Deciphering molecular basis of pesticide-induced recurrent pregnancy loss: insights from transcriptomics analysis.

Recent studies have revealed a notable connection between pesticide exposure and Recurrent Pregnancy Loss (RPL), yet the precise molecular underpinning of this toxicity remains elusive. Through the alignment of Differentially Expressed Genes (DEGs) of healthy and RPL patients with the target genes of 9 pesticide components, we identified a set of 12 genes responsible for RPL etiology. Interestingly, biological process showed that besides RPL, those 12 genes also associated with preeclampsia and cardiovascular disease. Enrichment analysis showed the engagement of these genes associated with essential roles in the molecular transport of small molecules, as well as the aldosterone-regulated sodium reabsorption, endocrine and other factor-regulated calcium reabsorption, mineral absorption, ion homeostasis, and ion transport by P-type ATPases. Notably, the crosstalk targets between pesticide components played crucial roles in influencing RPL results, suggesting a role in attenuating pesticide agents that contribute to RPL. It is important to note that non-significant concentration of the pesticide components observed in both control and RPL samples should not prematurely undermine the potential for pesticides to induce RPL in humans. This study emphasizes the complexity of pesticide induced RPL and highlights avenues for further research and precautionary measures.

Fondaparinux Results in Similar Pregnancy Outcomes with Lower Adverse Reaction Rates Compared to Low Molecular Weight Heparin in Chinese Recurrent Miscarriage Women.

Fondaparinux inhibits thrombin generation by inactivating factor Xa, which has the potential to treat recurrent miscarriage (RM). However, more clinical evidence is required to support its application in Chinese women with RM. This research aimed to compare the live birth rate, gestational weeks at delivery, birth weight, Apgar score of newborns, and adverse reaction rates between fondaparinux and low molecular weight heparin (LMWH) in Chinese women with RM. Totally, 132 women with RM treated with fondaparinux or LMWH were included in this retrospective study. According to the corresponding treatment, women with RM were divided into the fondaparinux cohort (N = 45) and LMWH cohort (N = 87). The live birth rate was 68.9% in the fondaparinux cohort and 56.3% in the LMWH cohort, which was not different between the two cohorts (P = 0.161). Multivariable logistics regression analysis suggested that only previous miscarriage times (≥ 4 times vs. < 4 times) were independently related to a lower possibility of live birth in women with RM (odds ratio = 0.431, P = 0.036). It was also observed that gestational weeks at delivery (38.1 ± 1.4 vs. 37.7 ± 1.7 weeks) (P = 0.258), birth weight (2,923.7 ± 355.0 vs. 2,807.8 ± 334.0 g) (P = 0.144), and Apgar score of newborns (9.8 ± 0.5 vs. 9.6 ± 0.8) (P = 0.175) were not different between the fondaparinux cohort and LMWH cohort. Inspiringly, the total adverse reaction rate was reduced in the fondaparinux cohort vs. the LMWH cohort (20.0% vs. 37.9%) (P = 0.036). Fondaparinux results in similar pregnancy outcomes with lower adverse reaction rates compared to LMWH in Chinese women with RM.

Environmental BPDE induced human trophoblast cell apoptosis by up-regulating lnc-HZ01/p53 positive feedback loop.

Human trophoblast cell apoptosis may induce miscarriage. Trophoblast cells are sensitive to environmental BaP-7,8-dihydrodiol-9,10-epoxide (BPDE). However, how BPDE induces human trophoblast cell apoptosis is still largely elusive. In this work, we used BPDE-treated human trophoblast cells and villous tissues collected from recurrent miscarriage and health control groups to explore the underlying mechanism of BPDE-induced human trophoblast cell apoptosis. Continued with our recent work, we found that lncRNA HZ01 (lnc-HZ01) could induce human trophoblast cell apoptosis. In mechanism, lnc-HZ01 up-regulated p53 expression level by suppressing its MDM2-mediated proteasomal degradation. Meanwhile, we found that p53 acted as lnc-HZ01 transcription factor and promoted lnc-HZ01 transcription. Thus, lnc-HZ01 and p53 composed a positive feedback loop in human trophoblast cells. In normal trophoblast cells, relatively low levels of lnc-HZ01 and p53 suppressed p53/caspase-3 apoptosis pathway, giving normal pregnancy. Upon BPDE exposure, BPDE up-regulated the expression levels of lnc-HZ01 and p53, triggered this positive feedback loop, activated the p53/caspase-3 apoptosis pathway, and then induced miscarriage. Collectively, we discovered new mechanism by which lnc-HZ01 regulated BPDE-induced human trophoblast cell apoptosis, providing scientific basis for the diagnosis and treatment of unexplained recurrent miscarriage.

