toxics Article Organophosphate Pesticide Exposures in Early and Late Pregnancy Influence Different Aspects of Infant Developmental Performance Boonsita Suwannakul 1 , Ratana Sapbamrer 1,2, *, Natrujee Wiwattanadittakul 3 and Surat Hongsibsong 2,4   Citation: Suwannakul, B.; Sapbamrer, R.; Wiwattanadittakul, N.; Hongsibsong, S. Organophosphate Pesticide Exposures in Early and Late Pregnancy Influence Different Aspects of Infant Developmental Performance. Toxics 2021, 9, 99. https://doi.org/10.3390/toxics 9050099 Academic Editors: Whitney Cowell and Caitlin Howe Received: 2 March 2021 Accepted: 26 April 2021 Published: 30 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Community Medicine, Faculty of Medicine, Chiang Mai University, 110 Inthavaroros, Sri Phum Subdistrict, Muang District, Chiang Mai 50200, Thailand; boonsitasuwannakul@gmail.com 2 Environmental and Occupational Health Sciences and Non Communicable Diseases Center of Excellence, Chiang Mai University, 110 Inthavaroros Road, Sriphum Subdistrict, Muang District, Chiang Mai 50200, Thailand; s_hongsibsong@hotmail.com 3 Department of Pediatrics, Faculty of Medicine, Chiang Mai University, 110 Inthavaroros, Sri Phum Subdistrict, Muang District, Chiang Mai 50200, Thailand; natrujee.w@gmail.com 4 School of Health Science Research, Research Institute for Health Sciences, Chiang Mai University, 110 Inthavaroros, Sri Phum Subdistrict, Muang District, Chiang Mai 50200, Thailand * Correspondence: lekratana56@gmail.com or ratana.sapbamrer@cmu.ac.th; Tel.: +66-053-935-472 Abstract: Organophosphate (OP) pesticides can transfer from mother to fetus via the placenta and amniotic fluid and may affect the development of infants. This study aims to evaluate the associations between maternal OP concentrations collected in the 1st–2nd trimester and the 3rd trimester of pregnancy and the infant developmental performance. The Screening Test of the Bayley Scales of Infants and Toddler Development, Third Edition (BSID–III screening test) was used to assess development performance at 2 and 6 months of age. Multiple regression analysis showed a negative correlation between cognitive performance at 2 months and maternal diethylthiophosphate (DETP) levels in the 1st–2nd trimester ( β ± SE = −0.012 ± 0.004, p < 0.05). We also found that expressive communication and fine motor performance at 6 months were negatively associated with maternal diethyldithiophosphate (DEDTP) levels in the 3rd trimester ( β ± SE = −0.047 ± 0.016, p < 0.05, and β ± SE = −0.044 ± 0.017, p < 0.05, respectively). These results suggest that maternal ethylated OP concentrations at different timing of exposure during pregnancy may influence different aspects of infant developmental performance. Keywords: organophosphates; prenatal exposure; developmental performance; infants; pesticides 1. Introduction Organophosphate (OP) pesticides are a class of insecticide commonly used for agri- cultural purposes to control pests. Chronic low-dose exposure to OP pesticides such as occupational exposure could induce long-term adverse health effects through a non- cholinergic process. Some of these effects could include cytotoxicity, cytoarchitectural abnormalities, neuroinflammation, abnormal energy homeostasis and neurotransmission, and blood–brain barrier impairment [1]. Prenatal exposure to OP pesticides is potentially deleterious to the fetus since these chemicals can be passed to the fetus via the placenta and amniotic fluid [2]. Fetuses and young children are more susceptible to the neurotoxic effects of OP than adults as the human central nervous system, especially the brain, is undergoing rapid growth and development during the fetal period [3]. Fetuses and young children also have lower levels of detoxifying enzymes making the deactivation of OP less effective [4]. It has been shown that accumulation of OP in the placenta may disrupt fetal development. A recent study reported that maternal urinary OP concentrations collected during early and mid–pregnancy were inversely associated with fetal length and weight in mid–pregnancy [5]. Prenatal OP exposure had also been shown to have impact on birth Toxics 2021, 9, 99. https://doi.org/10.3390/toxics9050099 https://www.mdpi.com/journal/toxics