Early pregnancy blood lead and spontaneous abortion

Although evidence tends to suggest that high levels of lead exposure increase the risk of spontaneous abortion, we do not yet know whether moderate- to low-level exposure elevates risk. Among 351 women (aged 16 to 35 years, with single pregnancies) who were registered for a longitudinal study, 15 (4.3%) women experienced spontaneous abortion after the 12th week of gestation and before the 20th week. We collected participants' blood samples during the first trimester of pregnancy (8-12 weeks) for lead measurement by inductively coupled plasma-mass spectrometry. Mean ± standard deviation of blood lead was 3.8 ± 2.0 μg/dl (range 1.0-20.5 μg/dl) with a geometric mean of 3.5 μg/dl. Mean blood lead concentrations did not differ significantly between spontaneous abortion cases and ongoing pregnancies (3.51 ± 1.42 and 3.83 ± 1.99 μg/dl, respectively). The findings suggest that in apparently healthy women, low blood lead levels (mean < 5 μg/dl) measured in early pregnancy may not be a risk factor for spontaneous abortion.     

The Port Pirie cohort study: maternal blood lead and pregnancy outcome.

During a three-year period, 831 pregnant women in and around Port Pirie, South Australia--a lead smelter community with longstanding lead pollution--were enrolled in a cohort study to examine prospectively the relation between body lead burden and pregnancy outcome. Three-quarters of the enrolled women were residents of the Port Pirie municipality; the other women lived in adjacent towns and countryside. At 14-20 weeks' gestation, the Port Pirie resident women had a mean blood lead concentration of 10.6 micrograms/dl, while the mean in the other (non-Port Pirie) women was 7.6 micrograms/dl. Similar differences were observed in maternal blood samples taken at 30-36 weeks, at delivery, and from the umbilical cord. These blood lead measures, in conjunction with information collected on other risk factors, were then examined in relation to pregnancy outcome. Among 749 pregnancies followed to completion, pre-term delivery was statistically significantly associated, in a dose-response manner, with maternal blood lead concentration at delivery. Mothers of late fetal deaths (stillbirths) had blood lead concentrations at 14-20 weeks' gestation similar to those of all the other women but had lower concentrations at delivery than the other women. Outcomes of pregnancy for which no association with blood lead was detected were spontaneous abortion, low birthweight (for births at term), intrauterine growth retardation, premature rupture of the membranes, and congenital anomalies.     

274例孕妇血铅水平及相关因素的探讨

目的:了解武汉市孕妇血铅水平及其影响因素。方法:将274例来院产检的孕妇分为早、中和晚孕3组进行问卷调查,并采用原子吸收光谱仪测定血铅值。结果:孕妇高铅血症发生率12.77%,孕期血铅呈动态变化,孕早、中和晚期分别为(62.25±20.29)μg/dl、(63.16±24.42)μg/dl和(67.19±26.85)μg/dl,差异有统计学意义(P<0.01)。孕妇血铅值高低与常吃膨化食品、使用化妆品、被动吸烟频数和食用乳制品、钙锌铁剂频数有关。多因素逐步回归分析筛选影响血铅值的因素是孕周、常吃膨化食品、被动吸烟。结论:现阶段武汉城区孕妇血铅水平处于可接受范围;健康教育、环境治理、调整膳食及养成良好的生活行为习惯是减少孕妇铅中毒的有效途径。     

北京市孕妇缺铁性贫血的研究

本文通过对100名妊娠早期孕妇的追踪观察发现,孕妇妊娠中、晚期的铁营养状况普遍较差,血红蛋白、红细胞计数、血浆铁蛋白的平均值均明显低于未婚女青年;红细胞游离原卟啉明显高于未婚青年;妊娠晚期的血浆铁水平和运铁蛋白饱和度较妊娠中期明显下降,红细胞游离原卟啉明显升高。膳食调查的结果表明,妊娠早、中、晚期的营养素多摄入不足,唯铁、维生素C、维生素B_1达到供给量标准。本文结合上述资料从孕前铁营养状况、孕期膳食构成和机体铁状况的动态变化等角度重点讨论了北京城区孕妇贫血的性质和原因,并提出了相应的对策。     

Blood Lead Concentrations and Pregnancy Outcomes

In this study, the authors related blood lead concentrations to Apgar scores, birth weight, gestational age, small-for-gestational age, and hypertension in pregnancy (HIP)/toxemia. Data and blood were collected 4 times during pregnancy from 705 women, aged 12–34 yr. Blood lead concentrations, measured by atomic absorption spectrophotometry, were related to reproductive outcomes, abstracted from medical records. Average blood lead concentrations were 1.2 μg/dl (standard error = ± 0.03). Maternal blood lead concentrations were related significantly to HIP/toxemia—before and after adjusting for age, calcium intake, and race/ethnicity (p < .03). Longitudinal regression analyses revealed that blood lead concentrations in women with HIP/toxemia changed by 0.02 μg/dl for every 0.01 μg/dl change in women without HIP/toxemia. Maternal blood lead concentration and its change were not significantly associated with other reproductive outcomes. Low levels of maternal blood lead concentrations were significantly associated with HIP/toxemia.     

