1.5; 95% CI: 1.0-2.2) compared with single-job holders. Multiple-job holders with a household income of more than 30,000 USD per year, 32-44 peak weekly working hours, and from racial/ethnic minority groups had higher odds of gestational diabetes compared with single-job holders in respective categories. Detailed occupational information is important for studies of occupation and maternal health.

Social determinants of health and vaccine uptake in pregnancy: Disparities in a diverse, predominately foreign-born population

OBJECTIVE

To identify discrepancies in influenza, Tdap, and COVID-19 vaccine uptake and offer rates among pregnant individuals across various social determinants of health including race, ethnicity, foreign-born status, education level, and health insurance coverage, highlighting potential interventions to improve vaccine uptake in pregnancy.

METHODS

An IRB-approved cross-sectional survey was conducted on the postpartum floor of a large urban hospital in South Florida. Between July to September 2021, 359 participants consented and answered questions on their demographics, social background, and influenza, Tdap, and COVID-19 vaccine history.

RESULTS

Most participants identified as White (67.7 %), Hispanic (67.4 %), and foreign-born (68.5 %) with an average age of 29.7 ± 6 years. There was a significant difference in mean vaccine between White (1.3) and Black individuals (0.9, p = 0.002). Mean uptake was significantly higher in foreign-born individuals (1.3) compared to US-born (0.9, p < 0.001). Mean uptake was significantly higher for those with graduate (1.7) and college (1.4) degrees compared to those with a high school degree (1.0) or less than high school (1.0, p < 0.0001).

CONCLUSION

Significant differences in the uptake and offer rates of influenza, Tdap, and COVID-19 vaccines were observed across a variety of social determinants including educational attainment, employment, insurance, and median income of the zip code of primary residence.

Maternal occupational exposure to selected organic and chlorinated solvents and delivery of small-for-gestational age or preterm infants

BACKGROUND

Potential reproductive effects of organic solvent exposure during pregnancy remain unclear. We investigated the association between maternal occupational exposure during pregnancy to six chlorinated solvents, three aromatic solvents, and Stoddard solvent, and delivery of preterm infants or those born small-for-gestational age (SGA).

METHODS

In this case-control study of SGA and preterm birth (PTB) nested within the National Birth Defects Prevention Study (NBDPS) from 1997 to 2011, we analyzed data from 7504 singleton live births without major birth defects and their mothers. Self-reported information on jobs held in the periconceptional period was assessed for solvent exposure. Unconditional logistic regression was used to estimate the association between maternal occupational exposure (any, none) during early pregnancy to organic solvents and PTB and SGA. Linear regression was used to examine changes in mean birthweight potentially associated with maternal occupational solvent exposure.

RESULTS

Maternal occupational exposure to any organic solvents overall was not associated with an increased odds of PTB (adjusted odds ratio [aOR] = 0.94; 95% confidence interval [CI] 0.67-1.33) or SGA (aOR = 0.93; 95% CI 0.65-1.34). Point estimates increased modestly for higher estimated exposure versus lower, but confidence intervals were wide and not statistically significant. Maternal exposure to solvents was not associated with a statistically significant change in term birthweight among infants.

CONCLUSIONS

Occupational exposure to organic solvents at the frequency and intensity levels found in a population-based sample of pregnant workers was not associated with PTB or SGA; however, we cannot rule out any effects among pregnant workers with uncommonly high exposure to organic solvents.

Associations of Prenatal Agricultural Farm Work with Fetal Overgrowth and Pregnancy Complications in State of Arizona Birth Records

OBJECTIVE

The purpose of this study is to examine fetal growth outcomes from agricultural worker households.

METHODS

Using Arizona 2006 to 2013 birth certificates with parental occupation, we identified N = 623,185 live births by agricultural household status. Logistic regression models estimated adjusted odds ratios (aORs) for macrosomia (>4000 g), postterm birth (>41 weeks), low birth weight (<2500 g), preterm birth (<37 weeks), large for GA, small for GA, and 5-minute APGAR (<7).

