Hypospadias Prevalence and Trends in International Birth Defect Surveillance Systems, 1980-2010.

BACKGROUND: Hypospadias is a common male birth defect that has shown widespread variation in reported prevalence estimates. Many countries have reported increasing trends over recent decades. OBJECTIVE: To analyze the prevalence and trends of hypospadias for 27 international programs over a 31-yr period. DESIGN, SETTING, AND PARTICIPANTS: The study population included live births, stillbirths, and elective terminations of pregnancy diagnosed with hypospadias during 1980-2010 from 27 surveillance programs around the world. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: We used joinpoint regression to analyze changes over time in international total prevalence of hypospadias across programs, prevalence for each specific program, and prevalence across different degrees of severity of hypospadias. RESULTS AND LIMITATIONS: The international total prevalence of hypospadias for all years was 20.9 (95% confidence interval: 19.2-22.6) per 10000 births. The prevalence for each program ranged from 2.1 to 39.1 per 10000 births. The international total prevalence increased 1.6 times during the study period, by 0.25 cases per 10000 births per year (p<0.05). When analyzed separately, there were increasing trends for first-, second-, and third-degree hypospadias during the early 1990s to mid-2000s. The majority of programs (61.9%) had a significantly increasing trend during many of the years evaluated. Limitations include known differences in data collection methods across programs. CONCLUSIONS: Although there have been changes in clinical practice and registry ascertainment over time in some countries, the consistency in the observed increasing trends across many programs and by degrees of severity suggests that the total prevalence of hypospadias may be increasing in many countries. This observation is contrary to some previous reports that suggested that the total prevalence of hypospadias was no longer increasing in recent decades. PATIENT SUMMARY: We report on the prevalence and trends of hypospadias among 27 birth defect surveillance systems, which indicate that the prevalence of hypospadias continues to increase internationally.

An International Comparison of Death Classification at 22 to 25 Weeks' Gestational Age.

OBJECTIVES: To explore international differences in the classification of births at extremely low gestation and the subsequent impact on the calculation of survival rates. METHODS: We used national data on births at 22 to 25 weeks' gestation from the United States (2014; n = 11 144), Canada (2009-2014; n = 5668), the United Kingdom (2014-2015; n = 2992), Norway (2010-2014; n = 409), Finland (2010-2015; n = 348), Sweden (2011-2014; n = 489), and Japan (2014-2015; n = 2288) to compare neonatal survival rates using different denominators: all births, births alive at the onset of labor, live births, live births surviving to 1 hour, and live births surviving to 24 hours. RESULTS: For births at 22 weeks' gestation, neonatal survival rates for which we used live births as the denominator varied from 3.7% to 56.7% among the 7 countries. This variation decreased when the denominator was changed to include stillbirths (ie, all births [1.8%-22.3%] and fetuses alive at the onset of labor [3.7%-38.2%]) or exclude early deaths and limited to births surviving at least 12 hours (50.0%-77.8%). Similar trends were seen for infants born at 23 weeks' gestation. Variation diminished considerably at 24 and 25 weeks' gestation. CONCLUSIONS: International variation in neonatal survival rates at 22 to 23 weeks' gestation diminished considerably when including stillbirths in the denominator, revealing the variation arises in part from differences in the proportion of births reported as live births, which itself is closely connected to the provision of active care.

International variations in the gestational age distribution of births: an ecological study in 34 high-income countries.

Background: Few studies have investigated international variations in the gestational age (GA) distribution of births. While preterm births (22-36 weeks GA) and early term births (37-38 weeks) are at greater risk of adverse health outcomes compared to full term births (39-40 weeks), it is not known if countries with high preterm birth rates also have high early term birth rates. We examined rate associations between preterm and early term births and mean term GA by mode of delivery onset. Methods: We used routine aggregate data on the GA distribution of singleton live births from up to 34 high-income countries/regions in 1996, 2000, 2004, 2008 and 2010 to study preterm and early term births overall and by spontaneous or indicated onset. Pearson correlation coefficients were adjusted for clustering in time trend analyses. Results: Preterm and early term births ranged from 4.1% to 8.2% (median 5.5%) and 15.6% to 30.8% (median 22.2%) of live births in 2010, respectively. Countries with higher preterm birth rates in 2004-2010 had higher early term birth rates (r > 0.50, P < 0.01) and changes over time were strongly correlated overall (adjusted-r = 0.55, P < 0.01) and by mode of onset. Conclusion: Positive associations between preterm and early term birth rates suggest that common risk factors could underpin shifts in the GA distribution. Targeting modifiable population risk factors for delivery before 39 weeks GA may provide a useful preterm birth prevention paradigm.

