Adverse pregnancy outcomes in relation to water consumption: a re-analysis of data from the original Santa Clara County Study, California, 1980-1981.

Residents of a census tract that received drinking water from a well contaminated with solvents were previously shown to experience a spontaneous abortion rate over twice that occurring in an unexposed census tract. In addition, the rate of birth defects in the exposed tract was three times that in the unexposed tract. Surprisingly, increased tapwater consumption was associated with higher rates of spontaneous abortions in both the exposed and the unexposed tracts. Subsequent studies in this area have investigated the relation between spontaneous abortions and consumption of tapwater in more detail. In this report, data from the original study have been re-analyzed using methods comparable with those used in more recent studies. These results confirm the association between spontaneous abortions and reported cold tapwater consumption that was seen in the original study. The observed effect was not due to maternal risk factors, nor was it a function of consumption of bottled water. After controlling for bottled water, the odds ratio for consumption of tapwater was 3.4 (95% confidence interval = 0.6-19.4).     

Parental cigarette smoking and the risk of spontaneous abortion.

Although cigarette smoking is often considered a risk factor for spontaneous abortion, the epidemiologic literature is actually inconsistent. Therefore, the authors examined maternal and paternal smoking and maternal passive smoke exposure using data from a large case-control study of spontaneous abortion (626 cases and 1,300 controls) conducted in Santa Clara County, California, in 1986 and 1987. No excess risk of spontaneous abortion was seen in the 1% of women who smoked an average of more than 20 cigarettes per day in the first trimester. Moderate smokers (11-20 cigarettes per day) had a slightly elevated crude odds ratio of 1.3 (95% confidence interval 0.9-1.9), which was close to unity after adjustment for covariates. Paternal smoking showed a slight crude elevation for moderate and heavy smoking, but no association after adjustment. In contrast, maternal exposure to environmental tobacco smoke for 1 hour or more per day was associated with spontaneous abortion, even after adjustment (odds ratio = 1.5, 95% confidence interval 1.2-1.9). For both maternal direct and environmental exposure, the association appeared to be stronger in second-trimester abortions. Several studies have found stronger associations of smoking with late versus early abortions, perhaps reflecting smoking-associated placental insufficiency and fetal hypoxia.     

The associations of maternal caffeine consumption and nausea with spontaneous abortion

To examine whether maternal caffeine consumption is associated with the risk of spontaneous abortion, we analyzed data from a population-based prospective study. The study population comprised 575 women delivering singleton livebirths and 75 women who had spontaneous abortions. The subjects were predominantly white, middle-class women enrolled before pregnancy. Study participants were traced to delivery of a liveborn, singleton infant or a spontaneous abortion. Of the 71 women who did not experience nausea, 29.6% had a spontaneous abortion, compared with 7.2% of 514 women who did experience nausea. Maternal caffeine consumption before pregnancy, or in women without nausea, did not increase the risk of spontaneous abortion, whereas maternal caffeine consumption during the first trimester after nausea started might increase risk of spontaneous abortion (risk ratio = 5.4, 95% confidence interval = 2.0-14.6 for caffeine consumption > or = 300 mg per day compared with < 20 mg per day). These results suggest that maternal caffeine consumption during pregnancy may influence fetal viability in women with nausea.     