Lead exposure in stained glass workers

To evaluate lead exposure in stained glass workers, we measured blood lead levels in 12 professional glass workers, in 5 hobbyists, and in 4 workers' family members. Professional workers lead levels (mean 20.7 μg/dl) were higher than hobbyists' (11.6 μg/dl) (P = 0.02) or family members' (11.3 μg/dl). Levels increased with years worked, hours worked per week, and percentage of work involving lead. The mean lead concentration in settled dust samples from a stained glass workshop was 11,000 parts per million. Stained glass workers are at increased risk of lead exposure.     

Past pregnancy outcomes among women living in the vicinity of a lead smelter in Kosovo, Yugoslavia.

This analysis compares the rates of spontaneous abortion among women living in the vicinity of a lead smelter with those of women living in a town where blood lead levels were low. Data derive from the obstetric histories of both groups of women obtained while seeking prenatal care for a later pregnancy. A total of 639 women (304 exposed, 335 unexposed) had at least one previous pregnancy and lived at the same address since their first pregnancy. The geometric mean blood lead concentrations in the sample at the time of the interviews were 0.77 mumol/L in the exposed town and 0.25 mumol/L in the unexposed town. The rates of spontaneous abortions in first pregnancies were similar, with 16.4 percent of women in the exposed town and 14.0 percent in the unexposed town reporting loss. The adjusted odds ratio relating town of residence to spontaneous abortion was 1.1 (95% CI = 0.9, 1.4). This analysis represents the first systematic attempt to seek an association between environmental lead exposure and spontaneous abortion. As such, the failure to find a positive association strongly suggests that at the levels of exposure represented in our sample, such an association does not exist.     

Blood lead levels measured prospectively and risk of spontaneous abortion.

Studies of low to moderate level lead exposures have reported mixed findings regarding the risk of spontaneous abortion, despite lead's abortifacient properties at very high doses. To evaluate the risk of spontaneous abortion from low or moderate lead exposures, a nested case-control study was conducted within a cohort of pregnant women in Mexico City, 1994-1996. During their first trimester, 668 women enrolled, were interviewed, and contributed blood specimens. Pregnancies were followed by home visits or telephone calls. Spontaneous abortions before week 21 (n = 35) were matched with pregnancies that survived beyond week 20 (n = 60) on maternal age, hospital, date of enrollment, and gestational age at enrollment. Mean blood lead levels were 12.03 microg/dL for cases and 10.09 microg/dL for controls (p = 0.02). Odds ratios for spontaneous abortion comparing 5-9, 10-14, and > or =15 microg/dL with the referent category of <5 microg/dL of blood lead were 2.3, 5.4, and 12.2, respectively, demonstrating a significant trend (p = 0.03). After multivariate adjustment, the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1, 3.1) for every 5 microg/dL increase in blood lead. Low to moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to US general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations.     

Season Modifies the Relationship between Bone and Blood Lead Levels: The Normative Aging Study

Bone serves as a repository for 75% and 90–95% of lead in children and adults, respectively. Bone lead mobilization heightens during times of increased bone turnover, such as pregnancy, lactation, hyperthyroidism, and the rapid growth of childhood. Blood lead levels show seasonal periodicity. Children demonstrate peak blood lead levels in midsummer and a secondary peak in late winter. Pregnant women demonstrate the highest mean blood lead levels in winter (January-March) and the lowest in summer (July-September). This fluctuation in blood lead levels may be related to seasonal patterns of environmental exposures, but it may also be partially related to the increased mobilization of bone lead stores during the winter months. We performed bone lead measurements using a K-x-ray fluorescent instrument to determine micrograms of lead per gram of bone mineral (parts per million) in middle-aged and elderly men who participated in the Normative Aging Study. We obtained measurements of blood and bone lead during the high sun exposure months of May-August (summer; n = 290); the intermediate sun exposure months of March, April, September, and October (spring/fall; n = 283); and the low sun exposure months of November-February (winter; n = 191). Mean blood lead concentrations were 5.8 μg/dl, 6.1 μg/dl, and 6.6 μg/dl for the summer, spring/fall, and winter, respectively. Mean patella (trabecular bone) lead concentrations were 34.3 μg/gm, 29.7 μ/gm, and 29.0 μg/gm for the summer, spring/fall, and winter time periods, respectively. In multivariate regression models, adjusted for age, smoking, alcohol ingestion, and dietary intake of iron and vitamin C, the authors found a strong interaction between season and bone lead level—with bone lead levels exerting an almost 2-fold greater influence on blood levels during the winter months than the summer months. The authors concluded that elevated blood lead levels in winter may be related to increased mobilization of endogenous bone lead stores, potentially from decreased exposure to sunlight, lower levels of activated vitamin D, and enhanced bone resorption.     