RESULTS

Newborns of agricultural households (n = 6371) had a higher risk of macrosomia (aOR, 1.15; 95% CI, 1.05-1.26), large for GA (aOR, 1.12; 95% CI, 1.03-1.22), postterm birth (aOR, 1.20; 95% CI, 1.09-1.33), and low 5-minute APGAR (aOR, 1.39; 95% CI, 1.07-1.81), whereas low birth weight (aOR, 0.85; 95% CI, 0.76-0.96) and preterm birth (aOR, 0.82; 95% CI, 0.74-0.92) were inversely related.

CONCLUSIONS

Having an agriculture working parent increased the likelihood of fetal overgrowth and low APGAR.

Association between secondhand smoke exposure in pregnant women and their socioeconomic status and its interaction with age: a cross-sectional study

Background

Existing evidence highlights that exposure to secondhand smoke (SHS) is a risk factor for pregnant women’s health and is possibly affected by individual characteristics. This study aimed to explore the effect of individual socioeconomic status (SES) on SHS exposure among pregnant women in the third trimester and the interaction effect of age.

Methods

A total of 678 nonsmoking pregnant women with a median age of 29.0 years from 14 communities in a medium-sized city were recruited for this survey. Exposure to SHS was defined as the self-reported smoking habit of a spouse/partner. Individual SES characteristics consisted of marital status, educational attainment, employment and per capita monthly income.

Results

There were 238 (35.1%) participants who suffered from SHS exposure. Compared to the pregnant women who were employed, those who were unemployed were more likely to suffer from SHS exposure (OR = 1.572, 95% CI: 1.013–2.441). Participants who had a high school or technical secondary school education were more likely to be exposed to SHS than those with a college education or above (OR = 1.601, 95% CI: 1.029–2.449). Advanced age was a protective factor for participants with a college education or above (OR = 0.939, 95% CI: 0.884–0.997), but age increased the risk of SHS exposure among women who had unstable marriages (OR = 1.256, 95% CI: 1.019–1.549).

Conclusion

Exposure to SHS was very common among pregnant women in the third trimester. Pregnant women with a low SES and an older age should be considered a key population for the implementation of public health interventions.

Tobacco Smoking during Pregnancy: Women's Perception about the Usefulness of Smoking Cessation Interventions

Tobacco consumption during pregnancy is a serious public health problem due to its negative effects on fetal development and on pregnant women's health and well-being. Thus, it is of utmost importance to plan and implement smoking cessation interventions, to prevent the negative impact of this risk factor, namely on children's health and development. This cross-sectional study aimed at exploring the perceptions and beliefs about the usefulness of smoking cessation interventions during pregnancy, in a sample of pregnant Portuguese women. The smoking use by pregnant women, as well as the risk factors associated with tobacco smoking during pregnancy, were also analyzed. The sample included 247 pregnant Portuguese women aged between 18-43-years-old (M = 30.30, SD = 5.02): 42.5% never smoked, 18.3% quit smoking before pregnancy, 19.0% quit smoking after getting pregnant and 20.2% were current smokers. The pregnant Portuguese women who smoked during pregnancy (current smokers or who quit smoking after getting pregnant) were mostly single or divorced, with lower education levels, showed a higher prevalence of clinically significant anxiety symptoms, and perceived smoking cessation interventions during pregnancy as less useful when compared to women who never smoked or quit smoking prior pregnancy. Daily or weekly smoking cessation interventions, implemented by health professionals such as doctors, nurses, or psychologists are the ones perceived as the most useful for pregnant women. These findings provide important clues for the planning of smoking cessation interventions during pregnancy, highlighting the domains that should be carefully monitored by health professionals. Specific strategies should also be used by health professionals to promote smoking cessation considering the demands of pregnancy and postpartum.

Maternal occupational exposure to endocrine-disrupting chemicals and urogenital anomalies in the offspring

STUDY QUESTION

Is there an association between maternal occupational exposure to endocrine-disrupting chemicals (EDCs) early in pregnancy and subgroups of congenital anomalies of kidney and urinary tract (CAKUT), and hypospadias?

SUMMARY ANSWER

Exposure to specific EDCs can increase the risk of CAKUT and no association with hypospadias was observed.

WHAT IS KNOWN ALREADY

Previous studies showed an association between maternal occupational exposure to EDCs and hypospadias. However, little is known about the effect of these chemicals on the development of CAKUT, especially subgroups of urinary tract anomalies.