Gestational vaginal bleeding and pregnancy outcome

The relation between vaginal bleeding and pregnancy outcome was examined in a prospective study of 3,531 women seeking prenatal care in New York City from 1975 through 1985. Women were interviewed in the second trimester or later and were followed up at delivery. The frequency of vaginal bleeding during pregnancy was 22%. Few maternal characteristics or exposures were predictive of bleeding, and those that were associated with an increased risk of bleeding were only marginally so. Risk factors included advanced maternal age, previous spontaneous or induced abortion, working during pregnancy, and certain gynecologic conditions (fibroids, cervical inflammation, and ovarian cysts). Severity of bleeding was examined in relation to birth weight and length of gestation at delivery. Light bleeding during pregnancy was not associated with decreased birth weight or with shortened gestation at delivery. Heavy bleeding was associated with a decrease in mean birth weight of about 100 g (p less than 0.05) but was not significantly associated with the risk of low birth weight (odds ratio (OR) = 1.7, 95% confidence interval (CI) 0.9-3.3). Heavy bleeding was associated with preterm delivery among private patients (OR = 6.4, 95% Cl 1.7-23.5) but not public patients (OR = 0.3, 95% Cl 0.1-1.4). First trimester bleeding of any severity was marginally associated with congenital malformations in the offspring (OR = 1.7, 95% Cl 1.0-2.9); the effect was the same for major and minor abnormalities. There was no association between first trimester bleeding and placental complications of pregnancy or the delivery of a stillborn infant.     

Risk of spontaneous abortion among women exposed to polybrominated biphenyls

Accidental contamination of livestock in Michigan in 1973 with polybrominated biphenyls (PBBs) led to the establishment of a registry of exposed individuals in 1976. At the time of enrollment, serum was collected and analyzed for PBBs and polychlorinated biphenyls (PCBs). In 1997, women aged 18 years or older and active in the registry were invited to participate in a telephone interview about their health. Using generalized estimating equations to account for correlated outcomes within the same woman, we assessed the risk of spontaneous abortion among 529 women with 1344 potentially exposed pregnancies. PBB and PCB exposure were not associated with risk of spontaneous abortion after adjusting for maternal age at conception, age at menarche, and prior infertility. Compared to pregnancies with PBB exposure below the limit of detection, those with levels above 2.9 ppb had a non-significant reduced odds of spontaneous abortion (adjusted OR=0.73; 95% CI=0.47-1.13). Compared to pregnancies with PCB exposure below the limit of detection, those with levels above 6.5 ppb had little difference in risk (adjusted OR=0.91; 95% CI=0.59-1.41). Maternal age at conception above 34 years was significantly associated with elevated risk of spontaneous abortion (OR=2.46; 95% CI=1.10-5.49). The effect of prior infertility was of borderline significance (OR=1.52; 95% CI=0.98-2.38). Older age at menarche was associated with decreased risk of spontaneous abortion (adjusted OR=0.58; 95% CI: 0.38-0.89, comparing menarche at 12-13 with menarche <12). Our results do not support an association between exposure to PBBs or PCBs and risk of spontaneous abortion.     

Are maternal fertility problems related to childhood leukaemia?

An explorative case-control study was conducted in The Netherlands. The cases were obtained from a complete nationwide register of childhood leukaemia (1973-1980). Controls were matched with the cases for year of birth, sex and place of residence. Information about exposures of the mother to potential risk factors in the year before pregnancy and during pregnancy was collected via mailed questionnaires. The analyses concerned data on 519 patients with acute lymphocytic leukaemia and 507 controls. An association between maternal subfertility and childhood leukaemia might be suggested by several findings. A history of two or more miscarriages (OR 1.6; 95% Cl 1.0-2.7) and fertility problems (OR 6.0; 95% Cl 0.9-38.2) were more frequently reported among mothers of cases. The use of oral contraceptives (OC) was significantly higher (OR 1.3; 95% Cl 1.0-1.8) and the duration between discontinuation of OC and the relevant pregnancy was significantly longer. The OR for threatened abortion during the relevant pregnancy was 1.6 (95% Cl 1.0-2.6) and the related use of 'drugs to maintain pregnancy' was 1.9; 95% Cl 1.0-3.5. Among known risk factors, an increased OR for diagnostic irradiation was confirmed (OR 2.2; 95% Cl 1.2-3.8). No association between childhood leukaemia and prenatal viral infections, smoking and alcohol was found.     