Low-Level Lead Exposure and Blood Lead Levels in Children: A Cross-Sectional Survey

The authors studied 53 girls (44.5%) and 66 (55.5%) boys in Karachi, Pakistan, to determine their blood lead levels. The association between blood lead levels/water lead levels and the possible risk factors and symptoms associated with lead toxicity was explored. The mean lead level for the entire group was 7.9 μg/dl (standard deviation = 4.5 μg/dl). Thirty (25.2%) of the children had lead levels that exceeded 10 μg/dl; 12 (10.0%) of these had lead levels that exceeded 15 μg/dl. Thirteen (20.9%) of the children under the age of 6 yr (n = 62) had lead levels greater than 10 μg/dl, and 6 (9.6%) had levels in excess of 15 μg/dl. The authors found no association (p > .05) between high lead levels in water and blood lead levels in children. Mean blood lead levels were highest in the group of children exposed to various risk factors for lead absorption (e.g., exposure to paint, remodeling, and renovation; use of lead utensils; pica). There was a significant association between a history of exposure to paint/renovation activities and a history of pica. High blood lead levels in the children in Karachi stress the urgency for actions that control lead pollution. Screening programs should be instituted by the state. Individuals must become aware of lead's toxicity, and they must avoid substances that contain lead.     

Paternal Occupational Lead Exposure and Pregnancy Outcome

Abstract

Self-reported reproductive histories of male employees of a lead-zinc smelter were related to pre-conception measures of lead exposure to examine associations between paternal occupational lead exposure and adverse pregnancy outcome The participants reported 2,021 pregnancies which resulted in 1,684 normal live births, 12 stillbirths, 30, birth defects, 203 spontaneous abortions, and 92 “other” outcomes. Birth defects and stillbirths were combined for the analysis. The risk of a stillbirth or birth defect was elevated for pre-conception employment in a high-lead-exposure compared with a low-lead exposure job (odds ratio = 2.7, 95,% confidence interval = 0.7, 9.6). A similar risk was found for pre-conception blood lead levels of 25–39 μg/dL and ≥40μg/dL when compared With blood lead)level of <25μg/dL(OR = 2.9,95% CI = 0.6, 13.3 and OR = 2.5,95% CI = 0.5,11.6, respecdvely). No association was found between pre-conception lead exposure and spontaneous abortion. A relatively low response rate to the questiollnaire and potentially erroneous reporting of reproductive outcome by male workers are limitations of the study.     

The Physiological Response of Animals to β-Nitronaphthalene

The effect of lead exposure on blood pressure in the modern industrial setting is controversial. In this study, we followed 67 workers in a lead-battery plant for 6–10 y, and blood pressure and blood lead levels were measured every 6 mo. Weight, height, alcohol intake, cigarette smoking, and age were recorded. Partial correlation coefficients showed that initial systolic blood pressure, age, and body mass index (i.e., weight/height squared) accounted for 25%, 30.9%, and 20.2%, respectively, of the variance in systolic blood pressure (p < .001 in all cases). Conversely, average blood lead levels (13 ± 3 tests/worker) accounted for only 0.4% of the variance (not significant). Repeated-measures analysis of variance showed a small—but significant—association between blood lead levels and systolic blood pressure. There was a negative correlation between blood lead levels and diastolic blood pressure. There were 18 men with average blood lead levels that were less than 30 μg/dl (average = 25 ± 3 μg/dl), and 32 men had levels of 40 μg/dl or more (average = 47 ± 6 μg/dl). The mean final systolic blood pressure, adjusted for age, and initial systolic blood pressure were 117 ± 13 mm Hg and 114 ± 11 mm Hg, respectively. We concluded that blood lead levels had no clinically significant effect on blood pressure in lead-battery workers. The main predictors of the follow-up systolic blood pressure were age, body mass index, and initial systolic blood-pressure measurements.     

