Neural-tube defects: importance of a history of abortion in aetiology

Determinants of neural tube defect among newborns admitted to neonatal intensive care units of teaching hospitals in Gedeo Zone and Sidama Region, Southern Ethiopia: a case-control study

BACKGROUND

Neural tube defects are a significant cause of morbidity and mortality that can occur in the early pregnancy periods. Though the burden is high, it gains only limited attention. In Ethiopia, the estimated number of neural tube defect cases was significantly higher. So, identifying factors contributing to it would be significant for planning risk reduction and preventive strategies. Therefore, identifying the possible determinants was aimed at this study.

METHODS

A hospital-based, unmatched case-control study was conducted on 104 cases and 208 controls selected from neonatal intensive care units of teaching hospitals in Gedeo Zone and Sidama Region, southern Ethiopia from December 2021 to November 2022. All neural tube defect cases were included consecutively and controls were selected by using a simple random sampling method. Data were collected using interviewer-administered semistructured questionnaires. Data analysis was done by using SPSS V.25. Binary logistic regression was used, and variables with a p value less than 0.25 in bivariate analysis were entered into the multivariable logistic regression model. An adjusted OR with a 95% CI was estimated, and finally, variables that show a level of p value less than 0.05 in multivariable analysis were declared statistically significant.

RESULT

After controlling confounders, factors such as unplanned pregnancy 2.20 (95% CI 1.20 to 4.041), history of abortions 2.09 (95% CI 1.19 to 3.67), khat chewing 6.67 (95% CI 2.95 to 15.06), antipyretic and analgesic medications 2.87 (95% CI 1.47 to 5.56) and, being a female neonate 2.11 (95% CI 1.21 to 3.67) were significantly associated with a neural tube defect.

CONCLUSION

This study has identified some determinants of neural tube defects. Hence, the behavioural, medical and obstetrical conditions of mothers need serious evaluation in the prepregnancy period. So, improving preconception counselling and prenatal care practices would have a significant role in reducing the risk of neural tube defects.

Global prevalence of congenital anencephaly: a comprehensive systematic review and meta-analysis

Background

Anencephaly is a fatal congenital anomaly characterized by the absence of brain hemispheres and cranial arch. Timely preventive measures can be taken by knowing the exact prevalence of this common neural tube defect; thus, carried out through systematic review and meta-analysis, the present study was conducted to determine the worldwide prevalence, incidence and mortality of anencephaly.

Methods

Cochran’s seven-step instructions were used as the guideline. Having determined the research question and inclusion and exclusion criteria, we studied MagIran, SID, Science Direct, WoS, Web of Science, Medline (PubMed), Scopus, and Google Scholar databases. Moreover, the search strategy in each database included using all possible keyword combinations with the help of “AND” and “OR” operators with no time limit to 2021. The I² test was used to calculate study heterogeneity, and Begg and Mazumdar rank correlation tests were employed to assess the publication bias. Data were analyzed by Comprehensive Meta-Analysis software (Version 2).

Results

In this study, the statements of Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA) were used. In the first stage, 1141 articles were found, of which 330 duplicate studies were omitted. 371 articles were deleted based on the inclusion and exclusion criteria by reviewing the title and abstract of the study. 58 articles were removed by reviewing the full text of the article because it was not relevant to the research. 360 studies with a sample size of 207,639,132 people were considered for the meta-analysis. Overall estimate of the prevalence, incidence and attenuation of anencephaly worldwide were 5.1 per ten thousand births (95% confidence interval 4.7–5.5 per ten thousand births), 8.3 per ten thousand births (95% confidence interval 5.5–9.9 per ten thousand births), 5.5 per ten thousand births (95% confidence interval 1.8–15 per ten thousand births) respectively the highest of which according to the subgroup analysis, belonged to the Australian continent with 8.6 per ten thousand births (95% confidence interval 7.7–9.5 per ten thousand births).

Conclusion

The overall prevalence of anencephaly in the world is significant, indicating the urgent need for preventive and treating measures.