Prior spontaneous abortion, prior elective termination, interpregnancy interval, and risk of neural tube defects

A woman with a history of spontaneous abortion in her immediately prior pregnancy may be at increased risk for a pregnancy affected by a neural tube defect (NTD). A short interpregnancy interval may further increase this risk. Using data from a population-based case-control study (1989-1991), the authors investigated NTD risk resulting from a prior spontaneous abortion or elective termination and a short interpregnancy interval. Of 538 interviewed case mothers and 539 interviewed control mothers, 408 case mothers and 433 control mothers reported having a prior pregnancy. Analysis showed a slightly decreased NTD risk among mothers whose immediately prior pregnancy had ended in a spontaneous abortion or elective termination in comparison with a live birth (odds ratio (OR) = 0.82; 95% confidence interval (CI): 0.61, 1.1). This decreased risk was consistent across strata of short or long interpregnancy intervals. Additional analysis revealed an increased NTD risk for mothers with an interpregnancy interval of < or =6 months compared with >12-< or =24 months (OR = 1.5; 95% CI: 0.93, 2.4). This latter risk was greatest among mothers whose immediately prior pregnancy had resulted in a live birth (OR = 2.0; 95% CI: 1.0, 3.8) rather than a spontaneous abortion or elective termination (OR = 0.96; 95% CI: 0.44, 2.1). Adjustment for potential covariates did not substantially alter observed risk estimates.     

Risk of spontaneous abortion in women occupationally exposed to anaesthetic gases: a meta-analysis.

OBJECTIVES: To determine the association between maternal occupational exposure to anaesthetic gases and risk of spontaneous abortion. METHODS: A meta-analysis was performed of published epidemiological studies identified from literature reviews, unsystematic perusal of reference lists of relevant publications, and two Medline searches (1984-92, keywords: anaesthetic gases; anaesthetics; anaesthetics, local; operating rooms; operating room nursing; pregnancy; abortion; 1985-92, keywords: anaesthetics; adverse effects; occupational exposure; anaesthesia, inhalation; operating room nursing; pregnancy; abortion). All peer reviewed studies were retained. Student theses were excluded, as were conference abstracts, unpublished material, and two studies in which data on paternal and maternal occupational exposures were pooled. The relative risk of spontaneous abortion was estimated. RESULTS: One study found no increase in risk of abortion when gases were scavenged or when the exposure to unscavenged gases was low. None of the studies included ambient gas sampling. 24 comparisons between exposed and unexposed women, obtained from 19 reports, were included. The overall relative risk was 1.48 (95% confidence interval (95% CI), 1.4 to 1.58). To test whether this result was influenced by the quality of the studies, the validity of the reviewed papers was rated on the basis of three criteria: appropriateness of the unexposed comparison group, control for non-occupational confounding variables, and response rate. The estimate of risk increased to 1.9 (95% CI, 1.72 to 2.09) when analysis was restricted to the six comparisons which were rated the most rigorous. CONCLUSIONS: Epidemiological studies based on data obtained in the prescavenging era indicate an increased risk of spontaneous abortion. The estimated increased risk was not diminished but rather increased by exclusion of the more methodologically flawed studies.     

Breast cancer in relation to the occurrence and time of induced and spontaneous abortion

The authors evaluated whether an induced or spontaneous abortion during the first six months of gestation, particularly if it occurs before the first term pregnancy, increases the risk of breast cancer. Data from a case-control study of women under 70 years of age were used: 3,200 cases of breast cancer were compared with 4,844 controls with nonmalignant nongynecologic conditions. Among both nulliparous and parous women, the risk of breast cancer was not related to the number of induced or spontaneous abortions. After allowance for all identified potential confounding factors, the estimated relative risk for nulliparous women with an induced abortion relative to those who had never been pregnant was 1.3 (95% confidence interval (CI) 0.8-2.2), and for spontaneous abortion, the corresponding estimate was 0.9 (95% CI 0.5-1.5). Among parous women, the estimated relative risks were 1.2 (95% CI 0.9-1.6) for an induced abortion and 0.9 (95% CI 0.8-1.0) for a spontaneous abortion, relative to never having had an abortion of any type. The time of the abortion had little effect: The relative risk estimates were 0.9 (95% CI 0.5-1.4) for induced abortion before the first term birth, 1.4 (95% CI 1.0-1.9) for induced abortion first occurring after the first term birth, 0.9 (95% CI 0.7-1.2) for spontaneous abortion before the first term birth, and 0.9 (95% CI 0.7-1.0) for spontaneous abortion first occurring after the first term birth. Similar results were evident for women under age 40, among whom the frequency of induced abortion was relatively high. These data suggest that the risk of breast cancer is not materially affected by abortion, regardless of whether it occurs before or after the first term birth.     