Exposure sources and reasons for testing among women with low blood lead levels

Previous research has focused on highly elevated blood lead (PbB). This study examined reasons for testing and potential sources of exposure among women with PbBs less than 0.72 μmol/l (15 μg/dl). A questionnaire was mailed to 18- to 49-year-old women in upstate New York, USA, who were PbB tested in 2007. The most common testing reason was pregnancy among 125 women who returned the questionnaire. Among women tested for PbB during pregnancy, doctors ordered approximately 80% of tests regardless of lead level. Few women with PbBs less than 0.24 μmol/l (5 μg/dl) reported a potential source of lead exposure. However, among women with PbBs of 0.24-0.71 μmol/L (5-14.9 μg/dl), 29.2% had a job and 21.2% had a hobby with potential lead exposure. There are systematic differences in reasons for testing and exposure sources among women with PbBs less than 0.72 μmol/l and these differences have implications for screening.     

Weight gain and maturity in fetuses exposed to low levels of lead

The relationship between prenatal low-level lead exposure and fetal growth was evaluated in a sample of 4354 pregnancies in which the mean umbilical cord blood lead level was 7.0 micrograms/dl (SD = 3.3; 10th percentile, 3.4 micrograms/dl, 90th percentile, 10.9 micrograms/dl). Higher cord blood lead levels were significantly associated with gestations of slightly longer duration. Comparing infants with cord blood lead levels greater than or equal to 15 micrograms/dl to those with levels less than 5 micrograms/dl, adjusted risk ratios of 1.5 to 2.5 were observed for low birth weight (less than 2500 g) and for fetal growth indices that express birth weight as a function of length of gestation (e.g., small-for-gestational age, intrauterine growth retardation). The 95% confidence intervals of these risk ratios included 1, however, precluding rejection of the null hypothesis of no association. We conclude that the risk of adverse fetal growth is not increased at cord blood lead levels less than 15 micrograms/dl but that modest increases in risk may be associated with levels greater than or equal to 15 micrograms/dl.     

Shift work, nitrous oxide exposure, and spontaneous abortion among Swedish midwives.

OBJECTIVES: To study the relation between irregular work hours, nitrous oxide (N2O) exposure, and the risk of spontaneous abortion. METHODS: All 3985 female members of the Swedish Midwives Association in 1989, born in 1940 or later, received a questionnaire on exposure before and during all of their pregnancies. Questions on work conditions covered occupation, extent of employment, workplace, work schedules, use of anaesthetics, and work load. The association between exposure variables and spontaneous abortion was analysed by logistic regression models. RESULTS: Night work and three shift schedules among midwives showed increased odds ratios (ORs) (95% confidence intervals (95% CI)) 1.63 (0.95-2.81) and 1.49 (0.86-2.59), respectively. The ORs of late spontaneous abortions (after the 12th week of pregnancy) was increased for night work 3.33 (1.13-9.87). Use of N2O (> 50% of the deliveries) was not associated with increased risk of spontaneous abortion OR 0.95 (0.62-1.47). Frequent or permanent shortage of staff was related to an increased risk of spontaneous abortions before the 13th week of pregnancy. CONCLUSIONS: The results support the hypothesis that night work and high work load increase the risk of spontaneous abortion.     

Blood Lead Survey of Children,Pregnant Women,Professional Drivers,Street Workers,and Office Workers in Trujillo,Peru

In this pilot study, conducted in summer 2002, the authors measured blood lead levels (BLLs) for 118 subjects in the city of Trujillo, Peru, where leaded gasoline is in the process of being phased out. Subjects included bus drivers, combi (minivan) drivers, street vendors, newspaper vendors, traffic police, taxi drivers, gas station attendants, children living both near and distant from gas stations, pregnant women, and office workers (controls). The highest BLLs were 9.2 μg/dl and 9.3 μg/dl from a child who lived near a gas station and from a traffic policeman, respectively; however, all BLLs were below the U.S. Centers for Disease Control and Prevention's advisory level of concern (10 μg/dl). Office workers (n = 8) and pregnant women (n = 36) had significantly lower BLLs (geometric mean ± standard deviation = 2.1 ± 0.7 μg/dl, p < 0.022; and 2.5 ± 1.1 μg/dl, p < 0.008, respectively) than total traffic-exposed workers (n = 48; 3.2 ± 1.8 μg/dl). BLLs of children living near gas stations (n = 17; 3.7 ± 2.2 μg/dl) were marginally higher (p = 0.07) than for children not living near gas stations (n = 9; 2.9 ± 1.1 μg/dl). The study was limited by small sample size and the fact that the data were based on a convenience sample not fully representative of the cohorts studied. Nevertheless, the authors' findings suggest that leaded gasoline use in Trujillo continues to affect BLLs in traffic-exposed populations.     

