BACKGROUND Chlorination is globally used to produce of safe drinking water. Chlorination by-products are easily formed, and there are indications that these are associated with adverse reproductive outcomes. OBJECTIVES We conducted a nationwide register-based prospective study to assess whether gestational exposure to the four most common chlorination by-products [total trihalomethanes (TTHMs)] via tap water was associated with risk of small for gestational age (SGA), preterm delivery, and very preterm delivery. To date, this is one of the largest studies assessing drinking water TTHM-associated adverse reproductive outcomes. METHODS We included all singleton births 2005-2015 (live and stillbirths) of mothers residing in Swedish localities having >10,000 inhabitants, ≤2 operating waterworks, adequate information on chlorination treatment, and a sufficient number of routine TTHM measurements in tap water. Individual maternal second and third trimester exposure was obtained by linking TTHM measurements to residential history, categorized into no chlorination, <5, 5-15, and >15μg TTHM/L. Outcomes and covariates were obtained via the linkage to Swedish health and administrative registers. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by logistic regression using inverse probability weighting. We stratified the analyses by chlorination treatment (chloramine, hypochlorite). RESULTS Based on approximately 500,000 births, we observed a TTHM dose-dependent association with increased risk of SGA, confined to treatment with hypochlorite, corresponding to a multivariable-adjusted OR=1.20 (95% CI: 1.08, 1.33) comparing drinking water TTHM >15μg to the unexposed. Similar results were obtained when, instead of unexposed, the lowest exposure category (<5μg/L TTHM) was used as reference. No clear associations were observed for preterm delivery and very preterm delivery. DISCUSSION Chlorination by-products exposure via drinking water was associated with increased risk of SGA in areas with hypochlorite treatment. https://doi.org/10.1289/EHP6012.

中文翻译：

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饮用水氯化副产物和胎儿生长与早产的暴露：一项基于全国登记的前瞻性研究。

背景技术氯化法在全球范围内被用于生产安全的饮用水。氯化副产物很容易形成，有迹象表明这些副产物与不利的生殖结果有关。目标我们进行了一项基于全国登记册的前瞻性研究，以评估妊娠期通过自来水接触四种最常见的氯化副产物[总三卤甲烷（TTHM）]与小胎龄（SGA），早产，和早产。迄今为止，这是评估饮用水中TTHM相关不良生殖结局的最大研究之一。方法我们纳入了2005-2015年居住在瑞典地区的所有单胎婴儿（活产和死产），这些产妇居住在瑞典的居民人数> 10,000，经营的供水系统≤2，加氯处理的足够信息，以及自来水中足够数量的常规TTHM测量。通过将TTHM测量值与居住史联系起来，获得单独的孕中期和孕晚期暴露，分类为无氯化，<5、5-15和>15μgTTHM / L。结果和协变量是通过与瑞典卫生和行政登记系统的链接获得的。使用逆概率加权通过逻辑回归估算赔率（OR）和95％置信区间（CI）。我们通过氯化处理（氯胺，次氯酸盐）对分析进行了分层。结果基于大约500,000例婴儿，我们观察到TTHM剂量依赖性与SGA风险增加相关，仅限于用次氯酸盐治疗，对应于多变量校正后的OR = 1.20（95％CI：1.08，1.33），比较饮用水TTHM> 15μg至未暴露。当使用最低暴露类别（<5μg/ L TTHM）作为参考时，获得了相似的结果。没有观察到早产和非常早产的明确关联。讨论在次氯酸盐治疗的地区，通过饮用水接触氯化副产物与SGA风险增加有关。https://doi.org/10.1289/EHP6012。