STUDY DESIGN, SIZE, DURATION

For this case-control study, cases with urogenital anomalies from the European Concerted Action on Congenital Anomalies and Twins Northern Netherlands (Eurocat NNL) registry and non-malformed controls from the Lifelines children cohort (living in the same catchment region as Eurocat NNL) born between 1997 and 2013 were selected. This study included 530 cases with CAKUT, 364 cases with hypospadias, 7 cases with both a urinary tract anomaly and hypospadias and 5602 non-malformed controls. Cases with a genetic or chromosomal anomaly were excluded, and to avoid genetic correlation, we also excluded cases in which a sibling with the same defect was included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Information on maternal occupation held early in pregnancy was collected via self-administered questionnaires. Job titles were translated into occupational exposure to EDCs using a job-exposure matrix (JEM). Adjusted odds ratios (aORs) and 95% CIs were estimated to assess the association between maternal occupational exposure to EDCs (and to specific types of EDCs) and CAKUT and hypospadias.

MAIN RESULTS AND THE ROLE OF CHANCE

For CAKUT and hypospadias, 23.1% and 22.9% of the cases were exposed to EDCs, respectively, whereas 19.8% of the controls were exposed. We found an association between maternal occupational exposure to organic solvents/alkylphenolic compounds and CAKUT (aOR 1.41, 95% CI 1.01-1.97) that became stronger when combinations of urinary tract anomalies co-occurred with other defects (aOR 7.51, 95% CI 2.41-23.43). An association was also observed for exposure to phthalates/benzophenones/parabens/siloxanes and CAKUT (aOR 1.56, 95% CI 1.06-2.29), specifically urinary collecting system anomalies (aOR 1.62, 95% CI 1.03-2.54) and combinations of urinary tract anomalies (aOR 2.90, 95% CI 1.09-7.71). We observed no association between EDC exposure and hypospadias.

LIMITATIONS, REASONS FOR CAUTION

The different study designs of Eurocat NNL and Lifelines could have introduced differential information bias. Also, exposure misclassification could be an issue: it is possible that the actual exposure differed from the exposure estimated by the JEM. In addition, women could also have been exposed to other exposures not included in the analysis, which could have resulted in residual confounding by co-exposures.

WIDER IMPLICATIONS OF THE FINDINGS

Women, their healthcare providers, and their employers need to be aware that occupational exposure to specific EDCs early in pregnancy may be associated with CAKUT in their offspring. An occupational hygienist should be consulted in order to take exposure to those specific EDCs into consideration when risk assessments are carried out at the workplace.

STUDY FUNDING/COMPETING INTEREST(S)

N.S. was paid by the Graduate School of Medical Sciences (MD/PhD programme), University Medical Center Groningen (UMCG), Groningen, the Netherlands. Eurocat Northern Netherlands is funded by the Dutch Ministry of Health, Welfare and Sports. The Lifelines Biobank initiative has been made possible by subsidy from the Dutch Ministry of Health, Welfare and Sport, the Dutch Ministry of Economic Affairs, the University Medical Center Groningen (UMCG the Netherlands), University Groningen and the Northern Provinces of the Netherlands. The authors report no conflict of interest.

TRIAL REGISTRATION NO

N/A.

The importance of socioeconomic position in smoking, cessation and environmental tobacco smoke exposure during pregnancy

Tobacco is still a leading cause of premature death and morbidity. Particular attention has been given to pregnant women due to the scientific evidence on the importance of early life exposures for disease onset later in life. The purpose of this study was to assess smoking prevalence, smoking cessation rate and environmental tobacco smoke (ETS) exposure, and the role of socioeconomic position (SEP) on these behaviors among pregnant women. Cross-sectional data of 619 pregnant women, aged between 18 and 46 years, from Porto Metropolitan Area, Portugal, on current smoking, ETS exposure and SEP indicators was collected, face-to-face, using a questionnaire filled in during a personal interview at the postpartum hospital stay. The smoking prevalence, and ETS exposure among non-smokers before pregnancy was 27.6% and 57.4%, respectively. 4.1% of the participants reported to have stopped smoking before pregnancy, whereas about 41% quitted along pregnancy, resulting in a smoking prevalence at birth of 14.6%. Exposure to ETS also decreased throughout pregnancy to 49.8% at birth. Lower educational level was significantly associated with both higher smoking prevalence and exposure to ETS and lower smoking cessation. This study demonstrates that smoking and ETS exposure during pregnancy remains high, and that there are still significant socioeconomic inequalities in smoking; thus tobacco-focused preventive interventions need to be reinforced.

