Cloud Engineer | Tech Lead
I wrote this paper around 2014 during my masters. It was quite interesting to do a deep-dive in a completely different domain.
Among the severest and rarest of fetal deformations is acephaly, the absence or detachment of the fetal head. In most cases, acephaly is caused by twin reversed arterial perfusion[1]. This etiopathological mechanism entails a parasitic twin that reduces nutrient streams needed for development of the dominant fetus’ head. However, in ten cases, no parasitic twin was found [2-8]. This paper examines available case reports and possible explanations for this anomaly. Constriction by amniotic band sequence (ABS) is considered most likely and will be central to the observations of this paper. Firstly, an overview of ten known cases will be presented. Different explanations for the anomaly will be compared secondly, followed by concluding remarks.
For the purpose of this paper, only observations relevant to the hypothesis of ABS have been selected. Clubfoot is weakly correlated with ABS, but may have other causes. Complete absence of the fetal head may indicate congenital malformations of the central nervous system rather than decapitation through amniotic band constriction. It is also worth noting that in most cases, the fetal heart was still operational up until twenty minutes after delivery. In recent cases, the pregnancy was terminated with the fetus still alive [3-5, 7, 8] after identification of malformation with sonar equipment. The acephaly case as described by Gonzalez resulted in spontaneous vaginal delivery [6].
The medical consensus is that constriction by amniotic bands is the most likely cause of acephaly [2-7]. However, Mazzitelli et al. point out that in only one case (the team failed to note the observations by Glass and Gonzalez) amniotic bands were actually identified [8]. Amniotic bands are invisible until the placenta is submerged in water, allowing the bands to visibly float. Mazzitelli et al. argues that these barely visible bands, if present at all, are unlikely to cause severe amputation. In general, proof for ABS as definite cause of acephaly is concluded to be feeble. Other etiopathological mechanisms are suggested, such as the attachment of the fetus’ head to the placenta, causing movement restriction and decapitation. Another explanation could be disrupted vascular integrity, which leads to a similar effect as the TRAP sequence described earlier.
As mentioned, Mazzitelli et al. did not include an important finding by Glass, which involves visible amniotic bands and the presence of the detached fetal head. This finding adds to the evidence base of ABS as main etiopathological mechanism. My own observation is that all researchers are venturing to identify a single causal pathway to acephaly, while it seems perfectly possible that different causes can lead to the same deformation. At the present time, no conclusive evidence exists to the cause(s) of fetal decapitation.