Epidemiology of Covid-19 in a Long-Term Care Facility in King County, Washington.

BACKGROUND: Long-term care facilities are high-risk settings for severe outcomes from outbreaks of Covid-19, owing to both the advanced age and frequent chronic underlying health conditions of the residents and the movement of health care personnel among facilities in a region. METHODS: After identification on February 28, 2020, of a confirmed case of Covid-19 in a skilled nursing facility in King County, Washington, Public Health-Seattle and King County, aided by the Centers for Disease Control and Prevention, launched a case investigation, contact tracing, quarantine of exposed persons, isolation of confirmed and suspected cases, and on-site enhancement of infection prevention and control. RESULTS: As of March 18, a total of 167 confirmed cases of Covid-19 affecting 101 residents, 50 health care personnel, and 16 visitors were found to be epidemiologically linked to the facility. Most cases among residents included respiratory illness consistent with Covid-19; however, in 7 residents no symptoms were documented. Hospitalization rates for facility residents, visitors, and staff were 54.5%, 50.0%, and 6.0%, respectively. The case fatality rate for residents was 33.7% (34 of 101). As of March 18, a total of 30 long-term care facilities with at least one confirmed case of Covid-19 had been identified in King County. CONCLUSIONS: In the context of rapidly escalating Covid-19 outbreaks, proactive steps by long-term care facilities to identify and exclude potentially infected staff and visitors, actively monitor for potentially infected patients, and implement appropriate infection prevention and control measures are needed to prevent the introduction of Covid-19.

COVID-19 in a Long-Term Care Facility - King County, Washington, February 27-March 9, 2020.

On February 28, 2020, a case of coronavirus disease (COVID-19) was identified in a woman resident of a long-term care skilled nursing facility (facility A) in King County, Washington.* Epidemiologic investigation of facility A identified 129 cases of COVID-19 associated with facility A, including 81 of the residents, 34 staff members, and 14 visitors; 23 persons died. Limitations in effective infection control and prevention and staff members working in multiple facilities contributed to intra- and interfacility spread. COVID-19 can spread rapidly in long-term residential care facilities, and persons with chronic underlying medical conditions are at greater risk for COVID-19-associated severe disease and death. Long-term care facilities should take proactive steps to protect the health of residents and preserve the health care workforce by identifying and excluding potentially infected staff members and visitors, ensuring early recognition of potentially infected patients, and implementing appropriate infection control measures.

Evaluation of electronic ambulatory care data for influenza-like illness surveillance, Washington State.

A growing number of outpatient providers utilize electronic health records (EHR) to identify patient visits for influenza-like illness (ILI) but no standard query guidance exists. We applied an ILI definition validated for emergency department data to EHR from outpatient networks and found ILI visits highly correlated with influenza laboratory detections. Incorporating ambulatory EHR into our ILI surveillance system increased the capacity by more than 300%. Electronic ambulatory care data could be used to augment or replace public health surveillance systems traditionally reliant on manual reporting.

An automated system for public health surveillance of school absenteeism.

Public Health-Seattle & King County established an automated system for monitoring school absenteeism data from 18 of 19 public school districts in King County, Washington. The system receives a daily aggregate count of the number of students enrolled and absent, stratified by school district, school name, and grade. A name and unique identifier are provided for each school and district, as well as the level (eg, elementary, middle, high, alternative, other) and zip code of each school. Files are transmitted to the health department daily and include data from the previous school day. Public Health-Seattle & King County developed a series of visualizations that summarize the data by day, week, and month for each level of stratification. The automated system for collecting and monitoring school absenteeism data was more acceptable, simple, timely, complete, and useful relative to traditional manual data collection methods.

A Population-Based Intervention to Improve Care Cascades of Patients With Hepatitis C Virus Infection.