Anencephaly is a fatal congenital anomaly characterized by the absence of brain hemispheres and cranial arch. Cochran’s seven-step instructions were used as the guideline. Having determined the research question and inclusion and exclusion criteria, we studied MagIran, SID, Science Direct, WoS, Web of Science, Medline (PubMed), Scopus, and Google Scholar databases. Moreover, the search strategy in each database included using all possible keyword combinations with the help of “AND” and “OR” operators with no time limit to 2021. Out of 1141 initial articles found, and after excluding repetitive ones in various databases and those irrelevant to inclusion criteria, 360 studies with a sample size of 207,639,132 people were considered for the meta-analysis. Overall estimate of the prevalence, incidence and attenuation of anencephaly worldwide were 5.1 per ten thousand births (95% confidence interval 4.7–5.5 per ten thousand births), 8.3 per ten thousand births (95% confidence interval 5.5–9.9 per ten thousand births), 5.5 per ten thousand births (95% confidence interval 1.8–15 per ten thousand births) respectively the highest of which according to the subgroup analysis, belonged to the Australian continent with 8.6 per ten thousand births (95% confidence interval 7.7–9.5 per ten thousand births). The overall prevalence of anencephaly in the world is significant, indicating the urgent need for preventive and treating measures.

The association between maternal parity and birth defects

BACKGROUND

Previous studies observed that first birth is associated with an increased risk of some categories of birth defects. However, multiple statistical tests were conducted and it was unclear which of these associations would be replicated in a larger study. We used a large database to assess the association between maternal parity and 65 birth defects including birth defects that have not been previously studied.

METHODS

Using data from the Texas Birth Defects Registry for years 1999-2009, the risk of a birth defect occurring in a first, third, or fourth or higher birth was compared to the risk of a birth defect occurring in a second birth.

RESULTS

Women having their first birth had significantly increased odds of having an infant with 24 of 65 categories of birth defects when compared to women having their second birth. We also observed associations between first birth and an increased risk of five birth defects not previously reported (small penis, preaxial polydactyly, anomalies of the thoracic vertebrae, anomalies of the lumbar vertebrae, and sacroccygeal anomalies). Women having their third or fourth or higher birth had significantly increased odds of giving birth to infants with five of 65 birth defects when compared to second births.

CONCLUSIONS

Our observations regarding the categories of birth defects that were associated with first births were highly consistent with observations from two previous studies. Research into biological, behavioral, and environmental factors that may increase the risk of specific birth defects among first births is needed to further explore these associations.

'Miscarriage or abortion?' Understanding the medical language of pregnancy loss in Britain; a historical perspective

Clinical language applied to early pregnancy loss changed in late twentieth century Britain when doctors consciously began using the term 'miscarriage' instead of 'abortion' to refer to this subject. Medical professionals at the time and since have claimed this change as an intuitive empathic response to women's experiences. However, a reading of medical journals and textbooks from the era reveals how the change in clinical language reflected legal, technological, professional and social developments. The shift in language is better understood in the context of these historical developments, rather than as the consequence of more empathic medical care for women who experience miscarriage.

Maternal miscarriage history and risk of anencephaly

Women with a history of reproductive loss may be at an increased risk of having an unfavourable outcome in subsequent pregnancies. Using data from a matched case-control study based on the record of the Epidemiological Surveillance System of Neural Tube Defects, we evaluated the association between history of maternal reproductive loss and the risk of anencephaly in three Mexican states. Mothers of 157 cases of anencephaly and 151 controls born during the period March 2000 to February 2001, were interviewed about their reproductive history and other additional factors, including socio-economic characteristics, prenatal care, use of tobacco and alcohol, presence of chronic diseases, acute illnesses and fever during the periconceptional period, and consumption of multivitamins and medicines during this period; mothers who reported no prior pregnancies were excluded from the analysis; 58 matched case-control pairs were used for the analysis. After adjusting for potential confounders, women with a history of miscarriage in previous pregnancies had 4.58 times more risk of having a child with anencephaly, than those who did not have this history; OR = 4.58, [95% CI 1.22, 17.23]. Our results suggest that a history of previous miscarriages is a risk indicator for anencephaly in future gestations. This does not necessarily mean that the miscarriage itself is the cause, but that common mechanisms could be involved in the aetiology of both events. Thus, women who have had histories of reproductive losses, especially miscarriages, should be a priority group for the primary and secondary prevention of neural tube defects.

