Teratogenic Dangers: What Pregnant Women in Thailand should Know

Thai mom


Teratogens are agents or factors that damage the prenatal cellular development of a fetus. Common teratogenes such as alcohol and nicotine (Arnett, 2012, p.70-71) are well-established. What is lesser known in the context of Thailand (and similarly developing nations) are teratogenic agents in seafood such as mercury or teratogenic factors such as iodine deficiency. Both pose significant educational problems in later life.

Thai version (PDF): สิ่งที่หญิงไทยมีครรภ์ควรรู้-อันตรายจากสารที่มีผลต่อการเจริญเติบโตของตัวอ่อนหรือทารกในครรภ์

Teratogenic agent Mercury

Many fish in some of Thailand’s favorite seafood dishes such as Tuna, King Mackerel or the White and Red Snapper, contain significant levels of mercury depending on where the fish have been caught. Highly elevated levels of methyl mercury for examples have been found in Prachin Buri province (The Nation, 2013) and in the vinicity of natural gas production facilities in the Gulf of Thailand (Menasveta & Piyatiratitivorakul, 2008). Mercury from industrial output in water turns into methyl mercury (MeHg). Methyl mercury is a neurotoxin and can cross the placenta and blood-brain barrier where it affects the embryonic CNS (Arnett, p.69). Neuronal loss appears predominantly the cerebellum and across the cerebral cortex. Physical postnatal effects can range from severe cerebral palsy to diminished language skills, memory-loss, tunnel-vision and leading to irreversible lifelong loss of intelligence for the child (Trasande et al., 2005, Grandjean et al., 2010). There appears no minimum threshold for the neurotoxin to take effect.

Teratogenic factor malnutrition: Iodine Deficiency

Iodine deficiency is, according to the WHO (WHO, 2007, Hetzel, 2012), globally the most easily preventable cause of brain damage in children. In the most extreme forms iodine deficiency disorder (IDD) causes cretinism and goiter (hypothyroidism), but milder forms of deficiency may pass unnoticed. Virtually all of Thailand’s provinces suffer from mild to severe iodine deficiency (Charoensiriwatana et al., 2008) which can be explained by the fact that Thai cooking uses virtually no salt, but salty fish sauce which contains non-iodinated salt. Biologically iodine deficiency lowers levels of synaptogmin-1 and PSD-95 in the hippocampus, the area of the brain that accommodates learning processes. Synaptogmin-1 is responsible for developing synapses while PSD-95 promotes synapse maturation and regulates synaptic strength and plasticity (Dong et al., 2013).  Iodine remains thus an important micronutriant for the child’s development for many years after birth (Bougma et al., 2013). The nation-wide IQ level of Thai youth dropped from continuously from 91 in 1997 to only 88 in 2009 (Health Information Thailand, 2011) which is predominantly associated with iodine deficiency. It may explain at least partially the low academic performance of Thai youth by international comparison (Pearson, 2013). Even mild iodine deficiency impairs brain function in children (Mitka, 2013).


Iodine deficiency is theoretically easy to address by making it mandatory for manufacturers of fish sauce to use iodized salt. Although the problem has been recognized by the government, a binding legal regulation has not been implemented. No nationwide campaign has been launched to educate expecting mothers or their consulting GPs.  To reduce methyl mercury exposure fishing in the vinicity of industrial estates or gas production platforms should be made illegal while random checks on local fish markets would need to be conducted. Ideal would be to publish a nation-wide map of teratogenic factor prevalence, perhaps online and updated in real-time, to educate the public.


Arnett, J. J. (2012). Human development: A cultural approach. Upper Saddle River, NJ: Pearson Education, Inc.

Bougma, K., Aboud, F., Harding, K., & Marquis, G. (2013). Iodine and mental development of children 5 years old and under: a systematic review and meta-analysis. Nutrients, 5(4), 1384-1416. doi:10.3390/nu5041384

Charoensiriwatana, W., Srijantr, P., Janejai, N., & Hasan, S. (2008). Application of geographic information system in TSH neonatal screening for monitoring of iodine deficiency areas in Thailand. The Southeast Asian Journal Of Tropical Medicine And Public Health, 39(2), 362-367.

Dong, J., Wang, Y., Wang, Y., Wei, W., Min, H., Song, B., & … Chen, J. (2013). Iodine deficiency increases apoptosis and decreases synaptotagmin-1 and PSD-95 in rat hippocampus. Nutritional Neuroscience, 16(3), 135-141. doi:10.1179/1476830512Y.0000000040

Grandjean, P., Satoh, H., Murata, K., & Eto, K. (2010). Adverse effects of methylmercury: environmental health research implications. Environmental Health Perspectives, 118(8), 1137-1145. doi:10.1289/ehp.0901757

Health Information Thailand (2011). Falling IQs Among Thai Children : Time for More Educational Reform. Retrieved from http://www.hiso.or.th/hiso/picture/reportHealth/ThaiHealth2011/eng2011_14.pdf

Hetzel, B. (2012). The development of a global program for the elimination of brain damage due to iodine deficiency. Asia Pacific Journal Of Clinical Nutrition, 21(2), 164.

Menasveta, P., Piyatiratitivorakul, S. (2008) Monitoring of Mercury Concentration in Fish in the Vicinity of Natural Gas Production Platform in the Gulf of Thailand. Retrieved fromhttp://www.conference.ifas.ufl.edu/emecs9/Presentations/Tuesday/Salon%203-4/am/Session%206/0835%20P%20Mebasveta.pdf

Mitka, M. (2013). Even mild iodine deficiency during gestation may impair brain function in children. JAMA: The Journal Of The American Medical Association, 309(23), 2428. doi:10.1001/jama.2013.7239

Pearson. (2013). Index of cognitive skills and educational attainment Retrieved from http://thelearningcurve.pearson.com/index/index-ranking/overall-score-lowest

The Nation. (2013). Unsafe mercury levels found. Retrieved from http://www.nationmultimedia.com/national/Unsafe-mercury-levels-found-30197612.html

Trasande, L., Landrigan, P. J., & Schechter, C. (2005). Public Health and Economic Consequences of Methyl Mercury Toxicity to the Developing Brain. Environmental Health Perspectives, 113(5), 590-596. doi:10.1289/ehp.7743

World Health Organization. (2007). Assessment of iodine deficiency disorders and monitoring their elimination : a guide for programme managers. – 3rd ed. Retrieved from http://whqlibdoc.who.int/publications/2007/9789241595827_eng.pdf

 Postscriptum (below): A little evidence that research has been spot-on

iodine eggs


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