A Latin American study on congenital malformations has shown that there was an excess of cases of SBA in populations living at high altitude (28
A hypoxia mechanism derived from high altitude could be involved in the etiopathogenesis of some ADAM cases and the other described defects. Another explanation could be ethnicity, since Bolivian population studied here are mainly from Amerindian extraction (29
According to the results of this study there was a familial occurrence of the syndrome. The risk of ADAM sequence was 42.8 times higher among the first-degree relatives, and 50.8 times higher among the second degree relatives than the risk in the general population (0.0000894) (30
). Cases with ADAM sequence were more firstborn than controls (OR: 2.16; CI: 1.25–3.72); there were more acute illness (OR: 2.00; CI: 1.08–3.72), medication drug use (OR: 2.38; CI: 1.32–4.26), in three of these cases misoprostol was the drug responsible, and vaginal bleeding (OR: 2.00; CI: 1.00–4.00) during the first trimester of pregnancy among cases than controls. Birth weight lower than 2,500 g was in excess among cases (OR: 5.55; CI: 2.92–10.54), which could be explained by intrauterine growth retardation (OR: 4.25; CI: 1.43–12.63), as well as by prematurity (OR: 4.86; CI: 2.15–10.96).
Non-cephalic fetal presentation was also more frequent among cases than controls (OR: 2.33; CI: 1.07–5.09).
A case-control study carried out on metropolitan areas of Boston, Philadelphia and Toronto concluded that ARS (amnion rupture sequence) and BWC (presence of body wall defects with evisceration of thoracic and/or abdominal organs, limb deficiency, and myelocystocele) are two different disease entities, based on different epidemiological and etiological factors. This study collected epidemiological data from 1976 to 1998. There were 73 cases with ARS and 11 with BWC.
ARS cases were further subdivided according to affected structures: there were 53 with only limbs affected (ARS-L) and 20 with non limb defects with or without limb defects (ARS-NL).
Risk estimates tended to be similar for ARS-L and ARS-NL cases but different for BWC cases, suggesting different etiologies. Parity was the one exception to this pattern, where ARS-NL and BWC case mothers had similar histories. Parity was not a statistically significant risk factor, but the observed approximate twofold increases in risk of ARS-NL and BWC for a first birth suggest it may be important. Why first birth in and of itself would be related to these defects is not clear, but the vascularity of a multigravid uterus is likely to be different than that of a primigravid uterus.
Data from the study of Boston suggest that young maternal age, low maternal education, unplanned pregnancy, and non-white/non-Hispanic race/ethnicity might increase the risk of BWC in offspring. It is not clear if the reduced risks for white non-Hispanic offspring were due to socioeconomic status (beyond differences in maternal age and education) or whether there might be a genetic basis.
The same study estimated the ARS does not recognize these conditions as risk factors.
A Hungarian study examined isolated amniogenic limb defects (equivalent to ARS-L) and reported no association for maternal age (31
), similar to what observed in the first study (32
In contrast to those and findings of the American study, the Hungarian study found multiparous women had a greater risk association for maternal age (33
). The Hungarian study also reported positive associations for low socioeconomic status, unplanned pregnancy, and smoking during pregnancy in relation to ARS-L, contrary to findings of the American study for that defect. In reality, the Hungarian study has some limitations. ARS and BWC diagnoses were determined by medical record reports and study investigators did not separately confirm them by examination of the baby or placenta. Since difficulties in accurate diagnosis and classification of ARS and BWC diagnoses are well recognized, there is a real possibility of misclassification.
Cigarette smoking during early pregnancy is vasoconstrictive and has been related to gastroschisis, which is thought to arise from vascular disruption (34
). However, maternal smoking was not found to be associated with ARS or BWC in the American study.
Acetaminophen is one of the most commonly used medications during pregnancy (37
). The American study observed that use of acetaminophen in early pregnancy was associated with increased risks of ARS cases but not BWC cases. Acetaminophen is not known to be vasoactive, but it has been associated with a slight increase in gastroschisis risk in two studies (38
Increased risks for acetaminophen use should be interpreted with caution because they may be confounded by indication for use (40
). In particular, there may be confounding by fever as acetaminophen is an antipyretic and hyperthermia has been implicated as a vascular disruptor (41
There is a Californian study according to which young paternal age, i.e., less than 29 years, was associated with an increased risk of amniotic bands (OR: 0.87 [0.78, 0.97]).
This study examined the association between paternal age and a wide range of structural birth defects. Younger paternal age, was associated with a higher risk of amniotic bands, pyloric stenosis, and anomalies of the great veins, with the risk decreasing between 7 and 13% for every 5-year increase in father’s age (42
There is, however, no clear biological mechanism for the association between younger paternal age and birth defects. The increase in risk observed among younger fathers in our study could be attributable to an interaction of genetic factors with behavioral factors such as the use of alcohol and recreational drugs (43
Data were drawn from The California Birth Defects Monitoring Program, a population-based active surveillance system for collecting information on infants and fetuses with defects born between 1989 and 2002. In the aforementioned research, however, there is a lack of consistency across studies with respect to the source of data on birth defects, the range of birth defects examined, and the methods for analyzing maternal age.
In a study conducted by the National Center on Birth Defects and Developmental Disabilities (Centers for Disease Control and Prevention, Atlanta, GA) has been observed that Maternal cigarette smoking and aspirin use each increased the risk of AB-L (Limb reduction deficiencies that are accompanied by amniotic bands) (44
Cases with amniotic bands were also associated with glycaemic intake, but unlike anorectal defects and neural tube defects (NTDs), which were seen to be associated particularly maternal obesity, the effect appeared to be confined to carbohydrate quality (dietary glycemic index). One study with only 12 amniotic band cases reported no association with obesity (45
Several workers have been able to produce experimentally typical amputations, cranial malformations, and syndactylies, even in the absence of band formation, with amniocentesis (46
) amnioreduction or septostomy in twins. They noted vascular changes, and hemorrhage or hematoma as the primary event. In some cases, secondary adhesions to the amnion could exist (48
It also described a case of monochorionic biamniotic twin pregnancy submitted to selective fetoscopic laser photo-coagulation for twin-to-twin transfusion syndrome at 16 weeks of gestation. The procedure was complicated by the death of one of the fetuses at 24 weeks of gestation. Moreover, the surviving twin was diagnosed postnatally with pseudoamniotic band syndrome, presenting with affected limbs. The incidence and risk factors for Pseudoamniotic band syndrome (PABS) after fetoscopy-guided laser have not been documented (49