Temporal Trends in Late Preterm and Early Term Birth Rates in 6 High-Income Countries in North America and Europe and Association With Clinician-Initiated Obstetric Interventions.

IMPORTANCE: Clinicians have been urged to delay the use of obstetric interventions (eg, labor induction, cesarean delivery) until 39 weeks or later in the absence of maternal or fetal indications for intervention. OBJECTIVE: To describe recent trends in late preterm and early term birth rates in 6 high-income countries and assess association with use of clinician-initiated obstetric interventions. DESIGN: Retrospective analysis of singleton live births from 2006 to the latest available year (ranging from 2010 to 2015) in Canada, Denmark, Finland, Norway, Sweden, and the United States. EXPOSURES: Use of clinician-initiated obstetric intervention (either labor induction or prelabor cesarean delivery) during delivery. MAIN OUTCOMES AND MEASURES: Annual country-specific late preterm (34-36 weeks) and early term (37-38 weeks) birth rates. RESULTS: The study population included 2,415,432 Canadian births in 2006-2014 (4.8% late preterm; 25.3% early term); 305,947 Danish births in 2006-2010 (3.6% late preterm; 18.8% early term); 571,937 Finnish births in 2006-2015 (3.3% late preterm; 16.8% early term); 468,954 Norwegian births in 2006-2013 (3.8% late preterm; 17.2% early term); 737,754 Swedish births in 2006-2012 (3.6% late preterm; 18.7% early term); and 25,788,558 US births in 2006-2014 (6.0% late preterm; 26.9% early term). Late preterm birth rates decreased in Norway (3.9% to 3.5%) and the United States (6.8% to 5.7%). Early term birth rates decreased in Norway (17.6% to 16.8%), Sweden (19.4% to 18.5%), and the United States (30.2% to 24.4%). In the United States, early term birth rates decreased from 33.0% in 2006 to 21.1% in 2014 among births with clinician-initiated obstetric intervention, and from 29.7% in 2006 to 27.1% in 2014 among births without clinician-initiated obstetric intervention. Rates of clinician-initiated obstetric intervention increased among late preterm births in Canada (28.0% to 37.9%), Denmark (22.2% to 25.0%), and Finland (25.1% to 38.5%), and among early term births in Denmark (38.4% to 43.8%) and Finland (29.8% to 40.1%). CONCLUSIONS AND RELEVANCE: Between 2006 and 2014, late preterm and early term birth rates decreased in the United States, and an association was observed between early term birth rates and decreasing clinician-initiated obstetric interventions. Late preterm births also decreased in Norway, and early term births decreased in Norway and Sweden. Clinician-initiated obstetric interventions increased in some countries but no association was found with rates of late preterm or early term birth.

Differences in perinatal and infant mortality in high-income countries: artifacts of birth registration or evidence of true differences?

BACKGROUND: Variation in birth registration criteria may compromise international comparisons of fetal and infant mortality. We examined the effect of birth registration practices on fetal and infant mortality rates to determine whether observed differences in perinatal and infant mortality rates were artifacts of birth registration or reflected true differences in health status. METHODS: A retrospective population-based cohort study was done using data from Canada, United States, Denmark, Finland, Iceland, Norway, and Sweden from 1995-2005. Main outcome measures included live births by gestational age and birth weight; gestational age-and birth weight-specific stillbirth rates; neonatal, post-neonatal, and cause-specific infant mortality. RESULTS: Proportion of live births <22 weeks varied substantially: Sweden (not reported), Iceland (0.00%), Finland (0.001%), Denmark (0.01%), Norway (0.02%), Canada (0.07%) and United States (0.08%). At 22-23 weeks, neonatal mortality rates were highest in Canada (892.2 per 1000 live births), Denmark (879.3) and Iceland (1000.0), moderately high in the United States (724.1), Finland (794.3) and Norway (739.0) and low in Sweden (561.2). Stillbirth:live birth ratios at 22-23 weeks were significantly lower in the United States (79.2 stillbirths per 100 live births) and Finland (90.8) than in Canada (112.1), Iceland (176.2) and Norway (173.9). Crude neonatal mortality rates were 83% higher in Canada and 96% higher in the United States than Finland. Neonatal mortality rates among live births ≥ 28 weeks were lower in Canada and United States compared with Finland. Post-neonatal mortality rates were higher in Canada and United States than in Nordic countries. CONCLUSIONS: Live birth frequencies and stillbirth and neonatal mortality patterns at the borderline of viability are likely due to differences in birth registration practices, although true differences in maternal, fetal and infant health cannot be ruled out. This study emphasises the need for further standardisations, in order to enhance the relevance of international comparisons of infant mortality.