Hepatitis C virus (HCV) infection is common in the United States and leads to significant morbidity, mortality, and economic costs. Simplified screening recommendations and highly effective direct-acting antivirals for HCV present an opportunity to eliminate HCV. The objective of this study was to increase testing, linkage to care, treatment, and cure of HCV. This was an observational, prospective, population-based intervention program carried out between September 2014 and September 2018 and performed in three community health centers, three large multiclinic health care systems, and an HCV patient education and advocacy group in King County, WA. There were 232,214 patients included based on criteria of documented HCV-related diagnosis code, positive HCV laboratory test or prescription of HCV medication, and seen at least once at a participating clinical site in the prior year. Electronic health record (EHR) prompts and reports were created. Case management linked patients to care. Primary care providers received training through classroom didactics, an online curriculum, specialty clinic shadowing, and a telemedicine program. The proportion of baby boomer patients with documentation of HCV testing increased from 18% to 54% during the project period. Of 77,577 baby boomer patients screened at 87 partner clinics, 2,401 (3%) were newly identified HCV antibody positive. The number of patients staged for treatment increased by 391%, and those treated increased by 1,263%. Among the 79% of patients tested after treatment, 95% achieved sustained virologic response. Conclusion: A combination of EHR-based health care system interventions, active linkage to care, and clinician training contributed to a tripling in the number of patients screened and a more than 10-fold increase of those treated. The interventions are scalable and foundational to the goal of HCV elimination.

Accuracy and cost-effectiveness of cervical cancer screening by high-risk human papillomavirus DNA testing of self-collected vaginal samples.

OBJECTIVE: Estimate the accuracy and cost-effectiveness of cervical cancer screening strategies based on high-risk human papillomavirus (HPV) DNA testing of self-collected vaginal samples. MATERIALS AND METHODS: A subset of 1,665 women (age range, 18-50 y) participating in a cervical cancer screening study were screened by liquid-based cytology and by high-risk HPV DNA testing of both self-collected vaginal swab samples and clinician-collected cervical samples. Women with positive/abnormal screening test results and a subset of women with negative screening test results were triaged to colposcopy. On the basis of individual and combined test results, 5 screening strategies were defined. Estimates of sensitivity and specificity for cervical intraepithelial neoplasia grade 2 or worse were calculated, and a Markov model was used to estimate the incremental cost-effectiveness ratios for each strategy. RESULTS: Compared with cytology-based screening, high-risk HPV DNA testing of self-collected vaginal samples was more sensitive (68%, 95% CI = 58%-78% vs 85%, 95% CI = 76%-94%) but less specific (89%, 95% CI = 86%-91% vs 73%, 95% CI = 67%-79%). A strategy of high-risk HPV DNA testing of self-collected vaginal samples followed by cytology triage of HPV-positive women was comparably sensitive (75%, 95% CI = 64%-86%) and specific (88%, 95% CI = 85%-92%) to cytology-based screening. In-home self-collection for high-risk HPV DNA detection followed by in-clinic cytology triage had a slightly lower lifetime cost and a slightly higher quality-adjusted life year (QALY) expectancy than did cytology-based screening (incremental cost-effectiveness ratio of triennial screening compared with no screening was $9,871/QALY and $12,878/QALY, respectively). CONCLUSIONS: Triennial screening by high-risk HPV DNA testing of in-home, self-collected vaginal samples followed by in-clinic cytology triage was cost-effective.

Design of an Enhanced Public Health Surveillance System for Hepatitis C Virus Elimination in King County, Washington.

INTRODUCTION: With the goal of eliminating hepatitis C virus (HCV) as a public health problem in Washington State, Public Health-Seattle & King County (PHSKC) designed a Hepatitis C Virus Test and Cure (HCV-TAC) data system to integrate surveillance, clinical, and laboratory data into a comprehensive database. The intent of the system was to promote identification, treatment, and cure of HCV-infected persons (ie, HCV care cascade) using a population health approach. MATERIALS AND METHODS: The data system automatically integrated case reports received via telephone and fax from health care providers and laboratories, hepatitis test results reported via electronic laboratory reporting, and data on laboratory and clinic visits reported by 6 regional health care systems. PHSKC examined patient-level laboratory test results and established HCV case classification using Council of State and Territorial Epidemiologists criteria, classifying patients as confirmed if they had detectable HCV RNA. RESULTS: The data enabled PHSKC to report the number of patients at various stages along the HCV care cascade. Of 7747 HCV RNA-positive patients seen by a partner site, 5377 (69%) were assessed for severity of liver fibrosis, 3932 (51%) were treated, and 2592 (33%) were cured. PRACTICE IMPLICATIONS: Data supported local public heath surveillance and HCV program activities. The data system could serve as a foundation for monitoring future HCV prevention and control programs.

Association between school closure and subsequent absenteeism during a seasonal influenza epidemic.

