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Associated malformations in infants and fetuses with upper or lower neural tube defects
Insights
Neural tube defects show varying associated malformations depending on location and infant versus fetus status. Upper neural tube defects may warrant separate epidemiological consideration from lower ones.
Area of Science:
- Medical Genetics
- Developmental Biology
- Public Health Epidemiology
Background:
- Neural tube defects (NTDs) are a significant group of congenital anomalies.
- Understanding associated malformations is crucial for diagnosis and etiology.
- Previous studies have not consistently differentiated NTDs by level or outcome (live birth vs. termination).
Purpose of the Study:
- To investigate and compare associated non-neural malformations in infants and aborted fetuses with NTDs.
- To determine if the level of the NTD (upper vs. lower) influences associated malformations.
- To explore potential reasons for differences in malformation patterns between live-born infants and aborted fetuses.
Main Methods:
- Analysis of data from three large malformation registers.
- Inclusion of live-born infants with NTDs (N=3,809) and aborted fetuses with NTDs (N=748).
- Comparison of associated malformation frequencies based on NTD type, level, and outcome.
Main Results:
- Upper spina bifida and encephalocele were more frequently associated with non-neural malformations in infants compared to anencephaly or lower spina bifida.
- Aborted fetuses with spina bifida or encephalocele showed higher rates of associated malformations than infants with these NTDs.
- Anencephaly showed the opposite pattern, with higher associated malformation rates in infants than in aborted fetuses.
Conclusions:
- Differences in malformation patterns may be influenced by diagnostic detail, prenatal detection biases, and spontaneous abortion rates.
- The type of associated malformation varies with the NTD level, suggesting potentially different causal mechanisms or developmental timing.
- Upper and lower NTDs may have distinct epidemiological significance and should be analyzed separately, particularly regarding associated limb defects.
Abstract:
The paper describes associated malformations in infants born with neural tube defects (N = 3,809) from three large malformation registers and in fetuses aborted because of a diagnosed neural tube defect (N = 748) from two of the registers. In infants, upper spina bifida and encephalocele are more often associated with non-neural malformations than anencephaly or lower spina bifida. Aborted fetuses with spina bifida or encephalocele have associated malformations registered more often than infants with those neural tube defects, but the opposite is true for anencephaly. The degree of detail of the investigation of an aborted specimen or a perinatally dead infant will contribute to such differences but they can also depend on the fact that prenatal detection may be facilitated by the simultaneous presence of other malformations like body wall defects. Also, fetuses with many malformations may be more prone to abort spontaneously late in pregnancy. Variable prenatal diagnosis may, therefore, explain population differences in the pattern of associated malformations. The type of associated malformation differs with the level of the neural tube defect: this could be due to different causal mechanisms or be a question of cranio-caudal level and/or timing. For limb reduction defects, however, we did not find any association between upper limb and upper neural tube defects or lower limb and lower neural tube defects. These findings together with other epidemiological data support the idea that upper and lower neural tube defects may have different significance in epidemiological studies and should be treated separately.