Incidence, risk factors, and consequences of amniotic fluid embolism.

BACKGROUND: Amniotic fluid embolism (AFE) is a rare but serious cause of maternal mortality whose aetiology remains obscure. Previous population-based studies have reported associations with labour induction and caesarean delivery. METHODS: We updated a previous analysis based on the US Nationwide Inpatient Sample from 1999 to 2008. We adapted a diagnostic validation algorithm to minimise false-positive diagnoses, along with statistical methods that account for the stratified random sampling design. RESULTS: Of the 8 571 209 deliveries recorded in the database, 276 met our case definition of AFE, of which 62 (22.9% of the 274 with known vital status) were fatal. Significant associations with AFE were observed for medical induction {adjusted odds ratio [aOR] = 1.7 [95% confidence interval (CI) 1.2, 2.5]}, caesarean delivery [aOR = 15.0; 95% CI 9.4, 23.9], instrumental vaginal delivery [aOR = 6.6; 95% CI 4.0, 11.1], and cervical/uterine trauma [aOR = 7.4; 95% CI 3.6, 14.9]. AFE was associated with increases in risk of stillbirth, hysterectomy, maternal death, and prolonged maternal length of delivery hospital stay. CONCLUSIONS: AFE remains an extremely serious obstetric complication with high risks of maternal and fetal mortality. The increased risks of AFE associated with labour induction and caesarean delivery have implications for elective use of these interventions.

Association between maternal chronic conditions and congenital heart defects: a population-based cohort study.

BACKGROUND: This study quantifies the association between maternal medical conditions/illnesses and congenital heart defects (CHDs) among infants. METHODS AND RESULTS: We carried out a population-based study of all mother-infant pairs (n=2,278,838) in Canada (excluding Quebec) from 2002 to 2010 using data from the Canadian Institute for Health Information. CHDs among infants were classified phenotypically through a hierarchical grouping of International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Canada codes. Maternal conditions such as multifetal pregnancy, diabetes mellitus, hypertension, and congenital heart disease were defined by use of diagnosis codes. The association between maternal conditions and CHDs and its subtypes was modeled using logistic regression with adjustment for maternal age, parity, residence, and other factors. There were 26 488 infants diagnosed with CHDs at birth or at rehospitalization in infancy; the overall CHD prevalence was 116.2 per 10,000 live births, of which the severe CHD rate was 22.3 per 10,000. Risk factors for CHD included maternal age ≥40 years (adjusted odds ratio [aOR], 1.48; 95% confidence interval [CI], 1.39-1.58), multifetal pregnancy (aOR, 4.53; 95% CI, 4.28-4.80), diabetes mellitus (type 1: aOR, 4.65; 95% CI, 4.13-5.24; type 2: aOR, 4.12; 95% CI, 3.69-4.60), hypertension (aOR, 1.81; 95% CI, 1.61-2.03), thyroid disorders (aOR, 1.45; 95% CI, 1.26-1.67), congenital heart disease (aOR, 9.92; 95% CI, 8.36-11.8), systemic connective tissue disorders (aOR, 3.01; 95% CI, 2.23-4.06), and epilepsy and mood disorders (aOR, 1.41; 95% CI, 1.16-1.72). Specific CHD subtypes were associated with different maternal risk factors. CONCLUSIONS: Several chronic maternal medical conditions, including diabetes mellitus, hypertension, connective tissue disorders, and congenital heart disease, confer an increased risk of CHD in the offspring.

Incidence, risk factors, and temporal trends in severe postpartum hemorrhage.