Spontaneous abortion and work with visual display units.

OBJECTIVE--To determine whether women who work with visual display units are at increased risk of spontaneous abortion. DESIGN--Case-control study. SETTING--Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area. SUBJECTS--Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care. MAIN OUTCOME MEASURES--Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview. RESULTS--No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions. CONCLUSION--Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.     

Spontaneous abortion and work with visual display units.

OBJECTIVE--To determine whether women who work with visual display units are at increased risk of spontaneous abortion. DESIGN--Case-control study. SETTING--Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area. SUBJECTS--Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care. MAIN OUTCOME MEASURES--Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview. RESULTS--No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions. CONCLUSION--Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.     

妇女生殖道解脲支原体感染与自然流产关联的meta分析

目的:探讨妇女生殖道解脲支原体感染与自然流产、稽留流产发生关联。方法:检索自然流产和稽留流产文献数据并进行整理,用Mantel-Haenszel法合并OR值,并进行meta分析。结果:妇女孕早期生殖道解脲支原体感染发生自然流产的合并OR值为4.72(95%CI:3.77～5.92),发生稽留流产的合并OR值为4.31(95%CI:2.68～6.94);在有解脲支原体感染史妇女中,自然流产和稽留流产的发生危险随着其复发次数的增加而升高。结论:妇女生殖道解脲支原体感染是自然流产和稽留流产发生的可能危险因素,有效诊断解脲支原体感染,可避免妇女生殖道感染中滥用或误用抗生素问题。     

Employment status as a confounder when assessing occupational exposures and spontaneous abortion

Studies of occupational exposure and spontaneous abortion may use pregnancies during which the mother was unemployed as part or all of the unexposed comparison group. Any type of maternal employment, however, may be a risk factor for spontaneous abortion, and potential confounder in occupational reproductive studies. This study evaluates the effect of employment in a cohort of pregnancies of 1535 women. Employed pregnancies had a significantly higher rate of spontaneous abortion (14.5%) than unemployed pregnancies (11.7%) (RR = 1.23, 95% CI = 1.02, 1.49). Gravidity acted as an effect modifier, as the employment effect was seen only in multigravidous pregnancies (RR = 1.38, 95% CI = 1.11, 1.72) and not primigravidous pregnancies (RR = 0.96). The effect persisted when an independent sample of one randomly selected pregnancy per woman was used for the analysis (RR = 1.27, 95% CI = 0.90, 1.79). The data were examined for confounding by other factors which could explain the excess in spontaneous abortion among employed pregnancies. The employment effect persisted with adjustment for other risk factors including maternal age, education, income, maternal diabetes, race, alcohol usage and smoking, and prior pregnancy ending in induced abortion. Stratifying by prior pregnancy loss eliminated the employment effect among those with prior loss (RR = 1.03) but enhanced the effect among those multigravidous without the risk factor (RR = 1.50, 95% CI = 1.15, 1.97). Selection bias, also, was explored as a possible explanation of this employment effect, but could not be substantiated. Assessment of a true exposure effect requires consideration of a potential employment effect either in the design or analysis.     