Autoantibodies against folate receptors in women with a pregnancy complicated by a neural-tube defect

BACKGROUND

In the absence of clinical folate deficiency, periconceptional supplementation with folic acid reduces a woman's risk of having an infant with a neural-tube defect. Since antiserum to folate receptors induces embryo resorption and malformations in rats, we hypothesized that autoantibodies against folate receptors in women may be associated with pregnancy complicated by a neural-tube defect.

METHODS

Serum from 12 women who were or had been pregnant with a fetus with a neural-tube defect and from 24 control women (20 with current or prior normal pregnancies and 4 who were nulligravid) was analyzed for autoantibodies by incubation with human placental folate receptors radiolabeled with [3H]folic acid. The properties of these autoantibodies were characterized by incubating serum and the autoantibodies isolated from serum with placental membranes, ED27 cells, and KB cells, which express the folate receptors.

RESULTS

Serum from 9 of 12 women with a current or previous affected pregnancy (index subjects) and 2 of 20 control subjects contained autoantibodies against folate receptors (P<0.001). The autoantibodies blocked the binding of [3H]folic acid to folate receptors on placental membranes and on ED27 and KB cells incubated at 4 degrees C and blocked the uptake of [3H]folic acid by KB cells when incubated at 37 degrees C.

CONCLUSIONS

Serum from women with a pregnancy complicated by a neural-tube defect contains autoantibodies that bind to folate receptors and can block the cellular uptake of folate. Further study is warranted to assess whether the observed association between maternal autoantibodies against folate receptors and neural-tube defects reflects a causal relation.

Neural tube defects in Victoria, Australia: potential contributing factors and public health implications

OBJECTIVES

To measure population prevalence and determine potential predictors of neural tube defects.

METHOD

Analysis of all births reported to a mandated collection of perinatal data, and terminations prior to 20 weeks' gestation that have been reported to a data collection of birth defects in Victoria from 1983 to 1997. Prevalence at birth and risk ratios of infant and maternal characteristics associated with neural tube defects were calculated.

RESULTS

Prevalence of spina bifida has remained steady for 15 years and was 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After exclusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are identified in 1 in 1600 fetuses, the risk being significantly higher for epileptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% CI 2.25-6.07), multiple births (AOR = 4.56, 95% CI 3.46-6.02), teenage mothers (AOR = 1.47, 95% CI 1.09-2.00) compared with those aged 25-29, and women with three or more previous pregnancies (AOR = 1.40, 95% CI 1.10-1.78). The risk was lower for women of East Asian (AOR = 0.70, 95% CI 0.49-1.00) and Middle Eastern origin (AOR = 0.60, 95% CI 0.35-1.02) and these differences were approaching statistical significance.

CONCLUSION

Total prevalence of neural tube defects did not decline up to 1997.

IMPLICATIONS

It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. However, consideration could be given to identifying larger 'at risk' groups such as those with homocysteine metabolism defects.

Maternal factors associated with severity of birth defects

OBJECTIVE

Due to inbreeding and nutritional factors, the Bedouin Arabs represent a high risk population for birth defects. The severity of birth defects is probably related to the time and extent of interference with embryogenesis. The present study was aimed at identifying factors associated with severity of birth defects, in pregnancies of Bedouin women examined at a third level ultrasound clinic.

METHODS

The study population consisted of 295 Bedouin women who attended an ultrasound clinic at the Soroka Medical Center between 1990 and 1996. The case group included 188 women carrying fetuses with severe birth defects, defined as incompatible with life or which significantly interfere with normal living. For those defects the option of pregnancy termination was discussed. The comparison group consisted of 107 women whose fetuses were diagnosed with mild defects.

RESULTS

Women carrying fetuses with severe birth defects had more pregnancies and more deliveries than women carrying fetuses with mild defects (P = 0.005, P = 0.04, respectively). The severity of defects was found to be unrelated to maternal age, consanguinity, residence, birth order, previously uncompleted pregnancies and birth defects in the family.

CONCLUSIONS

Higher birth order was associated with severity of birth defects detected at the second trimester.