OBJECTIVE: Because the diagnosis of postpartum hemorrhage (PPH) depends on the accoucheur's subjective estimate of blood loss and varies according to mode of delivery, we examined temporal trends in severe PPH, defined as PPH plus receipt of a blood transfusion, hysterectomy, and/or surgical repair of the uterus. STUDY DESIGN: We analyzed 8.5 million hospital deliveries in the US Nationwide Inpatient Sample from 1999 to 2008 for temporal trends in, and risk factors for, severe PPH, based on International Classification of Diseases, 9th revision, clinical modification diagnosis and procedure codes. Sequential logistic regression models that account for the stratified random sampling design were used to assess the extent to which changes in risk factors explain the trend in severe PPH. RESULTS: Of the total 8,571,209 deliveries, 25,906 (3.0 per 1000) were complicated by severe PPH. The rate rose from 1.9 to 4.2 per 1000 from 1999 to 2008 (P for yearly trend < .0001), with increases in severe atonic and nonatonic PPH, due especially to PPH with transfusion, but also PPH with hysterectomy. Significant risk factors included maternal age ≥35 years (adjusted odds ratio [aOR], 1.5; 95% confidence interval [CI], 1.5-1.6), multiple pregnancy (aOR, 2.8; 95% CI, 2.6-3.0), fibroids (aOR, 2.0; 95% CI, 1.8-2.2), preeclampsia (aOR, 3.1; 95% CI, 2.9-3.3), amnionitis (aOR, 2.9; 95% CI, 2.5-3.4), placenta previa or abruption (aOR, 7.0; 95% CI, 6.6-7.3), cervical laceration (aOR, 94.0; 95% CI, 87.3-101.2), uterine rupture (aOR, 11.6; 95% CI, 9.7-13.8), instrumental vaginal delivery (aOR, 1.5; 95% CI, 1.4-1.6), and cesarean delivery (aOR, 1.4; 95% CI, 1.3-1.5). Changes in risk factors, however, accounted for only 5.6% of the increase in severe PPH. CONCLUSION: A doubling in incidence of severe PPH over 10 years was not explained by contemporaneous changes in studied risk factors.

Influence of definition based versus pragmatic birth registration on international comparisons of perinatal and infant mortality: population based retrospective study.

OBJECTIVES: To examine variations in the registration of extremely low birthweight and early gestation births and to assess their effect on perinatal and infant mortality rankings of industrialised countries. DESIGN: Retrospective population based study. SETTING: Australia, Canada, European countries, and the United States for 2004; Australia, Canada, and New Zealand for 2007. POPULATION: National data on live births and on fetal, neonatal, and infant deaths. MAIN OUTCOME MEASURES: Reported proportions of live births with birth weight/gestational age of less than 500 g, less than 1000 g, less than 24 weeks, and less than 28 weeks; crude rates of fetal, neonatal, and infant mortality; mortality rates calculated after exclusion of births under 500 g, under 1000 g, less than 24 weeks, and less than 28 weeks. RESULTS: The proportion of live births under 500 g varied widely from less than 1 per 10,000 live births in Belgium and Ireland to 10.8 per 10,000 live births in Canada and 16.9 in the United States. Neonatal deaths under 500 g, as a proportion of all neonatal deaths, also ranged from less than 1% in countries such as Luxembourg and Malta to 29.6% in Canada and 31.1% in the United States. Rankings of countries based on crude fetal, neonatal, and infant mortality rates differed substantially from rankings based on rates calculated after exclusion of births with a birth weight of less than 1000 g or a gestational age of less than 28 weeks. CONCLUSIONS: International differences in reported rates of extremely low birthweight and very early gestation births probably reflect variations in registration of births and compromise the validity of international rankings of perinatal and infant mortality.

Temporal trends in maternal mortality in Canada I: estimates based on vital statistics data.

OBJECTIVES: Vital Statistics and World Health Organization reports show a recent increase in maternal mortality in Canada. We carried out a study of temporal trends, regional variations, and causes of death in Canadian maternal mortality using Vital Statistics data. METHODS: We used Vital Statistics death registrations to ascertain maternal deaths between 1981 and 2007. Maternal mortality rates, risk ratios, and 95% confidence intervals were estimated, and the Cochran-Armitage test was used to evaluate temporal trends. We used hospitalization data from the Canadian Institute for Health Information from 1996 to 2007 to confirm maternal mortality trends observed in the Vital Statistics data. RESULTS: Maternal mortality rates increased significantly from 4.5 (95% CI 3.3 to 5.8) in 1981 to 1983 to 4.7 (95% CI 3.5 to 6.2) in 1996 to 1998 and to 7.2 (95% CI 5.7 to 9.0) per 100 000 live births in 2005 to 2007 (P value for trend < 0.001). The most common causes of maternal death were diseases of the circulatory system, obstetric embolism (venous thromboembolism and amniotic fluid embolism), and hypertension. Deaths due to diseases of the circulatory system and puerperal infection increased significantly from 1981 to 2007. Maternal mortality rates in the hospitalization data were higher and did not show an increase over time. Provincial and territorial maternal mortality rates from Vital Statistics data showed varying degrees of under-ascertainment (12% to 70%) compared with hospitalization data. CONCLUSION: Temporal increases in maternal mortality in Canada observed in Vital Statistics data do not correspond with stable temporal trends observed in hospitalization data, and appear to be an artefact of changes in the coding and ascertainment of maternal deaths.