Risk of spontaneous abortion in Italy, 1978-1995, and the effect of maternal age, gravidity, marital status, and education

This paper describes the trend in the risk of spontaneous abortion in Italy from 1974 to 1995. There was a dramatic decline in the risk after the law that legalized induced abortion was passed in 1978, which implies that probably many induced abortions performed before 1978 were registered as spontaneous abortions. Data for 1991 have been extracted from the Italian national registers of births and abortions and analyzed to investigate the effects of maternal age, gravidity, marital status, and education on the risk of spontaneous abortion. In comparison with women under age 20 years, the risk is found to be increased for women aged 35-39 (odds ratio = 1.45) and women over age 40 (odds ratio = 3.10). The odds ratio is almost 2 for women who have been pregnant two or more times previously. Unmarried women have an increased risk (odds ratio = 1.33), but no important effect of education was observed. There is an important interaction between maternal age and gravidity. The risk of spontaneous abortion is excessively high for young women with high gravidity. It is hypothesized that this could be due to the effect of short intervals between pregnancies.     

生殖道解脲支原体感染与胚胎停育和反复自然流产关联的meta分析

目的:评价早孕妇女生殖道解脲支原体感染与胚胎停育和反复自然流产发生的风险关联性。方法:在全面回顾文献基础上,分别对检索到的胚胎停育和反复自然流产文献进行数据整理,用Mantel-Haenszel法合并OR值,并进行meta分析。结果:meta分析表明,妇女生殖道解脲支原体感染发生胚胎停育的合并OR值为3.62(95%CI:2.80~4.67),发生反复自然流产的合并OR值为5.66(95%CI:4.46~7.18);有有解脲支原体感染史的妇女中,胚胎停育和反复自然流产的发生风险随着其复发次数的增加发生风险逐渐加强。结论:妇女生殖道解脲支原体感染与胚胎停育和反复自然流产之间存在关联,其强度随着复发次数的增加而逐渐加强。有效治疗生殖道解脲支原体感染,对预防育龄妇女不良妊娠结局的再次发生具有重要作用。     

Paternal and Maternal Smoking Habits before Conception and During the First Trimester: Relation to Spontaneous Abortion

PURPOSE: This study examined the association between maternal smoking before and during the first trimester of pregnancy and spontaneous abortion.

METHODS: We have been conducting a hospital-based case-control study on risk factors for spontaneous abortion in the greater Milan area. We collected information from 782 cases of spontaneous abortions and 1543 controls (women who delivered at term healthy infants).

RESULTS: With respect to never smokers, the odds ratio (OR) were 0.7 (95%, confidence interval (CI), 0.5–1.0) for women who quit smoking and 1.3 (95% CI, 1.0–1.6) for those who continued during pregnancy. Women who smoked more than 10 cigarettes/day in the first trimester were at increased risk of miscarriage, with an OR of 1.4 (95% CI, 1.0–2.1). No relationship was evident between the number of cigarettes smoked before conception and the risk of abortion. Likewise, no association emerged between paternal smoking and miscarriage. Moreover, no significant interaction or modification effect was obtained when strata of age and other major characteristics were investigated.

CONCLUSIONS: The risk of abortion associated with cigarette smoking during the first trimester of pregnancy was measurable and noticeable in this population, and accounted for 9% (95% CI, 6–13%) of all cases. The increased risk of spontaneous abortion in women smoking during pregnancy is a further reason to encourage pregnant women to quit.     

浙江省嘉兴地区初孕妇女自然流产状况研究

目的 了解浙江省嘉兴地区初孕妇女自然流产状况及分布特征.方法 资料来源于北京大学生育健康研究所嘉兴地区围产保健监测及自然流产数据.研究对象为嘉兴地区1993-1995年登记的准备结婚及生育并最终怀孕(不包括人工流产、宫外孕及葡萄胎)的初孕妇女14769名.结果 嘉兴地区初孕妇女自然流产率为9.8%(1454/14769,95%CI:9.3～10.3),平均妊娠诊断孕周为(7.6±2.1)周,平均流产孕周为(10.1±3.1)周.早期(≤12周)自然流产率为7.3%(95%CI:6.8～7.7),占总流产的73.7%.流产集中发生在8～13周,占37.7%.经多因素Cox回归分析,生育年龄≥30岁、农民、文化程度高者自然流产率较高.结论 嘉兴地区初孕妇女自然流产率高于国内其他地区;自然流产主要发生在8～13孕周.     