Levothyroxine in euthyroid thyroid peroxidase antibody positive women with recurrent pregnancy loss (T4LIFE trial): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Women positive for thyroid peroxidase antibodies (TPO-Ab) have a higher risk of recurrent pregnancy loss. Evidence on whether levothyroxine treatment improves pregnancy outcomes in women who are TPO-Ab positive women with recurrent pregnancy loss is scarce. The aim of this study was to determine if levothyroxine increases live birth rates in women who were TPO-Ab positive with recurrent pregnancy loss and normal thyroid function. METHODS: The T4LIFE trial was an international, double-blind, placebo-controlled, phase 3 study done in 13 secondary and tertiary hospitals in the Netherlands, one tertiary hospital in Belgium, and one tertiary hospital in Denmark. Women (18-42 years) who were TPO-Ab positive, had two or more pregnancy losses, and had a thyroid stimulating hormone (TSH) concentration within the institutional reference range were eligible for inclusion. Women were excluded if they had antiphospholipid syndrome (lupus anticoagulant, anticardiolipin IgG or IgM antibodies, or ß2-glycoprotein-I IgG or IgM antibodies), other autoimmune diseases, thyroid disease, previous enrolment in this trial, or contraindications for levothyroxine use. Before conception, women were randomly assigned (1:1) to receive either levothyroxine or placebo orally once daily. The daily dose of levothyroxine was based on preconception TSH concentration and ranged from 0·5-1·0 µg/kg bodyweight. Levothyroxine or placebo was continued until the end of pregnancy. The primary outcome was live birth, defined as the birth of a living child beyond 24 weeks of gestation measured in the intention-to-treat population. The trial was registered within the Netherlands Trial Register, NTR3364 and with EudraCT, 2011-001820-39. RESULTS: Between Jan 1, 2013, and Sept 19, 2019, 187 women were included in the study: 94 (50%) were assigned to the levothyroxine group and 93 (50%) were assigned to the placebo group. The trial was prematurely stopped when 187 (78%) of the 240 predefined patients had been included because of slow recruitment. 47 (50%) women in the levothyroxine group and 45 (48%) women in the placebo group had live births (risk ratio 1·03 [95% CI 0·77 to 1·38]; absolute risk difference 1·6% [95% CI -12·7 to 15·9]). Seven (7%) women in the levothyroxine group and seven (8%) in the placebo group reported adverse events, none of them were directly related to the study procedure. INTERPRETATION: Compared with placebo, levothyroxine treatment did not result in higher live birth rates in euthyroid women with recurrent pregnancy loss who were positive for TPO-Ab. On the basis of our findings, we do not advise routine use of levothyroxine in women who are TPO-Ab positive with recurrent pregnancy loss and normal thyroid function. FUNDING: Dutch Organization for Health Research and Development, Fonds NutsOhra, Dutch Patient Organization of Thyroid Disorders, the Jan Dekkerstichting and Dr Ludgardine Bouwmanstichting, and a personal donation through the Dutch Patient Organization of Thyroid Disorders.

Environmental exposure to bisphenol analogues and unexplained recurrent miscarriage: A case-control study.

The use of bisphenol A (BPA) has been substantially limited since 2010 due to its toxicity to human health. A group of bisphenol analogues that are structurally similar to BPA have been developed as the alternatives and used widely. The reproductive toxicity of these emerging chemicals has caused substantial concerns in recent years. Whether bisphenol analogues affect miscarriage, especially unexplained recurrent miscarriage (URM), remains to be explored. We conducted a hospital-based, case-control study with 1180 URM cases and 571 controls in China from 2014 to 2016. Concentrations of six bisphenol analogues (BPA, BPAF, BPAP, BPB, BPP and BPS) were measured in the urine samples collected at median intervals of 7.6 months after last miscarriage (interquartile ranges: 4.8, 14.7 months). Multiple logistic regression, Bayesian kernel machine regression (BKMR) and quantile g-computation (q-gcomp) were used to assess the relationship of bisphenol analogues with URM risk. We observed significantly higher levels of all urinary bisphenols in the cases than the controls. After controlling for potential confounders, bisphenol analogues were significantly associated with increased odds of URM in varying degrees. A dose-response pattern was observed for the associations of BPAF, BPAP and BPB quartiles with URM. The mixed exposure of six bisphenol analogues was positively associated with the risk of URM (adjusted odds ratio (aOR) = 1.25; 1.11-1.42), which was mainly driven by BPAP (60.1%), BPAF (25.1%) and BPA (14.8%). After age stratification, the risks tended to be higher in women aged 30 years or older, compared to women <30 years. Our large case-control study indicates that environmental exposure to bisphenol analogues is associated with an increased risk of URM. Older women may be more vulnerable to the insult.