Differences in pre-pregnancy diet quality by occupation among employed women

OBJECTIVE

Maternal risk factors for pregnancy outcomes are known to vary by employment status. We evaluated whether pre-pregnancy diet quality varies by occupation in a population-based sample.

DESIGN

We analysed interview data from 7341 mothers in a national case-control study of pregnancy outcomes. Self-reported job(s) held during the 3 months before pregnancy were classified using Standard Occupational Classification (SOC) codes. Usual diet in the year before conception was assessed with a semi-quantitative FFQ and evaluated using the Diet Quality Index for Pregnancy (DQI-P). Using logistic regression, we calculated adjusted OR and 95 % CI to estimate associations between low diet quality (defined as the lowest quartile of DQI-P scores) and occupation types.

SETTING

The National Birth Defects Prevention Study: Arkansas, California, Georgia, Iowa, Massachusetts, North Carolina, New Jersey, New York, Texas, Utah.

PARTICIPANTS

Employed mothers of infants born between 1997 and 2011.

RESULTS

No occupation was strongly associated with low diet quality. Moderate but relatively imprecise associations were observed for women employed in management (OR: 1·3; 95 % CI: 1·1, 1·7); arts, design, entertainment, sports and media (OR: 1·4; 95 % CI: 0·9, 2·1); protective service (OR 1·3; 95 % CI: 0·7, 2·5) and farming, fishing, and forestry occupations (OR: 0·5; 95 % CI: 0·2, 1·1).

CONCLUSIONS

Our analyses suggest that women in certain occupations may have lower diet quality in the months before pregnancy. Further research is needed to determine whether certain occupations could benefit from interventions to improve diet quality in the workplace for women of reproductive age.

Maternal occupational exposure to solvents and gastroschisis in offspring - National Birth Defects Prevention Study 1997-2011

Objectives

The aim of this study was to assess the association between maternal occupational exposure to solvents and gastroschisis in offspring.

Methods

We used data from the National Birth Defects Prevention Study, a large population-based case-control study of major birth defects conducted in 10 US states from 1997 to 2011. Infants with gastroschisis were ascertained by active birth defects surveillance systems. Control infants without major birth defects were selected from vital records or birth hospital records. Self-reported maternal occupational histories were collected by telephone interview. Industrial hygienists reviewed this information to estimate exposure to aromatic, chlorinated and petroleum-based solvents from 1 month before conception through the first trimester of pregnancy. Cumulative exposure to solvents was estimated for the same period accounting for estimated exposure intensity and frequency, job duration and hours worked per week. ORs and 95% CIs were estimated to assess the association between exposure to any solvents or solvent classes, and gastroschisis risk.

Results

Among 879 cases and 7817 controls, the overall prevalence of periconceptional solvent exposure was 7.3% and 7.4%, respectively. Exposure to any solvent versus no exposure to solvents was not associated with gastroschisis after adjusting for maternal age (OR 1.00, 95% CI 0.75 to 1.32), nor was an association noted for solvent classes. There was no exposure-response relationship between estimated cumulative solvent exposure and gastroschisis after adjusting for maternal age.

Conclusion

Our study found no association between maternal occupational solvent exposure and gastroschisis in offspring. Further research is needed to understand risk factors for gastroschisis.

Electronic Informed Consent to Facilitate Recruitment of Pregnant Women Into Research

Methods to obtain informed consent digitally or electronically may increase the participation of racially and geographically diverse pregnant women in prospective research, which is essential to improve the evidence base for maternity care. We evaluated the feasibility and utility of e-consent in the first year of a multiyear clinical trial involving pregnant women. Of the 86 women screened, 71 were eligible, 65 (93% of eligible) agreed to review the e-consent form, and 61 (86% of eligible) completed the e-consent process. Of the interested women who were sent the e-consent link, all were able to complete the e-consent process, even those who reported low health literacy. Women of all racial and ethnic groups were equally likely to consent, and the sample of women who consented was consistent with practice demographics. E-consent is feasible and easy to use with pregnant women and may expedite enrollment of a representative sample.