BACKGROUND: Mathematical models suggest that social distancing measures, such as school closures, may mitigate community transmission during an influenza pandemic. Because closures are disruptive to schools and families, they are rarely employed during seasonal influenza outbreaks. A rare circumstance enabled us to examine the association between school closure and absenteeism during a seasonal influenza outbreak when half of King County, Washington public schools closed for a winter recess 19-23 February 2007, while half remained open for all or part of the week. METHODS: Using absenteeism as a proxy for influenza activity, we tested the hypothesis that schools on break would experience lower rates of post-break absenteeism than schools remaining open. We conducted daily retrospective and prospective surveillance from 5 February-9 March 2007 in schools on break (n = 256) and in session (n = 205). We use generalized estimating equations with Poisson distribution to evaluate whether mean absenteeism after the break differed between schools on break and those in session, adjusting for baseline absenteeism and repeated measurements by schools over time. RESULTS: Results indicate no difference in post-break absenteeism in schools on break compared with schools that remained in session (relative risk = 1.07 [95% confidence interval = 0.96-1.20]). This result held in elementary schools (1.00 [0.91-1.10]), where absenteeism patterns are thought to be most representative of community influenza activity. CONCLUSION: We did not find that school closure during a seasonal influenza outbreak reduced subsequent absenteeism. However, limitations in this "natural experiment" hampered our ability to detect a benefit if one truly was present.

Carbon monoxide epidemic among immigrant populations: King County, Washington, 2006.

OBJECTIVES: We investigated an outbreak of carbon monoxide (CO) poisoning after a power outage to determine its extent, identify risk factors, and develop prevention measures. METHODS: We reviewed medical records and medical examiner reports of patients with CO poisoning or related symptoms during December 15 to 24, 2006. We grouped patients into households exposed concurrently to a single source of CO. RESULTS: Among 259 patients with CO poisoning, 204 cases were laboratory confirmed, 37 were probable, 10 were suspected, and 8 were fatal. Of 86 households studied, 58% (n = 50) were immigrant households from Africa (n = 21), Asia (n = 15), Latin America (n = 10), and the Middle East (n = 4); 34% (n = 29) were US-born households. One percent of households was European (n = 1), and the origin for 7% (n = 6) was unknown. Charcoal was the most common fuel source used among immigrant households (82%), whereas liquid fuel was predominant among US-born households (34%). CONCLUSIONS: Educational campaigns to prevent CO poisoning should consider immigrants' cultural practices and languages and specifically warn against burning charcoal indoors and incorrect ventilation of gasoline- or propane-powered electric generators.

Completeness of reporting of rabies postexposure prophylaxis in King County, Washington.

The completeness of rabies postexposure prophylaxis (PEP) reporting was evaluated in King County, Washington State. Information on rabies immune globulin prescriptions was obtained from hospital pharmacies associated with emergency departments in King County from 2003 to June 2006. Rabies immune globulin is given at the initiation of rabies PEP which is usually started at emergency departments. Because pharmacies are not regular sources of rabies PEP reporting, we compared pharmacy cases with cases reported via routine passive surveillance methods. A capture-recapture method was used to calculate the estimated number of unreported cases from all sources. Reporting completeness was calculated by dividing the number of cases reported via routine surveillance with the sum of reported and estimated unreported cases. Seventy-one unreported rabies PEP cases were identified by comparing previously reported cases with pharmacy cases. A total of 128 cases were estimated to have been missed by the surveillance system. Overall reporting completeness was 62 percent increasing to almost 80 percent in 2005 and 2006. Our findings illustrate the importance of evaluating surveillance systems and suggest that it may be useful to institute active rabies PEP surveillance with emergency departments in addition to continuing educating healthcare providers and facilities about reporting.

A simulation study comparing aberration detection algorithms for syndromic surveillance.

BACKGROUND: The usefulness of syndromic surveillance for early outbreak detection depends in part on effective statistical aberration detection. However, few published studies have compared different detection algorithms on identical data. In the largest simulation study conducted to date, we compared the performance of six aberration detection algorithms on simulated outbreaks superimposed on authentic syndromic surveillance data. METHODS: We compared three control-chart-based statistics, two exponential weighted moving averages, and a generalized linear model. We simulated 310 unique outbreak signals, and added these to actual daily counts of four syndromes monitored by Public Health--Seattle and King County's syndromic surveillance system. We compared the sensitivity of the six algorithms at detecting these simulated outbreaks at a fixed alert rate of 0.01. RESULTS: Stratified by baseline or by outbreak distribution, duration, or size, the generalized linear model was more sensitive than the other algorithms and detected 54% (95% CI = 52%-56%) of the simulated epidemics when run at an alert rate of 0.01. However, all of the algorithms had poor sensitivity, particularly for outbreaks that did not begin with a surge of cases. CONCLUSION: When tested on county-level data aggregated across age groups, these algorithms often did not perform well in detecting signals other than large, rapid increases in case counts relative to baseline levels.