Environmental Pollutant Benzo[a]pyrene Upregulated Long Non-coding RNA HZ07 Inhibits Trophoblast Cell Migration by Inactivating PI3K/AKT/MMP2 Signaling Pathway in Recurrent Pregnancy Loss.

Benzo(a)pyrene (BaP) is a ubiquitous environmental endocrine-disrupting chemical that is known to have toxic effects on reproduction. However, the underlying mechanisms describing how BaP and its metabolite benzo[a]pyrene-7, 8-diol-9, 10-epoxide (BPDE) induce recurrent pregnancy loss (RPL) are still largely unclear. In this study, we identified a novel long non-coding RNA (lnc-HZ07, NCBI MT936329) that was upregulated in trophoblast cells after exposure to BPDE, and lnc-HZ07 expression was significantly higher in RPL villous tissues than that in control villous tissues. Knockdown of lnc-HZ07 promoted trophoblast cell migration, whereas overexpression of lnc-HZ07 inhibited trophoblast cell migration. Further study showed that lnc-HZ07 inhibited trophoblast migration by downregulating matrix metalloproteinase 2 (MMP2) expression via dephosphorylation of AKT. These results demonstrated a novel regulatory pathway in which BaP downregulated AKT phosphorylation and inhibited MMP2 expression by upregulating lnc-HZ07, suggesting that lnc-HZ07 could be considered as a potential pathological marker of BaP-induced RPL and therapeutic target for this disease.

Environmental Pollutant Benzo[a]pyrene Induces Recurrent Pregnancy Loss through Promoting Apoptosis and Suppressing Migration of Extravillous Trophoblast.

METHODS: The implantation sites, fetus resorption, and abnormal fetuses were studied in pregnant mice treated with different doses of BaP by oral gavage from day 1 to day 10 of gestation. Additionally, apoptosis and related signaling pathway, and the migration and invasion of trophoblasts, were assessed before and after exposure of BPDE in Swan 71 trophoblast cell. Besides, the migration and invasion, and its related signaling pathway, were assessed in villi obtained from women. RESULTS: We observed a concentration-dependent incidence of abnormal murine fetuses, beginning with 0.1 mg/kg BaP; with a BaP concentration of 2 mg/kg, no fetuses developed. Correspondingly, a BPDE concentration-dependent apoptosis of human trophoblasts. Beginning with 0.5 µM BPDE exposure, Bax/Caspase-3 were increased and Bcl-2 decreased. Furthermore, BPDE also inhibited, in a dose-dependent manner, the migration of villous explants from elective abortion women, consistent with the reduced migration of villous explants from women with recurrent pregnancy loss (RPL), and reduced the cell immigration in Swan 71 trophoblasts, in a dose-dependent manner measured by transwell assays. CONCLUSIONS: Our study results provide mechanistic insight to the effect of BPDE on trophoblast dysfunction through enhanced cell apoptosis and inhibited migration, providing further experimental evidence to the causative links between BaP exposure and PRL.

[Association of arsenic with unexplained recurrent spontaneous abortion: a case-control study].