Influence of paternal age on the risk of spontaneous abortion

The frequency of chromosomal anomalies in spermatozoa appears to increase with male age. Because these anomalies play a role in the etiology of spontaneous abortion, an influence of paternal age on risk of spontaneous abortion is plausible but not established. The aim was to characterize this influence in a prospective study among 5,121 California women, who as members of a prepaid health plan were interviewed in 1990 or 1991 when they were less than 13 weeks' pregnant and who were followed until the end of pregnancy. The risk of spontaneous abortion between weeks 6 and 20 of pregnancy was studied using a Cox model adjusted for maternal age. The adjusted hazard ratio of spontaneous abortion associated with paternal age of 35 years or more, compared with less than 35 years, was 1.27 (95% confidence interval: 1.00, 1.61), with no modification by maternal age. Among women aged less than 30 years, the hazard ratio of spontaneous abortion associated with paternal age of 35 years or more was 1.56 for first trimester spontaneous abortion and 0.87 for early second trimester spontaneous abortion (test of interaction, p = 0.25). In conclusion, the risk of spontaneous abortion increased with increasing paternal age, with a suggestion that the association is stronger for first trimester losses.     

Spontaneous abortion and maternal work in greenhouses

BACKGROUND: A positive association between maternal occupational exposure to pesticide and spontaneous abortion has been reported in some studies. Work in greenhouses may imply exposure of pregnant women to pesticides continuously and at elevated level. METHODS: A total of 717 women working in greenhouses provided information on 973 pregnancies, including 110 spontaneous abortions. These pregnancies were classified as exposed or not exposed according to maternal occupation, re-entry activities and application of pesticides in greenhouses during at least 1 month in the first trimester of pregnancy. The ORs for spontaneous abortion were estimated through a generalised estimate equations model for all orders of pregnancy together, and through a logistic regression model limited to first pregnancies. RESULTS: Increased risks of spontaneous abortion were found for maternal re-entry activities within 24 hr after pesticides were applied (all orders of pregnancy: OR 3.2, 95% CI 1.3-7.7; first pregnancies: OR 3.8, 95% CI 1.0-13.9) and for those who applied pesticides (all orders of pregnancy: OR 2.6, 95% CI 1.0-6.6; first pregnancies: OR 3.7, 95% CI 0.7-20,6) CONCLUSIONS: The observed results support the hypothesis of an association between maternal work in greenhouses and spontaneous abortion. The main limitations of the study are lack of information on the specific chemicals used and the small number of pregnancies heavily exposed to pesticides.     

Interactive Effects of Maternal Vitamin D Status and Socio-Economic Status on the Risk of Spontaneous Abortion: Evidence from Henan Province,China

Background: Maternal vitamin D deficiency might generate adverse reproductive outcomes, and socio-economic inequalities in micronutrient-related diseases have often been found. This study aimed to explore the interactive effects of maternal vitamin D status and socio-economic status (SES) on risk of spontaneous abortion. Methods: A population-based case–control study was conducted including 293 women with spontaneous abortion and 498 control women in December 2009 and January, 2010 in Henan Province, China. Information on pregnancy outcomes, maternal demographic, lifestyle and exposure factors and blood samples were collected at the same time. Vitamin D deficiency was defined as 25(OH)D < 20 ng/mL. SES index was constructed with principal component analysis by aggregating women’s and their husbands’ education level and occupation, and household income and expenditure. Interactive effects were assessed on a multiplicative scale with ratio of the odds ratio (ROR). Results: Compared to those with high SES and vitamin D sufficiency, women with vitamin D deficiency and low SES index had an increased risk of spontaneous abortion (aOR: 1.99; 95% CI: 1.23–3.23). The ROR was 2.06 (95% CI: 1.04–4.10), indicating a significant positive multiplicative interaction. Conclusions: Maternal low SES may strengthen the effect of vitamin D deficiency exposure on spontaneous abortion risk in this Chinese population.