National and Regional Representativeness of Hospital Emergency Department Visit Data in the National Syndromic Surveillance Program, United States, 2014.

OBJECTIVE: We examined the representativeness of the nonfederal hospital emergency department (ED) visit data in the National Syndromic Surveillance Program (NSSP). METHODS: We used the 2012 American Hospital Association Annual Survey Database, other databases, and information from state and local health departments participating in the NSSP about which hospitals submitted data to the NSSP in October 2014. We compared ED visits for hospitals submitting data with all ED visits in all 50 states and Washington, DC. RESULTS: Approximately 60.4 million of 134.6 million ED visits nationwide (~45%) were reported to have been submitted to the NSSP. ED visits in 5 of 10 regions and the majority of the states were substantially underrepresented in the NSSP. The NSSP ED visits were similar to national ED visits in terms of many of the characteristics of hospitals and their service areas. However, visits in hospitals with the fewest annual ED visits, in rural trauma centers, and in hospitals serving populations with high percentages of Hispanics and Asians were underrepresented. CONCLUSIONS: NSSP nonfederal hospital ED visit data were representative for many hospital characteristics and in some geographic areas but were not very representative nationally and in many locations. Representativeness could be improved by increasing participation in more states and among specific types of hospitals. (Disaster Med Public Health Preparedness. 2016;10:562-569).

Liquid-based Papanicolaou smears without a transformation zone component: should clinicians worry?

OBJECTIVE: To evaluate whether ThinPrep smears without versus those with a transformation zone component were more likely to have falsely negative cytology findings. METHODS: Women aged 18-50 (N = 4389) attended one of three Planned Parenthood clinics between 1997 and 2001 for screening by ThinPrep Papanicolaou and polymerase chain reaction-based human papillomavirus (HPV) DNA testing. Women with 1) any cytologic abnormality, 2) high-risk HPV types, and 3) a random sample with normal Papanicolaou and negative HPV tests were offered repeat cytology, colposcopy, and biopsy. Cytology and biopsy diagnoses at the colposcopy visit were reviewed according to the presence (n = 3689) or absence (n = 700) of a transformation zone component at screening. RESULTS: Among women with normal cytology at screening, histologic detection of at least cervical intraepithelial neoplasia grade 2 (odds ratio 1.3, 95% confidence interval 0.5, 3.3) at colposcopy did not differ significantly between transformation zone-positive and zone-negative smears. Histologically confirmed cervical intraepithelial neoplasia grade 1 was detected more often among smears lacking a transformation zone component (odds ratio 2.0, confidence interval 1.0, 3.8). Transformation zone-negative smears were more common among older women, current oral contraceptive users, those past the 14th day of their last menstrual period, and those negative for high-risk HPV types. CONCLUSION: Absence of a transformation zone component in a screening ThinPrep Papanicolaou test was not associated with missed high-grade lesions. Based upon our data, we do not recommend repeat screening of reproductive-aged women with negative liquid-based tests and no cytologic evidence of a transformation zone component.

Collection and integration of clinical data for surveillance.

OBJECTIVE: The syndromic surveillance project at Public Health-Seattle & King County incorporates several data sources, including emergency department and primary care visit data collected and normalized through an automated mechanism. We describe significant changes made in this "second generation" of our system to improve data quality while complying with privacy and state public health reporting regulations. METHODS/RESULTS: The system uses de-identified visit and patient numbers to assure data accuracy, while shielding patient identity. Presently, we have 124,000 basic visit records (used to generate stratified denominators), and 29,000 surveillance records, from four emergency departments and a primary care clinic network. The system is capable of producing syndrome-clustered data sets for analysis. DISCUSSION: We have incorporated data collection techniques such as automated querying, report parsing, and HL7 electronic data interchange. We are expanding the system to include greater population coverage, and developing an understanding how to implement data collections more rapidly at individual hospital sites, as well as how best to prepare the data for analysis.

Risk factors for infections in international travelers: an analysis of travel-related notifiable communicable diseases.