Objective: To explore the association of arsenic with unexplained recurrent spontaneous abortion (URSA). Methods: A case-control study was conducted to select URSA patients who were admitted to the Beijing Maternal and Child Health Care Hospital affiliated to Capital Medical University from April to October 2018 as a case group. Women who had a normal pregnancy in the Family Planning Department of the hospital but volunteered to have an abortion were selected as a control group. The case and control group were paired in a 1: 1 ratio. The inclusion criteria of the case group were patients with newly diagnosed recurrent spontaneous abortion who had clinically confirmed more than 2 spontaneous abortions and had 20 weeks prior to pregnancy, excluding patients with recurrent spontaneous abortion caused by abnormal blood coagulation (anti-phospholipid antibody positive), abnormal physiological anatomy (B-ultrasound), abnormal immune factors (anti-nuclear antibody positive, anti-cardiolipin antibody, etc.), genetic chromosomal abnormalities (karyotype analysis) and pathogenic microbial infection. The control group was matched according to the age of the case group (±3 years old) and the gestational age (±2 weeks) to exclude adverse pregnancy outcomes such as stillbirth, congenital malformation, premature delivery and low birth weight infants. A total of 192 subjects were included. Questionnaires were used to collect information of all subjects, and 12 ml of peripheral venous blood was collected to detect blood arsenic levels. Blood arsenic levels were divided into low concentration group (<1.00 µg/L), medium concentration group (1.00-1.50 µg/L) and high concentration group (>1.50 µg/L). The multivariate conditional logistic regression was performed to analyze the relationship between blood arsenic exposure and URSA and explore the influencing factors of blood Arsenic. Results: The geometric mean values of blood arsenic level in the cases group and control group were 1.68 (1.50-1.86) µg/L and 1.26 (1.17-1.37) µg/L, respectively. The blood arsenic level in the case group was significantly higher than that in the control group (P<0.05). The results of multivariate conditional logistic regression analysis showed that after adjusting for tobacco exposure during pregnancy, pre-pregnancy body mass index and the effects of residential decoration in past five years, the risk of URSA was higher in the high-concentration group compared with the low-concentration group (OR=2.56, 95%CI:1.06-6.24). Conclusion: Blood arsenic may increase the risk of URSA in women of childbearing age.

New studies of low-molecular-weight heparin in pregnancy.

Several aspects of the diagnostic and therapeutic management of women with venous thrombosis are uncertain, because of the absence of adequately sized observational or intervention studies. Here, I will discuss the rationale and design of two currently ongoing investigator-initiated, international, randomized controlled trials of LMWHin pregnancy. The Highlow study (www.highlowstudy.org; NCT Clinicaltrials.gov) 01828697) investigates two doses of low-molecular-weight heparin to prevent recurrent venous thromboembolism (VTE) in pregnant women with a history of VTE. The ALIFE2 study (www.alife2study.org; www.trialregister.nl, NTR 3361) investigates the effect of LMWH on live birth in women with inherited thrombophilia and two or more miscarriages.

Women's risk of repeat abortions is strongly associated with alcohol consumption: a longitudinal analysis of a Russian national panel study, 1994-2009.

Abortion rates in Russia, particularly repeat abortions, are among the highest in the world, and abortion complications make a substantial contribution to the country's high maternal mortality rate. Russia also has a very high rate of hazardous alcohol use. However, the association between alcohol use and abortion in Russia remains unexplored. We investigated the longitudinal predictors of first and repeat abortion, focussing on women's alcohol use as a risk factor. Follow-up data from 2,623 women of reproductive age (16-44 years) was extracted from 14 waves of the Russian Longitudinal Monitoring Survey (RLMS), a nationally representative panel study covering the period 1994-2009. We used discrete time hazard models to estimate the probability of having a first and repeat abortion by social, demographic and health characteristics at the preceding study wave. Having a first abortion was associated with demographic factors such as age and parity, whereas repeat abortions were associated with low education and alcohol use. After adjustment for demographic and socioeconomic factors, the risk of having a repeat abortion increased significantly as women's drinking frequency increased (P<0.001), and binge drinking women were significantly more likely to have a repeat abortion than non-drinkers (OR 2.28, 95% CI 1.62-3.20). This association was not accounted for by contraceptive use or a higher risk of pregnancy. Therefore the determinants of first and repeat abortion in Russia between 1994-2009 were different. Women who had repeat abortions were distinguished by their heavier and more frequent alcohol use. The mechanism for the association is not well understood but could be explained by unmeasured personality factors, such as risk taking, or social non-conformity increasing the risk of unplanned pregnancy. Heavy or frequent drinkers constitute a particularly high risk group for repeat abortion, who could be targeted in prevention efforts.

Maternal caffeine consumption and sine causa recurrent miscarriage.