Severe maternal morbidity in Canada, 2003 to 2007: surveillance using routine hospitalization data and ICD-10CA codes.

OBJECTIVE: To examine the feasibility of using routine labour and delivery hospitalization data and international classification of diseases (ICD-10CA) codes for carrying out surveillance of severe maternal morbidity in Canada. METHODS: We identified ICD-10CA diagnosis codes and Canadian Classification of Interventions (CCI) procedure codes associated with severe maternal illness. Severe maternal morbidity rates in Canada (excluding Quebec) for the period 2003 to 2007 were estimated using the Discharge Abstract Database of the Canadian Institute for Health Information. Rates were compared across maternal age, parity, plurality, labour induction, delivery by Caesarean section, and other factors. Case fatality rates and length of hospitalization were also estimated. RESULTS: Among the 1 336 356 women who delivered between 2003 and 2007, the rate of severe maternal morbidity was 13.8 per 1000 deliveries. The mean length of hospital stay for women with and without a severe illness was 5.4 days vs. 2.5 days, while the frequency of prolonged hospital stay (>or=7 days) was 19.8% vs. 1.8%, respectively (rate ratio 9.3; 95% CI 9.0 to 9.6). Case fatality rates differed significantly between women with and without a severe illness at 2.98 vs. 0.008 per 1000, respectively (rate ratio 392.8; 95% CI 200.3 to 700.4). Rates of severe maternal morbidity were higher among deliveries to older and nulliparous women and to those delivering twins or triplets. CONCLUSION: Disease frequency, case fatality, and length of hospitalization patterns suggest that comprehensive and timely surveillance of severe maternal morbidity in Canada is feasible using the Canadian Institute for Health Information hospitalization data and ICD-10CA/CCI codes.

Epidemiology of pregnancy-associated venous thromboembolism: a population-based study in Canada.

OBJECTIVE: To estimate the frequency of, and to identify risk factors for, pregnancy-associated venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE) requiring hospitalization. METHODS: We conducted a population-based cohort study (N = 3 852 569) using the Discharge Abstract Database of the Canadian Institute for Health Information (CIHI), for the fiscal years 1991-1992 to 2005-2006. All women with pregnancy-related hospitalizations in Canada (excluding Quebec and Manitoba) were identified. DVT and PE rates were calculated using the number of hospital deliveries (i.e., cohort of women at risk) as the denominator for the antepartum and peripartum (labour and delivery) hospitalizations and for postpartum readmissions. Risk factors for DVT/PE were identified using logistic regression. RESULTS: During the antepartum, peripartum, and postpartum periods, 5.4, 7.2, and 4.3 VTE cases per 10,000 pregnancies, respectively were observed. The total incidence of DVT was 12.1 per 10,000 pregnancies (0.26 deaths per 100,000), and the rate for PE was 5.4 per 10,000 (0.96 deaths per 100,000). The strongest risk factors for DVT occurrence during the peripartum period were thrombophilia (adjusted odds ratio [aOR] 15.4; 95% CI 10.8-22.0), a past history of circulatory disease, and major puerperal infection, whereas those for PE were previous DVT (aOR 56.9; 95% CI 40.9-79.1), heart disease (aOR 43.4, 95% CI 35.0-53.9), antiphospholipid syndrome, past history of circulatory disease, transfusion, and major puerperal infection. CONCLUSION: Cases of VTE and associated deaths occur most frequently during the peripartum period. Although mortality from pregnancy-associated VTE is low, maternal characteristics and other factors can be used to identify women at risk for VTE.

Amniotic-fluid embolism and medical induction of labour: a retrospective, population-based cohort study.