BACKGROUND: We sought to describe travel-related illness among our residents and gain insight into targeting pre-travel health advice to prevent travel-related illness. METHODS: A supplemental travel questionnaire was developed and administered for cases with a legally notifiable communicable disease reported in 2011-2012, who spent at least part of their exposure period outside the United States. RESULTS: Among 451 cases meeting the eligibility criteria, 259 were interviewed. Forty four percent reported receiving pre-travel advice. Two-thirds adhered fully with risk behavior recommendations; 94% followed immunization recommendations partially or fully; and 84% adhered fully with malaria prophylaxis recommendations. The primary reasons for not obtaining pre-travel advice were being unaware of the need (47.5%), or believing they already knew what to do (34.5%). Adults (OR = 2.8, 95% CI = 1.4-5.5), males (OR = 1.8, 95% CI = 1.1-3.0), those born outside the United States (OR = 2.0, 95% CI = 1.1-3.7), and those with planning time under two weeks (OR = 4.8, 95% CI = 1.5-15.9) or travel duration less than 7 days (OR = 7.9, 95% CI = 3.0-20.9) were more likely to travel without seeking pre-travel advice. CONCLUSIONS: The majority of cases reported not receiving pre-travel advice. Understanding the predictors of failure to receive pre-travel advice may help target public health prevention efforts.

Usefulness of syndromic data sources for investigating morbidity resulting from a severe weather event.

OBJECTIVE: We evaluated emergency department (ED) data, emergency medical services (EMS) data, and public utilities data for describing an outbreak of carbon monoxide (CO) poisoning following a windstorm. METHODS: Syndromic ED data were matched against previously collected chart abstraction data. We ran detection algorithms on selected time series derived from all 3 data sources to identify health events associated with the CO poisoning outbreak. We used spatial and spatiotemporal scan statistics to identify geographic areas that were most heavily affected by the CO poisoning event. RESULTS: Of the 241 CO cases confirmed by chart review, 190 (78.8%) were identified in the syndromic surveillance data as exact matches. Records from the ED and EMS data detected an increase in CO-consistent syndromes after the storm. The ED data identified significant clusters of CO-consistent syndromes, including zip codes that had widespread power outages. Weak temporal gastrointestinal (GI) signals, possibly resulting from ingestion of food spoiled by lack of refrigeration, were detected in the ED data but not in the EMS data. Spatial clustering of GI-based groupings in the ED data was not detected. CONCLUSIONS: Data from this evaluation support the value of ED data for surveillance after natural disasters. Enhanced EMS data may be useful for monitoring a CO poisoning event, if these data are available to the health department promptly.

Infant pertussis epidemiology and implications for tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination: King County, Washington, 2002 through 2007.

OBJECTIVES: To describe the epidemiology of infant pertussis in King County, Washington, and to better understand the implications for tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccination among older children, adolescents, and adults. DESIGN: Retrospective analysis of reported pertussis cases among infants younger than 1 year, January 1, 2002, through December 31, 2007. SETTING: King County, Washington. PARTICIPANTS: Reported pertussis cases among infants younger than 1 year between 2002 and 2007. MAIN OUTCOME MEASURES: Bordetella pertussis from a household member or close contact was the primary exposure. The main outcome measures were age and vaccination status, incidence by race/ethnicity, suspected exposure, and Tdap eligibility of household members and close contacts. RESULTS: Among 176 confirmed cases of infants with pertussis, the median age was 3 months (age range, 0-11 months); 80.1% were younger than 6 months. Seventy-seven percent were age-appropriately vaccinated. Between 2002 and 2007, the overall mean annual incidence was 136 cases per 100,000 infant population. Compared with a mean annual incidence of 73 cases per 100,000 infant population among whites, the incidence was 246 cases per 100,000 infant population among blacks (rate ratio [RR], 3.37; 95% confidence interval [CI], 2.59-4.44) and 194 cases per 100,000 infant population among Hispanics (RR, 2.66; 95% CI, 2.02-3.53). Households were the suspected exposure location for 70.0% of cases. Case households had a median of 3 (range, 1-15) Tdap-eligible persons. CONCLUSIONS: The burden of infant pertussis in King County, Washington, was high between 2002 and 2007, especially among racial/ethnic minorities. Tdap vaccination of eligible household members and close contacts should be promoted as an additional means of protecting infants from pertussis.

Developing syndrome definitions based on consensus and current use.