OBJECTIVE: The objective of this study was to examine whether the risk of sine causa recurrent miscarriage is associated with caffeine consumption during the periconceptional period and early gestation after controlling for pregnancy-related symptoms. STUDY DESIGN: A retrospective case-control study was conducted in the Department of Obstetrics and Gynecology, University of Turin between 2008 and 2009. Fifty-two sine causa recurrent miscarriers and 260 healthy pregnant women were assessed. Data were analyzed using SPSS 17 for Windows. RESULTS: Caffeine consumption during the periconceptional period and early gestation was higher in sine causa recurrent miscarriers compared to healthy pregnant women. Moreover, each caffeine intake of 100mg/day was associated with an increased odds ratio for sine causa recurrent miscarriage of 2724 (p for trend 0.001; 95% confidence interval [CI], 2.715-2.733), after adjusting for relevant confounding covariates. CONCLUSION: Caffeine intake may increase the risk of sine causa recurrent miscarriage regardless of pregnancy-related symptoms and relevant covariates (such as age and tobacco use).

LMWH have no place in recurrent pregnancy loss: debate-against the motion.

The SPIN and ALIFE intervention trials apparently support that LMWHs should not be advocated in patients with idiopathic RPL. There are however some concerns. Epidemiology implies that most of the included patients shared recurrent regulatory embryonic losses associated with isolated cytogenetics defects, a dominant good prognosis entity which doesn't have to be treated. The real PL illness, idiopathic foetal loss with normal karyotypes, was a minority. Primary and secondary RPL cases were included, whose prognostic, applied to non-sporadic PLs, cannot be similar. Thrombophilic patients were a minority, despite existing data suggesting a LMWH beneficial effect. LMWHs were associated with LDA, previously suspected to be deleterious in PL patients with thrombophilia. The two indubitably planned-to-be negative trials will positively contribute to limit aberrant LMWH treatments in non-selected RPL women cared without comprehensive clinical categorisation. This is not the real clinical target for LMWHs, which still has to be fully investigated.

Habitual caffeine intake in women of childbearing age.

BACKGROUND: For women, delayed conception and recurrent pregnant loss are just a few of the health implications associated with a caffeine-rich diet (Mol. Hum. Reprod., 11, 357). At present there is a deficit of prospective research measuring current habitual intakes of caffeine in UK women. The purpose of the current study was to collect up-to-date baseline data to assess caffeine intake and knowledge in a group of women (aged 16-45 years). METHODS: Seventy Caucasian subjects (mean age 30.4 +/- 8.7 years) were recruited from business offices within the Manchester area. Each participant completed a 3-day food diary and lifestyle questionnaire. RESULTS: The mean intake of caffeine was 173.95 mg day(-1) (+/-128.39 mg day(-1)). Eighteen per cent of subjects exceeded caffeine guidelines and consumed 300 mg caffeine or more each day. Subjects consuming over 300 mg day(-1) were more likely to be older (P = 0.016) and smokers (P = 0.000). Individuals given previous advice about caffeine and health, had lower intakes (P = 0.002). CONCLUSIONS: Many women are unaware of health perturbations associated with caffeine consumption. A diet abundant in caffeine may result in delayed conception, infertility and increased risk of osteoporosis, cardiovascular disease and cancer later in life. Such information needs to be conveyed to the public sector. Future research is also required to devise specific caffeine guidelines, particularly safe upper limits.

Analysis of sperm karyotypes in a patient treated with griseofulvin.

Griseofulvin is known to interfere with chromosome segregation by binding to microtubule-associated proteins. Studies in mouse germ cells have demonstrated that griseofulvin can induce aneuploidy (numerical chromosome abnormalities) at therapeutic concentrations. The aim of this study was to determine if chronic griseofulvin treatment led to an increased frequency of sperm chromosome abnormalities in one male subject. We analyzed 290 full sperm karyotypes using the human sperm-hamster oocyte fusion system. The frequency of X- and Y-bearing sperm was equal. There was no increase in the frequency of numerical (1.7%) or structural (9.3%) abnormalities in the subject compared to unexposed controls. Although reassuring, this is the first report on this subject and future studies are needed to assess the risk of griseofulvin.

Exposure to bisphenol A is associated with recurrent miscarriage.