Spontaneous abortion--high risk factor for neural tube defects in subsequent pregnancy

An increased spontaneous abortion rate has been observed in pregnancies preceding that of fetuses or newborn infants with neural tube defects (NTDs). There are 2 suggested explanations for this observation. One is that a trophoblastic cell rest, remaining from a previous aborted pregnancy, interferes with normal embryogenesis. The second is that the previous lost fetus was affected with NTD. We studied the obstetric history of mothers of newborn infants with NTDs compared to those with other birth defects, in low and high risk groups for NTD (Jew and Bedouins). A significantly higher spontaneous abortion rate (48%) in the preceding pregnancy was found in the NTD group compared to the group with other birth defects (20%). This was especially remarkable for spina bifida cases in the Jewish study population. A significantly higher rate of preceding spontaneous abortion was also found in congenital heart defects (CHD) when compared to other congenital malformations. A hypothesis based on the multifactorial threshold model is put forward to explain these findings. Based on the realization that spontaneous abortion constitutes a high risk factor for NTD and possibly also CHD, we recommend a delay of subsequent pregnancy and periconceptional treatment with folic acid following spontaneous abortion.

A case-control study to investigate the role of recent spontaneous abortion in the aetiology of neural tube defects

Clarke et al. suggested that women who have had a spontaneous abortion are at an increased risk in their next pregnancy of producing an offspring with a neural tube defect (NTD). A matched case-control study was carried out to test the related hypothesis that a spontaneous abortion occurring in the 6-month period prior to the conception of a pregnancy (recent spontaneous abortion) is a risk factor for the development of an NTD in that pregnancy. The cases were 177 singleton pregnancies to non-primigravida Leicestershire women, which were affected by non-syndromal NTDs between 1976 and 1989. Two control pregnancies were matched with each case on intended place of delivery and date of maternal last normal menstrual period (LNMP). After adjusting for potential confounders, recent spontaneous abortion was found to be associated with a decreased relative risk of neural tube defect, odds ratio 0.46, 95% confidence interval 0.20, 1.07. The result provided little evidence in favour of the hypothesis, suggesting instead that prior spontaneous abortion has a protective effect in relation to subsequent NTD development rather than being a major risk factor in the aetiology of NTDs.

Clinical, genetic, and epidemiological factors in neural tube defects

We examined clinical, genetic, and epidemiologic factors among 512 probands with nonsyndromal neural tube defects (NTDs). Data were analyzed after grouping the probands in four different ways with respect to pathological features and putative pathogenic mechanisms. Apparently unrelated congenital anomalies occurred more frequently among probands with craniorachischisis (62%), encephalocele (30%), or multiple NTDs (25%) than among probands with anencephaly (14.7%) or spina bifida (10.1%) (P much less than .0001). Unrelated congenital anomalies occurred less often among probands with low spina bifida (6.7%) than among probands with high spina bifida (19.5%). NTDs were seen in 7.8% of the siblings of probands with high spina bifida but in only 0.7% of the siblings of probands with low spina bifida, in 2.2% of the siblings of anencephalic probands, and in none of the siblings of probands with craniorachischisis, encephalocele, or multiple NTDS (P less than .001). In all 16 families in which two siblings had NTDs, both had either defects of the type associated with abnormal primary neurulation or defects of the type associated with abnormal canalization. High spina bifida and multiple NTDs were found more frequently than expected among the Sikh probands (P less than .02). The frequency of non-NTD congenital anomalies was higher among siblings of Sikh probands (8.8%) than among siblings of other probands (2.4%) (P less than .05). This excess was due to the occurrence of hydrocephalus without spina bifida in four of 68 siblings of Sikh probands.

Studies in neural tube defects. I. Epidemiologic and etiologic aspects

In the NIH Collaborative Perinatal Project, a prospective study of over 53,000 pregnant women and their offspring, 71 single-born children (13.33/10,000) were found to have a non-syndromal neural tube defect (NTD). A family history was present in only one case. The group of individuals with NTD was compared to a group of 400 randomly selected non-malformed control infants. Of over 50 maternal factors studied the following showed significant association with NTD in the offspring: diabetes mellitus; organic heart disease; lung disease; and diuretic, antihistamine, and sulfonamide use. The interval between the termination of the immediately previous pregnancy and the start of the proband pregnancy was significantly shorter in mothers of NTD children than in mothers of control infants. The risk for NTD was also significantly increased if the immediately previous pregnancy was a spontaneous abortion. There was no increased risk for NTDs among sibs of children with major malformations such as tracheo-esophageal "dysraphism," cleft lip/palate, or renal agenesis. NTDs are apparently etiologically heterogeneous.

