Few topics generate such a passionate division in opinion as abortion and ultimately there is no easy answer when choosing between an unborn child’s right to life and a woman’s right to freedom over her own body. However, after reading about the uproar caused by the tragic death of Savita Halappanavar, I knew I wanted to add my own voice to this debate. Which left me pondering the following question: what can a science blog bring to the table when tackling a heated moral debate like this?
The answer, I believe, is something few mainstream sources address: the development of the brain and consciousness (as we understand it) in the growing fetus.
Of course if you are of the opinion that ‘life begins at the moment of conception’ the emergence of consciousness is probably a moot point. However, according to recent statistics more than 60% of UK adults and 18-35 year-olds in the republic of Ireland are pro-choice. This means that, under certain circumstances, they accept abortion as a viable option, raising a particularly difficult question. Assuming abortion, in theory, is acceptable, is there a point during the pregnancy when it becomes unacceptable and how do we decide where to draw this line?
Current UK legislation states that an abortion must be carried out during the first 24 weeks of pregnancy. However, guidelines also state that the procedure should ideally be performed before 12 weeks. Current legislation bases its ‘upper limit’ on the survival rate of premature babies, which is significantly reduced prior to 24 weeks (Percentage of babies successfully discharged from hospital after premature birth at 24 weeks: 33.6%, 23 weeks: 19.9%, 22 weeks:9.1%).
Almost 90% of UK abortions are performed within the first 12 weeks of pregnancy. During this time there is no scientific doubt that the developing fetus is incapable of any form of conscious awareness. The fetal brain does not begin to develop until 3-4 weeks into the pregnancy, at which point it is little more than a hollow tube filled with dividing neurons. Between weeks 4 and 8 this neural tissue grows forming the major divisions of the adult brain (forebrain, midbrain, hindbrain and spinal cord). By 8 weeks recognisable facial features have developed and the cerebral cortex separates into two distinct hemispheres. By the end of the first trimester (12 weeks) nerve cells are beginning to form rudimentary connections between different areas of the brain. However, these connections are sparse and incapable of performing the same functions as an adult brain. So by 12 weeks, although the fetus is certainly starting to look like a little human, the neural circuits responsible for conscious awareness are yet to develop.
The first trimester is also the time when around three quarters of spontaneous miscarriages occur. Miscarriages are possible throughout the pregnancy and are much more common than most people realise. One in eight women who are aware of their pregnancy experience a miscarriage, with many more occurring before the woman is even aware she has fallen pregnant.
As the complexity of the fetal brain grows, forming structures similar to those we recognise in the adult, so the does the fetus’ ability to experience and respond to its environment. Indeed, studies have shown that from 16 weeks the fetus can respond to low frequency sound and by 19 weeks will withdraw a limb or flinch in response to pain. An observer would certainly think these responses look very much like the start of conscious awareness. However, during these early days the neural pathways responsible for converting senses to conscious experiences have yet to develop. This means what we are seeing are just reflexes, probably controlled entirely by the developing brainstem and spinal cord.
In fact, we know that the brain structures necessary for conscious experience of pain do not develop until 29-30 weeks, while the conscious processing of sounds is only made possible after the 26th week. Even when the fetal brain possesses all its adult structures, scientists are cautious to assume it posesses what we refer to as ‘consciousness’. This is mainly because the low oxygen levels and a constant barrage of sleep-inducing chemicals from the placenta ensure that, until birth, the foetus remains heavily sedated.
Ultimately, although science cannot and should not try and answer the moral questions behind abortion, it can give us some amazing insights into how the brain develops. It seems that, in the womb, a fetus is unlikely to ever experience traditional consciousness. However, we do know that from the time neural pathways are in place (the last weeks before birth) the fetus can form rudimentary memories. Meaning that after birth it can show a preference for its mother’s voice and other sounds and smells experienced in the womb – yes, newborn babies show a liking for the smell of amniotic fluid.
Therefore, although the ‘upper limit’ on abortion remains relatively arbitrary. Its current position at 24 weeks appears to fit well with both premature birth survival rates and, in terms of neural development, a time before any major connections are in place. Making it, in my eyes, as pretty good point at which to draw this line.
Post by: Sarah Fox