BACKGROUND: Little is known about the influence of high exposure to bisphenol A on recurrent miscarriage and immunoendocrine abnormalities. METHODS: Serum bisphenol A, antiphospholipid antibodies (aPLs), antinuclear antibodies (ANAs), natural killer cell (NK) activity, prolactin, progesterone, thyroid-stimulating hormone (TSH) and free T4 were examined in 45 patients with a history of three or more (3-11) consecutive first-trimester miscarriages and 32 healthy women with no history of live birth and infertility. Subsequent pregnancy outcome and embryonic karyotype of abortuses were examined prospectively. RESULTS: The mean+/-SD values for bisphenol A in patients were 2.59+/-5.23 ng/ml, significantly higher than the 0.77+/-0.38 ng/ml found for control women (P=0.024). High exposure to bisphenol A was associated with the presence of ANAs but not hypothyroidism, hyperprolactinaemia, luteal phase defects, NK cell activity or aPLs. A high level of bisphenol A in itself did not predict subsequent miscarriage. CONCLUSION: Exposure to bisphenol A is associated with recurrent miscarriage.

Caffeine intake, CYP1A2 polymorphism and the risk of recurrent pregnancy loss.

Some case-control studies have demonstrated that caffeine intake and high CYP1A2 activity increase risks of recurrent pregnancy loss (RPL) but the multifactorial effect is obscure. To investigate whether susceptible women who have more caffeine intake are at high risk of RPL, a case-control study of 58 cases with two or more RPL and fertile 147 controls was performed. The association between daily caffeine intake together with CYP1A21F (AA versus CA and CC) genotype and RPL was assessed. Without consideration of the genotype, there were no significant differences of the RPL risk in proportion to daily caffeine intake [less than 100 mg (reference); 100-299 mg: odds ratio (OR), 1.29; 95% confidence interval (CI), 0.66-2.50; 300 mg or more: OR, 1.82; 95% CI, 0.72-4.58; P for trend, 0.20]. However, the RPL risk significantly increased only among women who had homozygous CYP1A21F alleles with a dosage effect of daily caffeine intake [less than 100 mg (reference); 100-299 mg: OR, 1.94; 95% CI, 0.57-6.66; 300 mg or more: OR, 5.23; 95% CI, 1.05-25.9; P for trend, 0.03]. It was demonstrated for the first time that an increase in caffeine intake deteriorates the fecundity among susceptible women.

PCBs, hexachlorobenzene and DDE are not associated with recurrent miscarriage.

PROBLEM: A case-control study was designed to evaluate any associations between high exposure to polychlorinated biphenyls (PCB), hexachlorobenzene (HCB) and the 1,1,1,-trichloro-2,2-bis (p-chlorophenyl) ethane (DDT) metabolite 1,1-dichloro-2,2-bis (p-chlorophenyl) ethylene (DDE) and recurrent miscarriage and immunoendocrine abnormalities. METHODS OF STUDY: A total of 18 kinds of co-planer PCBs, HCB, DDE, natural killer cell (NK) activity, antiphospholipid antibodies, antinuclear antibody, prolactin, progesterone, thyroid-stimulating hormone (TSH) and free T4 were examined in 45 patients with a history of three or more (3-11) consecutive first-trimester miscarriages and 30 healthy women with no history of live birth and infertility. RESULTS: There were no differences in mean +/- S.D. values in serum samples for PCBs, HCB and DDE between patients and controls. Hypothyroidism, hyperprolactinemia, luteal phase defects, NK cell activity and the presence of autoantibodies were also not associated with levels of any of the compounds in the patients. CONCLUSION: PCBs, HCB and DDE are not associated with miscarriage and immunoendocrine abnormalities in patients with a history of recurrent miscarriage.

Environmental toxins associated with recurrent pregnancy loss.

Couples experiencing recurrent pregnancy loss are often concerned that toxins within the environment have contributed to their reproductive difficulty. Questions posed by these couples to their health care providers are difficult to answer because scientifically accurate information regarding the reproductive impact of potential environmental toxins and other teratogens is not readily available. Heavy metals such as lead and mercury, organic solvents, alcohol, and ionizing radiation are confirmed environmental teratogens, and exposure could contribute to pregnancy loss. Caffeine, cigarette smoking, and hyperthermia are suspected teratogens, and the teratogenic impact of pesticides remains unknown. The teratogenic potential of multiple other environmental factors has been studied and is reviewed. Before definitive conclusions can be drawn regarding the teratogenicity of environmental exposures, several clinical factors need to be addressed, including gestational age at the time of exposure, the amount of toxin reaching the conceptus, the duration of exposure, the impact of other factors or agents to which the mother or her conceptus is simultaneously exposed, and the physiological status of the mother and conceptus. In addition, in a given population, the interrelationship between frequency of exposures,frequency of effects, and recognizability of adverse outcomes, such as spontaneous abortion, should be considered.