Neural tube defects: epidemiology, detection, and prevention

Routine Ultrasonography Compared With Maternal Serum Alpha-fetoprotein for Neural Tube Defect Screening

OBJECTIVE

This study was done to estimate the value of prenatal maternal serum alpha-fetoprotein (MSAFP) screening compared with that of routine ultrasonography in the diagnosis of neural tube defects (NTDs).

METHODS

An integrated database was used retrospectively to identify cases of NTDs among 219,000 consecutive pregnancy outcomes observed during a 7-year period at 40 Kaiser Permanente facilities in Northern California. We specifically examined types of NTD and the tests used to diagnose cases.

RESULTS

We identified 189 NTD cases, 102 of which had received MSAFP screening. Results of MSAFP testing were negative in 25 (25%) of these 102 cases. Without other testing, these 25 NTD diagnoses would have been missed. These included 15 (38%) of the 40 spina bifida cases screened, 6 (67%) of the 9 encephalocele cases screened, and 4 (8%) of the 53 anencephaly cases screened. Of the 186 NTD cases diagnosed prenatally, 115 (62%) were initially detected by routine ultrasonography administered during the second trimester without knowledge of MSAFP values; 69 (37%) were diagnosed by targeted ultrasonography after MSAFP screening indicated a higher risk for NTD; and 2 (1%) were diagnosed by pathology examination after miscarriage.

CONCLUSION

Compared with MSAFP performed alone for screening, routine second-trimester ultrasonography was more likely to discover an NTD.

Neural tube defects after infertility treatment: a review

OBJECTIVE

To investigate whether an association exists between ovulation induction and neural tube defects (NTDs).

MATERIALS AND METHODS

Risk estimations in the medical literature were identified through Medline, and validity and power were assessed. Large in vitro fertilization-embryo transfer (IVF-ET) registries represent another source of information. The total number of NTDs and the total number of fetuses were computed from five registries. These data were expressed as proportions and compared with data from the general population.

RESULTS

Only one study could be identified as both valid and powerful, through literature review. This case-control study concluded there was no association between ovulation induction and NTDs. The pool of IVF-ET registry data represents another powerful epidemiologic tool. Analysis of the registry data confirms the findings of the case-control study.

CONCLUSIONS

Ovulation induction does not seem to represent a risk factor for NTDs in the offspring.