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Introduction
Smokeless tobacco use is a growing public health concern, with potential adverse implications for foetal outcomes if consumed during pregnancy. Birth weight is an important predictive measure for health outcomes of a child throughout their lifespan. Despite extensive literature, it is unclear whether smokeless tobacco consumption during pregnancy has an adverse effect on birth weight. Hence, this review was conducted to determine whether an association exists between maternal smokeless tobacco consumption during pregnancy and birth weight of infants.
Methods
Systematic literature search was performed in Medline (via PubMed), Embase, Scopus, and CINAHL with no restrictions on language or time until May 2024. All observational studies that examined the relationship between maternal smokeless tobacco use and low birth weight of infants were eligible for inclusion. Methodological quality of included studies was assessed using the Newcastle Ottawa Scale.
Results
Thirty-three studies were eligible for the review, including twenty-eight cohort, three case-control and two cross-sectional studies. A statistically significant association between use of smokeless tobacco and low birth weight was reported in thirteen studies. Eleven studies reported a statistically significant reduction in mean birth weight in maternal smokeless tobacco users. Pooled estimates of eighteen studies with 733,061 participants showed that there was a statistically significant association (OR = 2.25 [1.63, 3.11] P<0.001); between maternal smokeless tobacco use during pregnancy and low birth weight. Subgroup analysis found a significant association between mishri consumption during pregnancy and low birth weight (n = 646 participants, OR = 10.98 [2.03, 59.34], P = 0.005), but not betel nut (n = 8007 participants, OR = 1.02 [0.84, 1.25]), betel quid (n = 483 participants, OR = 1.51 [0.47, 4.89]) or khat (n = 475 participants, OR = 1.41 [0.64–3.09]).
Conclusions
This review presents an association between maternal smokeless tobacco use and low birth weight, and reduction in mean birth weight. It is suggested that cessation and reduction of maternal smokeless tobacco use should receive specific attention within routine prenatal care.
Implications
The results of this study highlight the need for further preventive public health campaigns to create awareness about detrimental effects of smokeless tobacco on foetal outcomes. Patient education in the primary care setting will aid in promoting smokeless tobacco cessation prior to pregnancy.

引言
无烟烟草使用已成为日益凸显的公共卫生问题，若于妊娠期使用，可能对胎儿结局产生不良影响。出生体重是评估儿童终身健康结局的重要预测指标。尽管已有大量相关研究，但目前仍不明确妊娠期无烟烟草使用是否会对出生体重造成不良影响。因此，本综述旨在探讨妊娠期母亲无烟烟草使用与婴儿出生体重之间是否存在关联。

方法
本研究通过MEDLINE（通过PubMed平台）、Embase、Scopus及CINAHL数据库开展系统文献检索，检索不受语言及发表时间限制，直至2024年5月。纳入所有探讨妊娠期母亲无烟烟草使用与婴儿低出生体重关联的观察性研究。采用纽卡斯尔-渥太华量表（Newcastle Ottawa Scale）对纳入研究的方法学质量进行评估。

结果
本综述共纳入33项符合标准的研究，其中包含28项队列研究、3项病例对照研究与2项横断面研究。13项研究显示无烟烟草使用与低出生体重间存在具有统计学意义的关联。11项研究表明，妊娠期无烟烟草使用者所产婴儿的平均出生体重存在具有统计学意义的降低。对18项共纳入733061名受试者的研究进行合并效应量分析后发现，妊娠期母亲无烟烟草使用与低出生体重间存在显著统计学关联（比值比（OR）=2.25，95%置信区间[1.63, 3.11]，P<0.001）。亚组分析结果显示，妊娠期食用mishri与低出生体重间存在显著关联（n=646名受试者，OR=10.98 [2.03, 59.34]，P=0.005），但未发现槟榔果（n=8007名受试者，OR=1.02 [0.84, 1.25]）、槟榔嚼块（n=483名受试者，OR=1.51 [0.47, 4.89]）或恰特草（n=475名受试者，OR=1.41 [0.64–3.09]）与低出生体重间存在显著关联。

结论
本综述证实妊娠期母亲无烟烟草使用与低出生体重及平均出生体重降低存在关联。建议在常规产前保健中，应重点关注妊娠期女性无烟烟草使用的戒断与减量工作。

研究启示
本研究结果凸显了开展更多预防性公共卫生宣传活动的必要性，以提升公众对无烟烟草损害胎儿健康结局的认知。在基层医疗场景中开展患者教育，将有助于推动育龄女性在孕前戒断无烟烟草使用。