BACKGROUND: Amniotic-fluid embolism is a rare, but serious and often fatal maternal complication of delivery, of which the cause is unknown. We undertook an epidemiological study to investigate the association between amniotic-fluid embolism and medical induction of labour. METHODS: We used a population-based cohort of 3 million hospital deliveries in Canada between 1991 and 2002 to assess the associations between overall and fatal rates of amniotic-fluid embolism and medical and surgical induction, maternal age, fetal presentation, mode of delivery, and pregnancy and labour complications. FINDINGS: Total rate of amniotic-fluid embolism was 14.8 per 100,000 multiple-birth deliveries and 6.0 per 100,000 singleton deliveries (odds ratio 2.5 [95% CI 0.9-6.2]). Of the 180 cases of amniotic-fluid embolism in women with singleton deliveries during the study period, 24 (13%) were fatal. We saw no significant temporal increase in occurrence of amniotic-fluid embolism for total or fatal cases. Medical induction of labour nearly doubled the risk of overall cases of amniotic-fluid embolism (adjusted odds ratio 1.8 [1.3-2.7]), and the association was stronger for fatal cases (crude odds ratio 3.5 [1.5-8.4]). Maternal age of 35 years or older, caesarean or instrumental vaginal delivery, polyhydramnios, cervical laceration or uterine rupture, placenta previa or abruption, eclampsia, and fetal distress were also associated with an increased risk. INTERPRETATION: Medical induction of labour seems to increase the risk of amniotic-fluid embolism. Although the absolute excess risk is low, women and physicians should be aware of this risk when making decisions about elective labour induction.

Anophthalmia and microphthalmia in the Alberta Congenital Anomalies Surveillance System.

BACKGROUND: A higher than expected rate of anophthalmia/microphthalmia (A/M) for 1999 was noted in both the Alberta Congenital Anomalies Surveillance System (ACASS) and the Canadian Congenital Anomalies Surveillance System (CCASS). Since this increase was at variance with the previous 19 years, we performed a review to determine whether the increase was true and, if so, the possible explanation. METHODS: We reviewed the records of the cases of A/M in the ACASS together with the accompanying attachments (e.g., consultant, autopsy and chromosome reports) for 1991-2001. In addition, we contacted all 91 registered ophthalmologists in Alberta. Letters were also written to the Edmonton and Calgary offices of the Canadian National Institute for the Blind (CNIB). RESULTS: Sixty cases of A/M were ascertained over the study period. Of the 88 active ophthalmologists in the province, 21 (24%) replied, but no new cases were ascertained from this source. No replies were received from the CNIB. We constructed five categories of clinical phenotypes for the 60 cases: 20 had a chromosomal etiology, 13 had a recognized syndrome or association, 16 had extraocular malformations, 5 had other eye anomalies, and 6 had A/M only. Pregnancy terminations were not included. The higher rate in 1999 was mainly due to cases with a chromosomal etiology or a recognized syndrome or association. There was no indication that a teratogen was causing a cluster of A/M cases, as our annual rates were comparable to those for other jurisdictions not only in Canada but also in other countries. INTERPRETATION: Our review confirmed that the rate of A/M in Alberta in 1999 was high but that the increase was mainly due to five cases of trisomy 13 together with one case associated with a syndrome (Meckel-Gruber). Our findings provide reassurance that there was no environmental cause of clustering of anophthalmia or microphthalmia. This review demonstrates the importance of ongoing population-based surveillance in providing baseline birth prevalence rates for evaluating trends and clusters.

Incidence of neural tube defects in Ontario, 1986-1999.

BACKGROUND: Prenatal screening and the promotion of folic acid intake could affect the incidence of neural tube defects (NTDs). We examined trends in the total NTD incidence, as detected in live births, stillbirths and therapeutic abortions, from 1986 to 1999 in Ontario. METHODS: To capture cases of NTDs we used data from the Canadian Congenital Anomalies Surveillance System and hospital data on therapeutic abortions. We calculated the total incidence of NTDs by combining the numbers of NTDs occurring in live births, stillbirths and therapeutic abortions. RESULTS: The total NTD incidence rate increased from 11.7 per 10,000 pregnancies in 1986 to 16.2 per 10,000 in 1995, and it subsequently decreased to 8.6 per 10,000 by 1999. The NTD birth rate (live births and stillbirths) decreased from 10.6 per 10,000 births in 1986 to 5.3 per 10,000 in 1999. The rate of therapeutic abortions with an NTD or hydrocephalus rose from 17.5 per 10,000 abortions in 1986 to 50.7 per 10,000 in 1995 and fell to 28.7 per 10,000 abortions in 1999. INTERPRETATION: The total NTD incidence rate increased from 1986 to 1995, probably because of increased prenatal screening and better detection of NTDs. The decline from 1995 to 1999 may have been due to increased folic acid intake among women at the time of conception.