Determinants of Blood Lead Levels across the Menopausal Transition

In this study, the authors sought to evaluate the impact of menopause on lead remobilization from bone-lead stores. The study was conducted between 1993 and 1995 in Mexico City and included 903 women (mean age = 46.8 y [standard deviation = 8.2 y]). Participants provided information about reproductive variables and known risk factors for high PbB levels. PbB levels were determined with graphite furnace atomic absorption spectrophotometry. The authors used linear-regression models to describe the relationship between PbB levels and variables of interest. PbB levels ranged from 1.0 μg/dl to 43.8 μg/dl (mean = 11.0 μg/dl). Menopausal women at baseline had the highest PbB levels; the mean difference between pre- and postmenopausal women was 0.76 μg/dl (95% confidence interval = 0.024, 1.48). We observed an inverted U-shaped relationship between PbB level and age. The highest PbB levels were observed in women aged 47-50 y. Other important predictors of PbB levels were use of lead-glazed ceramics, number of pregnancies, history of cigarette smoking, and height. Our results support the hypothesis that bone lead may be mobilized during menopause and may constitute an important source of exposure.     

The evidence that lead increases the risk for spontaneous abortion

BACKGROUND: Reports from a period spanning more than a century, and covering occupationally exposed women in several countries, support an increase in pregnancy loss from high maternal lead exposures. Nevertheless, most studies conducted among populations with low/moderate exposures have provided little evidence of an association with pregnancy loss, or in particular, spontaneous abortions. METHODS: A critique of these low/moderate level studies reveals small sample sizes, problems in definition or ascertainment of outcome, lack of control for confounding, and/or deficiencies in the exposure assessment. For estimating exposure, either an ecologic measure was used, or individual biologic specimens were taken but attention was not paid to the timing of measurement of lead levels in these samples. A prospective study that overcame most of the deficiencies of previous studies enrolled pregnant women in Mexico City with low-to-moderate-level lead exposures, collected blood specimens during their first trimester, and ascertained spontaneous abortions by week 20. A key design element of this study was the use of incidence-density-matched controls in order to achieve comparable opportunity for the outcome and comparable timing of exposure measurements. The latter is especially important because blood lead levels are altered by pregnancy. RESULTS: In the prospective Mexico City Study, a striking dose-response relation between blood lead and risk of spontaneous abortion was found: the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1-3.1) for every 5 microg/dL increase in blood lead. CONCLUSIONS: Low-to-moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to U.S. general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations. Further research is needed to confirm the association, to delineate the role of maternal vs. paternal exposures, and to assess increases in menstrual variability as an explanation for this finding.     

Occupational exposure to antineoplastic agents: self-reported miscarriages and stillbirths among nurses and pharmacists.

Insult to the germ cells of an ovum or sperm prior to pregnancy as well as exposures to a fetus during pregnancy can affect the outcome of a pregnancy. Antineoplastic agents are mutagenic and teratogenic, so the potential effects of exposure on reproduction are of concern to the workers who handle them. This study investigates pregnancy loss associated with occupational exposures to antineoplastic drugs by comparing rates of spontaneous abortion and stillbirths for pregnancies without antineoplastic exposure and exposed pregnancies in which the pregnant woman or the father handled antineoplastic agents either before or during the pregnancy. A total of 7094 pregnancies of 2976 pharmacy and nursing staff were examined. After age during pregnancy, prior gravidity, maternal smoking during the pregnancy, and occurrence of a spontaneous abortion or stillbirth in a prior pregnancy were controlled for, exposure of the mother to or the handling of antineoplastic agents during the pregnancy was associated with a significantly increased risk of spontaneous abortion (odds ratio = 1.5; 95% confidence interval, 1.2 to 1.8) and combined risk of spontaneous abortion and stillbirth (odds ratio = 1.4; 95% confidence interval, 1.2 to 1.7) but not stillbirth alone. Among the wives of exposed men, too few stillbirths occurred to allow analysis. However, for spontaneous abortion and any loss, the patterns of increased risk were similar to those seen for women, although the odds ratios were not statistically significant.