Association Between Maternal Fluoride Level and Preterm Delivery and Low Birth Weight Among Pregnancy at Endemic Fluoride Areas in Lamphun, Thailand : A Pregnancy- Birth Cohort Study

Abstract

BACKGROUND: Many studies mention that fluoride can transfer through placenta and exposure to fluoride during pregnancy can risk to preterm delivery and low birth weight (LBW). Nowadays, water fluoride (WF) at 0.7 mg/L was recommended as standard level for good oral health to protect dental caries while controlling the risk of dental fluorosis. Lamphun is one of six provinces in Thailand where natural WF >10.0 mg/L were found, and >50% of households used water with high fluoride. However, the evidence advocate maternal fluoride level is associated with Preterm delivery and LBW have yet to be well studied in Thailand. This study aims to assess the association between maternal fluoride (MF) among pregnancy with preterm delivery and LBW. To compare the incidence (Relative Risk: RR) of preterm birth and LBW between Low-exposed and Exposed METHODS: the cohort study on pregnancy-birth was conducted in Lamphun province between July 2016 to November 2017.Purpose sampling was used to select study areas of districts with WF >10.0 mg/L in the Mueang Lamphun, Pasang, and Ban Thi districts where WF >10.0 mg/L and LBW >7%. Village WF was used to classify study population group; WF? 0.70 ma/L as Low-exposed and WF>0.70 mg/L as Exposed. The 141-pregnant women age between 20 - 35 years, live in study areas within one year or more, have no risk at first ANC visit, gestational age < 30wks at first coming to the research and plan delivery at Lamphun, Pasang or Ban Thi hospital. Data will collect by interview questionnaires and medical records. Maternal urine at <30wks, 31-33wks, 34-36wks were collected to analyze fluoride level with Ion Selective Electrode (ISE) follow by TISAB. Preterm delivery and LBW were diagnosed by obstetrician or doctors. The descriptive statistics were used to describe general information of pregnant and newborn. Logistic regression will use to test the association between concentration level of fluoride in urine and preterm delivery LBW, and to compare the incidence of preterm delivery and LBW between the two study areas. RESULTS: The average level of maternal urine fluoride (MUF) was 1.27 (? .1.08) mg/L. There was a strong significant difference of MUF (p=.001) between two groups, the MUF level of Exposed (1.65 ? 1.35) was higher than Low-exposed (0.98 ? .0.16). There were not suspected factors statistically significantly associated with Preterm delivery, whereas pregnant who have MUF level more than 0.5 mg/L (p = .003), was associated with increased of LBW. The RR of preterm delivery = 0.35 (95% CI = 0.0748 - 1.7129), and RR of LBW = 1.53 (95% CI = 0.6188 - 3.8011) CONCLUSIONS: Our finding on MUF more than 0.5 mg/L was determined to increase of LBW but there was no associated with Preterm birth.