OBJECTIVE: Standardized surveillance syndromes do not exist but would facilitate sharing data among surveillance systems and comparing the accuracy of existing systems. The objective of this study was to create reference syndrome definitions from a consensus of investigators who currently have or are building syndromic surveillance systems. DESIGN: Clinical condition-syndrome pairs were catalogued for 10 surveillance systems across the United States and the representatives of these systems were brought together for a workshop to discuss consensus syndrome definitions. RESULTS: Consensus syndrome definitions were generated for the four syndromes monitored by the majority of the 10 participating surveillance systems: Respiratory, gastrointestinal, constitutional, and influenza-like illness (ILI). An important element in coming to consensus quickly was the development of a sensitive and specific definition for respiratory and gastrointestinal syndromes. After the workshop, the definitions were refined and supplemented with keywords and regular expressions, the keywords were mapped to standard vocabularies, and a web ontology language (OWL) ontology was created. LIMITATIONS: The consensus definitions have not yet been validated through implementation. CONCLUSION: The consensus definitions provide an explicit description of the current state-of-the-art syndromes used in automated surveillance, which can subsequently be systematically evaluated against real data to improve the definitions. The method for creating consensus definitions could be applied to other domains that have diverse existing definitions.

Spring 2009 H1N1 influenza outbreak in King County, Washington.

BACKGROUND: In April 2009, King County, Washington, experienced a sustained outbreak of 2009 H1N1 influenza A. This report describes the epidemiology of that outbreak in King County, home to a diverse population of 1.9 million people. METHODS: The 2 primary sources of data are case investigations of reported laboratory-confirmed 2009 H1N1 influenza A and a population-based syndromic surveillance system that captures data from emergency departments (EDs). A syndromic category for influenza-like illness was defined based on chief complaint and diagnosis. RESULTS: ED visits for influenza-like illness peaked quickly in the first week of the outbreak and remained high for approximately 6 weeks, with school-age children accounting for the greater number of ED visits, followed by young adults. Children ages 0 to 4 years had the highest rate of hospitalization. Among reported cases, blacks, Asians, and Hispanics were more likely to be hospitalized. Predisposing factors associated with admission were immune compromise, chronic lung disease, chronic heart disease, pregnancy, diabetes, and asthma. Of people receiving antiviral treatment, 34% started their medication more than 2 calendar days after the onset of illness. Mean days between illness onset and antiviral treatment were greater for blacks, Hispanics, and foreign language speakers. CONCLUSIONS: The spring 2009 influenza A H1N1 outbreak disproportionately affected children, young adults, and racial and ethnic minorities. Opportunities exist to improve the timeliness of antiviral treatment. Potential barriers to care for racial and ethnic minorities should be proactively addressed to ensure prompt evaluation and treatment.

Maternal, delivery, and perinatal characteristics associated with cryptorchidism: a population-based case-control study among births in Washington State.

BACKGROUND: The etiology of cryptorchidism is largely unknown. To identify maternal, perinatal, and delivery characteristics associated with cryptorchidism at birth, we conducted a population-based case-control study using Washington State birth certificates linked to birth hospitalization records. METHODS: We identified 2,395 cases of cryptorchidism among male infants born in Washington State during 1986-1996, and, for comparison, we randomly selected four controls per case (N = 9,580), frequency-matched by year of birth. RESULTS: Infant characteristics associated with cryptorchidism included low birth weight (OR = 1.5; 95% CI = 1.3-1.8), small size for gestational age (OR = 1.9; 95% CI = 1.6-2.2), and breech presentation (OR = 1.7; 95% CI = 1.4-2.1). In addition to cryptorchidism, cases were more likely to have another type of congenital malformation (OR = 3.7; 95% CI = 3.2-4.2), particularly digestive (OR = 6.8; 95% CI = 3.7-12.7) or genitourinary (OR = 4.1; 95% CI = 3.0-5.6). Maternal and pregnancy characteristics associated with cryptorchidism included nulliparity (OR = 1.2; 95% CI = 1.1-1.3), maternal smoking during pregnancy (OR = 1.2; 95% CI = 1.1-1.4), and the following pregnancy complications: oligohydramnios (OR = 1.8; 95% CI = 1.3-2.6), placental abnormality (OR = 1.3; 95% CI = 1.0-1.8), and pregnancy-induced hypertension (OR = 1.6; 95% CI = 1.4-1.9). Odds ratios were similar when the analysis was restricted to term infants. CONCLUSIONS: These findings suggest that factors affecting fetal growth and development may increase the risk of cryptorchidism.