Thulstrup Ane Marie and Bonde Jens Peter
Five specific birth defects were identified:
- Neural tube defects
- Cleft lip and cleft palate
- Congenital heart defects
- Urinary tract defects
- Limb defects
Birth defects or congenital malformations (at time of birth): 3,5% of all live births.
Data on spontaneous abortion may be important for the detection of teratogenic factors.
In nearly 70% of all birth defects, there is still no known risk factor.
Close to 30% of all pregnancies end in a foetal loss or spontaneous abortion.
Neural tube defects
Prevalence in Europe +/- 1 per 1000 births
Protective factor: Folic acid intake
Non-occupational risk factor: hight vitamin A (retinol) intake
Occupational risk: 10 studies (2 cohort & 8 case-control studies)
Possible risks among women working in health care, agriculture and cleaning.
Risk seems to be following exposure to glycol ethers or lead
Caution: Limited evidence !!!
Holmberg et al. / Ericson et al. / Matte et al. / Bianchi et al. / Cordier et al. / Blatter et al. / Lin et al. / Irgens et al. / Blaasaas et al. / Brender et al.
Cleft lip and Cleft palate
Prevalence in Europe:
+/- 1.5 per 1000 births for cleft lip
+/- 0.8 per 1000 births for cleft palate
Well accepted that genetic factors contribute to the aetiology
Protective factor: folic acid intake
Non-occupational risk factors: Maternal smoking - High vitamin A intake
Occupational risk: 11 studies (2 registry-based & 9 case-control studies)
Employment during pregnancy in the leather industry or as a hairdresser has been suggested to be associated with increased risk of cleft lip or cleft palate.
Exposures like organic solvents, glycol ethers and pesticides have been suggested in a number of studies.
Caution: Limited evidence !!!
Holmberg et al. / Matte et al. / Nurminen / Bianchi et al. / Cordier et al. / Lin et al. / Lorente et al. / Blaasaas et al. / Shaw et al. / Carmichael et al. / Chia et al.
Prevalence is +/- 4-6 per 1000 births
Prevalence increased simultaneously with the increasing survival of premature infants.
Possible non-occupational risk factors: alcohol consumption during first trimester, maternal diabetes mellitus, high body mass index & use of antiepileptics
Occupational risk: 7 studies (2 registry-based & 5 case-control studies)
Evidence is inconclusive !!!
Tikkanen et al. / Matte et al. / Bianchi et al. / Cordier et al. / Cedergren et al. / Carmichael et al. / Chia et al.
Prevalence of hypospadias: 2-4 per 1000 births
Prevalence of cryptorchidism: <>
Genetic defects play a role in hypospadias
Occupational risk factors: 8 case-control studies
Few studies do not allow any conclusions on occupational risk for cryptorchidism or for hypospadias !!!
Bianchi et al. / Cordier et al. / Garcia / Matte et al. /Weidner et al. / Vrijheid et al. / Pierik et al.
Prevalence: +/- 0.5-1% per 1000 births
Genetic interaction of teratogenic effects of smoking ?
Non-occupational risk factors: Maternal smoking
Occupational risk: 6 studies
Limited number of studies focusing on limb defects are insufficient to assess the risk !!!
Bianchi et al. / Cordier et al. / Garcia / Matte et al. / Weidner et al. / Vrijheid et al. / Pierik et al.
Discussion & Remarks:
Original literature does not provide clear evidence for causal associations between maternal occupational exposures and specific birth defects.
It seems that little progress has been made since Sever published a review (1994).
There is a strong interaction between age, lifestyle factors (smoking, alcohol, social class, nutrition) and occupational exposures during pregnancy, which complicates the proper interpretation of associations.
Epidemiological research has not convincingly demonstrated any workplace exposure as a specific teratogen but sevral concerns implying possible teratogenic effects of volatile organic solvents, glycol ethers, some pesticides and some heavy metals call for additional research.
It seems to be difficult or impossible to establish exposure-response relationships. Such studies will probably require very large source populations and call for international research cooperation.