Prevalence and predictors of maternal smoking prior to and during pregnancy in a regional Danish population: a cross-sectional study

BACKGROUND

Maternal smoking is still a major public health problem posing the risk of several negative health outcomes for both the pregnant woman and her offspring. The prevalence of maternal smoking in Denmark and other high-income countries has decreased continuously since the 1980s, and a prevalence below 10% of women who continue to smoke during pregnancy has been reported in studies after 2010. Previous studies have shown that low socioeconomic status is associated with maternal smoking. Information from the Danish Birth Register about maternal smoking shows that the prevalence of women who report to smoke in pregnancy has decreased continuously with 23.3% who reported ever smoking in pregnancy in 2000, 12.9% in 2010 and 9.0% in 2017. The aim of this study was to estimate the prevalence of maternal smoking at the time of conception and at 20 weeks of gestation in a regional Danish population, to describe differences in maternal characteristics among smokers, quitters and never-smokers, and to estimate predictors of smoking at the time of conception.

METHODS

A cross-sectional study was conducted among pregnant women receiving antenatal care at the Department of Obstetrics, Zealand University Hospital, Denmark from August 2015 to March 2016 (n = 566). The main outcome was smoking at the time of conception and at 20 weeks of gestation. The questionnaire also collected information about maternal, health-related and sociodemographic characteristics. Descriptive analysis was conducted, and multivariate logistic regression analysis was used to assess the potential associated predictors (adjusted odds ratio).

RESULTS

The prevalence of self-reported smoking at the time of conception was 16% (n = 90) and 6% smoked at 20 weeks of gestation (n = 35), as 61% of smokers quit smoking during early pregnancy. Multiple logistic regression analysis showed that significant predictors for smoking at conception were the socioeconomic factors; ≤12 years of education, shift work and being unemployed.

CONCLUSION

The prevalence of self-reported maternal smoking in this regional Danish population of pregnant women is lower than seen in previous studies. However, predictors for smoking at the time of conception remain to be factors of low socioeconomic status confirming a social inequality in maternal smoking. Women at risk of smoking during pregnancy must be identified in early pregnancy or even before pregnancy and be offered interventions to help them quit smoking.

Structure and Control of Healthy Worker Effects in Studies of Pregnancy Outcomes

Much of the literature on the healthy worker effect focuses on studies of chronic disease and mortality; however, when studying pregnancy outcomes, these effects might differ because of the short, defined risk periods of most pregnancy outcomes. Three pregnancy-specific healthy worker effects have also been described, but the structure of these effects has not yet been investigated when occupational exposure, and not employment status, is the exposure of interest. We used directed acyclic graphs to examine healthy worker effects in studies of occupational exposures and pregnancy outcomes: the healthy hire effect, the healthy worker survivor effect, the desperation/privilege effect (differential workforce reentry after pregnancy), the reproductively unhealthy worker effect (women with live births leave the workforce, while women with nonlive births do not), and the insecure pregnancy effect (women with adverse pregnancy outcomes reduce their exposures in subsequent pregnancies). Given our assumptions, we conclude that the healthy hire effect, the desperation/privilege effect, the reproductively unhealthy worker effect, and the insecure pregnancy effect result from confounding that can be addressed if data on measured confounders, such as employment status, are available. The presence of the healthy worker survivor effect, however, varies by study design. Different types of healthy worker effects can be present in studies of occupational exposure and pregnancy outcomes, and many of them are easily addressed analytically.

Maternal arsenic exposure and nonsyndromic orofacial clefts

BACKGROUND

Arsenic is widely distributed in the environment in both inorganic and organic forms. Evidence from animal studies suggests that maternal inorganic arsenic may lead to the development of orofacial clefts (OFC)s in offspring. This evidence, together with the limited epidemiologic data available, supports the need for a comprehensive examination of major sources of arsenic exposure and OFCs in humans.

METHODS

Using interview data collected in the National Birth Defects Prevention Study, public and well water arsenic sampling data, and dietary arsenic estimates, we compared expert-rater assessed occupational arsenic exposure, individual-level exposure to arsenic through drinking water, and dietary arsenic exposure between mothers of OFC cases (N = 435) and unaffected controls (N = 1267). Associations for each source of exposure were estimated for cleft lip ± palate (CL/P) and cleft palate (CP) using unconditional logistic regression analyses.

