Chemicals, birth defects and stillbirths in New Brunswick: associations with agricultural activity.
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We describe a series of investigations that were conducted in support of the Task Force on Chemicals in the Environment and Human Reproductive Problems in New Brunswick. Geographic and temporal analyses and case-control studies, with the use of vital statistics, hospital records, the Canadian Congenital Anomalies Surveillance System and chemical databases, revealed no association between pesticides used in forestry and reproductive problems. Evidence of an association between the potential exposure to agricultural chemicals and three major anomalies combined as well as spina bifida without hydrocephalus was found. More plausible was an association between stillbirths and such exposure during the second trimester of pregnancy. This finding, along with the cyclic patterns of stillbirth in the agricultural Saint John River basin and the somewhat higher stillbirth rates in New Brunswick than in adjacent provinces or in Canada as a whole, suggests that further attention should focus on possible associations between agricultural activity and stillbirths. (+info)
Birth prevalence and recurrence rates of neural tube defects in southern Alberta in 1970-81.
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Given the observed variation in birth prevalence and recurrence rates of neural tube defects, it is important to obtain such data specific to a given locality for research and genetic counseling purposes. A review of hospital medical charts, the patient lists of the Medical Genetics and Myelomeningocele clinics at Alberta Children's Hospital and data from the Canadian Congenital Anomalies Surveillance System revealed the annual birth prevalence rate of neural tube defects in southern Alberta in 1970-81 to be 1.62/1000 total births. This figure suggests southern Alberta to be a low-frequency area. There was no significant variation in the annual rates of spina bifida, encephalocele or all neural tube defects combined over the study period. A significant linear decline in the frequency of births of anencephalic infants, however, was noted (p = 0.025). Information on the total reproductive history of the mothers revealed that the empiric risk of recurrence of a neural tube defect was 2.2%, and the risk to all siblings was estimated to be 2.3%. In future prevalence studies multiple sources of case ascertainment should be used, including data on pregnancies terminated because of a fetal neural tube defect. (+info)
A family showing apparent X linked inheritance of both anencephaly and spina bifida.
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A family is reported which includes five males, two with spina bifida, two sibs with anencephaly, and one with both high and low spinal lesions. The affected subjects came from four sibships in three generations. The mode of inheritance of these neural tube defects is consistent with X linkage. (+info)
Spina bifida and anencephaly: are miscarriages a possible cause?
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The marriage-to-conception interval in 151 pregnancies producing infants with anencephaly or spina bifida was not significantly different from that in 218 pregnancies resulting in normal infants. Significantly more miscarriages occurred before than after the birth of 285 infants with anencephaly or spina bifida, but in 133 controls no before-after difference was observed. These observations seem to favour the idea that miscarriages are a manifestation rather than a cause of anencephaly and spina bifida. (+info)
Prevalence and prenatal diagnosis of neural tube defects in Nova Scotia in 1980-84.
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A survey of the records of all hospitals with obstetric services in Nova Scotia revealed that during 1980-84 there were 122 pregnancies involving a neural tube defect. The mean rate was 2/1000 births. Of the affected fetuses or infants 54% had spina bifida, 35% had anencephaly and 11% had encephalocele. The records showed that in the early part of the period studied at least one prenatal ultrasonographic examination had been performed in 60% of the pregnancies; in 1984 the rate was 74%. When examinations done before 16 weeks' gestation were excluded, the overall detection rates at the first ultrasonographic examination were 100% for anencephaly and 73% for spina bifida and encephalocele; the rates improved toward the end of the study period. (+info)
Neural-tube defects: importance of a history of abortion in aetiology.
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The overall incidence of anencephaly and spina bifida (ASB) in 69,056 pregnancies was 4.7/1000 births. ASB was more common (8.4/1000 births) among children of mothers who had had two or more abortions, but the increased risk was confined to spina bifida. A history of abortion was more common in older women and women of higher parity, but this was not matched by a similar increase in the incidence of ASB. The incidence of ASB was related to social class, but the prevalence of previous abortions was similar in all classes. The results suggest that expectant mothers with a history of two or more abortions have an increased risk of producing a child with spina bifida. The abortions are considered to be a manifestation of previous abnormal conceptions rather than the primary cause. (+info)
Contrasting effects of maternal fertility and birth rank on the occurrence of neural tube defects.
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The relationships between the occurrence of anencephalus and spina bifida, sibship size and birth rank were examined, using linked records for births in British Columbia. Comparison of 414 sibships in which at least one infant had a neural tube defect with 1362 randomly chosen unaffected sibships showed that the affected sibships were larger. There were both more births than expected after the affected birth, and shorter intervals between births before the affected birth. Within sibships, the risk of anencephalus or spina bifida decreased strongly with increasing birth rank. No associations were seen with maternal age at first birth. (+info)
Sib risk of neural tube defect: is prenatal diagnosis indicated in pregnancies following the birth of a hydrocephalic child?
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Recurrence frequencies of central nervous system malformations in sibs of probands with anencephalus or spina bifida range between 1% and 7%. The frequency of hydrocephalus among sibs of such probands is low (0.21%) but, nevertheless, is increased 2 to 5-fold when compared to general population frequencies. Anencephalus and spina bifida cystica were observed in 1.65% of sibs of children with hydrocephalus, a 2- to 8-fold increased over the population frequencies. These data indicate that some aetiological factors may be common to all three malformations. The risk figure of 1.65% for anencephalus and spina bifida in sibs born after the birth of a hydrocephalic proband constitutes sufficient indication for prenatal diagnosis by alphafetoprotein determination of the amniotic fluid. (+info)