Risks to sibs of probands with neural tube defects: data for clinic populations in British Columbia

The purpose of this study is to determine whether couples receiving genetic counselling because of a child with a neural tube defect (NTD) are a selected group and therefore not representative of the general population with respect to sib risks for NTDs. British Columbia (B.C.) provides an excellent opportunity to look at this for several reasons. Firstly, genetic counselling services are centralized. Secondly, there is virtually complete ascertainment of all infants with NTDs in the province. Thirdly, sib risks for NTDs in the general population have been derived previously [McBride, 1979] and, therefore, are available for comparison with the risks for sibships in the clinic populations. In the present study, data were available on 398 sibships in which the index case had anencephaly and/or spina bifida. In all instances, sib risks for the clinic populations did not differ significantly from those for the general population. In addition, congenital malformations other than NTDs did not occur among sibs of index cases more often than expected, based on provincial incidence data.

Fetal mortality in sibships of cases with neural tube defects

Rates of fetal mortality in sibships of probands with neural tube defects (NTDs) may reflect liability to NTDs. Expectations from the multifactorial model predict that fetal loss should be higher in sibships of male probands; in multiplex sibships; and sibships where the proband had no additional malformations. This was analysed for 715 pregnancies from 398 sibships. In general, the results did not support the expectations of the multifactorial model.

Fetal mortality in sibships of cases with neural tube defects

It has been suggested that rates of fetal mortality in sibships of probands with a malformation inherited as a multifactorial threshold trait may reflect their liability to the malformation. If so, spontaneous abortion rates should be more frequent in sibships thought to have greater liability. For anencephaly and spina bifida (ASB), then, spontaneous abortion should be higher in the sibships of male probands and in families with more than one affected case (multiplex families). This hypothesis was tested using data on cases from The Montréal Children's Hospital and from the literature. Approximately 5000 pregnancies were analyzed. Rates of abortion did not vary with the sex or diagnosis of the proband. The spontaneous abortion rate was slightly higher in multiplex than in simplex families, but the difference was not statistically significant and most likely reflects the differing reproductive patterns in the two types of families. Thus, if male probands and multiplex sibships do have, on average, more liability for ASB, this liability cannot be detected in spontaneous abortion rates in the sibships available for this analysis.

Recurrence risk after neural tube defects in a genetic counselling clinic

The recurrence of isolated neural tube defects in a population of women from a genetic counselling clinic was found to be 3.4%. After one baby with a neural tube defect the recurrence was 2.3%. Of the 15 pregnancies of women who had two previous babies with neural tube defects, there were three further recurrences. These findings show that the Hungarian recurrence risk of isolated neural tube defects has not changed with a declining birth prevalence, and that the rate in genetic counselling clinic patients is the same as in a previous population based epidemiological study.

Neural tube defects in Eastern Ontario and Western Quebec: demography and family data

This paper reports the results of a study of families in the Eastern Ontario/Western Quebec region who had a child born with a neural tube defect during the years 1969-1981. As in several other geographic areas, the prevalence of neural tube defects at birth has fallen from previous levels. However, there was no evidence of further decline during the period of study. Socioeconomic and ethnic influences were noted, but there was no evidence of seasonal variation or any correlation with maternal age or parity. There was support for a causative role of maternal fever in some cases. The rates of miscarriage varied between pregnancies before and those after the proband, and there was an excess of males born prior to the proband. Family studies showed a 2.4% risk for sibs born after the proband and an excess of affected relatives on the maternal side. Knowledge of rates of occurrence in relatives is useful for counseling and the interpretation of the results of alpha-fetoprotein screening.

Oral contraception and congenital abnormalities

Of 10 479 single births in South Glamorgan between January 1974 and June 1976, 27.3 per cent of infants were born to women who had used oral contraception in the three months prior to their last menstrual period (users) and 72.3 per cent were born to women who had not used oral contraception during the same period (non users). There were significantly more infants with neural tube defects among users compared with non users. Abnormalities of the digestive, genito-urinary and cardiovascular system, bones, muscle, skin and connective tissues, endocrine glands, blood chromosomes and oral clefts, were of similar incidence in the two groups.