RESULTS

Associations for maternal drinking water arsenic exposure and CL/P were near or below unity, whereas those for dietary arsenic exposure tended to be positive. For CP, positive associations were observed for maternal occupational arsenic and inorganic arsenic exposures, with confidence intervals that excluded the null value, whereas those for drinking water or dietary arsenic exposures tended to be near or below unity.

CONCLUSIONS

Positive associations were observed for maternal occupational arsenic exposure and CP and for maternal dietary arsenic exposure and CL/P; the remainder of associations estimated tended to be near or below unity. Given the exploratory nature of our study, the results should be interpreted cautiously, and continued research using improved exposure assessment methodologies is recommended.

Parental occupational pesticide exposure and nonsyndromic orofacial clefts

Nonsyndromic orofacial clefts are common birth defects. Reported risks for orofacial clefts associated with parental occupational pesticide exposure are mixed. To examine the role of parental pesticide exposure in orofacial cleft development in offspring, this study compared population-based case-control data for parental occupational exposures to insecticides, herbicides, and fungicides, alone or in combinations, during maternal (1 month before through 3 months after conception) and paternal (3 months before through 3 months after conception) critical exposure periods between orofacial cleft cases and unaffected controls. Multivariable logistic regression was used to estimate odds ratios, adjusted for relevant covariables, and 95% confidence intervals for any (yes, no) and cumulative (none, low [<median exposure level in controls], high [≥median exposure level in controls]) occupational pesticide exposures and cleft lip ± cleft palate and cleft palate. Associations for cleft lip ± cleft palate tended to be near unity for maternal or paternal occupational pesticide exposures, except for low paternal exposure to any pesticide, which produced a statistically significant inverse association with this subtype. Associations for cleft palate tended to be near unity for maternal exposures and mostly positive, but non-significant, for paternal exposures; a significant positive association was observed between paternal low exposure to insecticide + herbicide + fungicide and cleft palate. Combined parental exposure produced non-significant associations near or below unity for all orofacial cleft cases combined and cleft lip ± cleft palate and positive, but non-significant, associations for cleft palate. This study observed associations mostly near unity between maternal occupational pesticide exposure and orofacial clefts. Associations for paternal occupational pesticide exposures were mostly near or below unity for cleft lip ± cleft palate, and mostly positive for cleft palate. However, due to the limitations of this study, these subtype-specific results should be interpreted cautiously. Future research examining parental occupational pesticide exposure and orofacial clefts should attempt to improve exposure assessment and increase sample size to better facilitate risk estimation.

Maternal occupational cadmium exposure and nonsyndromic orofacial clefts

BACKGROUND

Cigarette smoking is a well-studied risk factor for orofacial clefts (OFCs). Little is known about which constituents in cigarette smoke contribute to this teratogenicity in humans. One constituent, cadmium, has been associated with OFCs in animal studies; in humans, the role of maternal cadmium exposure on OFCs, independent of cigarette smoke, is unclear. In particular, the relation between maternal occupational cadmium exposure and OFCs is largely unexplored.

METHODS

Using data from a large, population-based case-control study, we compared expert rater assessed maternal occupational cadmium exposure from self-reported occupational histories during the period 1 month before through 3 months after conception between OFC cases (n = 1,185) and unaffected controls (n = 2,832). Multivariable logistic regression analyses were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals for any (yes/no) and cumulative (no, low, high exposure) occupational cadmium exposures and all OFCs, cleft lip ± cleft palate (CL/P) and cleft palate (CP).

RESULTS

Overall, 45 mothers (cases = 13, controls = 32) were rated as having occupational cadmium exposure. Comparing all OFCs to controls, we observed inverse, nonsignificant aORs for any or low exposure, and positive, nonsignificant aORs for high exposure. Where data were available, aORs for CL/P and CP tended to parallel those for all OFCs.

CONCLUSION

To our knowledge, this is the first study to specifically examine maternal occupational cadmium exposure and OFCs, using expert rater exposure assessment. The small numbers of exposed mothers observed, however, led to imprecise estimates. Continued research using more detailed occupational exposure assessment and increased sample sizes is recommended.