While attending the obstetric unit as a young medical student at my London teaching hospital 60 years ago, I regularly observed the tranquillity and happy, eager anticipation of the many young expectant mothers.
My professor had impressed upon me that pregnancy was not a disease – it was a normal condition. Very occasionally, however, an expectant patient was admitted to the ward with a strange disease called ‘toxaemia of pregnancy’. What was it? Nobody knew its origin but sometimes it could cause an illness in the mother and foetus. Such a mystery sat uncomfortably within the enduring normal culture of pregnancy for many years.
Then some brilliant findings around this state of affairs emerged. Starting in the 1970s, evolutionary biologist Robert Trivers (lauded by both Steven Pinker and Richard Dawkins) became the first scientist to realise that the genetic make-up of both the mother and foetus were not quite the same, and were, in fact, bound in a rather silent, rivalrous dance in the womb, and therefore could produce less-than-ideal reactions between them.
Both Trivers and another evolutionary biologist, David Haig, performed much research in the 1990s which showed that there existed a perfectly normal mechanism of competition for control between the mother and the foetus, carrying the somewhat alarming name ‘intragenomic conflict’.
These studies revealed that the foetus normally used several methods to steadily increase the food and oxygen supply from the mother for maintaining rapid growth and development. Nature is nothing if not clever! After all, life always tries to find a way, as they say.
Faced with a very real failure to survive, the foetus makes a desperate attempt to alert the mother by secreting a toxin
One method involved the foetus secreting a growth hormone which stimulated the cells of the placenta to invade the lining (endometrium) of the womb, causing widening and straightening of the hitherto spiral uterine wall arteries. Thus there was increased flow (about 30 times) of nutrients from the mother to the foetus.
Trivers also noted that, conversely, failure of placental penetration into the uterus caused slow growth of the foetus and often precipitated detachment of the placenta from the uterus, leading to miscarriage.
Because of an ever-increasing appetite, the foetus also secreted hormones that increased maternal blood glucose and blood pressure, temporarily satisfying the foetus. However, the mother responded by secreting a hormone that blocked the effects of the foetal hormone so that maternal control of foetal demands for food occurred. Again, these silent operations, completely normal, would sometimes allow either mother or foetus to gain too much ascendancy in this ‘dance’ for control.
Haig then made the remarkable discovery that a third person – the father – that is to say, the father’s genetic contribution – could be involved in this mother-foetus ‘tango’ for control.
The father’s interest was due to the presence of his controlling gene accompanying a similar gene from the mother adjacent to the foetal appetite-controlling gene. The fact that these genes could be switched on and off accounted for the ‘see-saw’ flow of nutrients between mother and foetus.
If the paternal gene sensed the mother had excessively reduced nutrient flow to the foetus, then this gene could override the maternal gene, thus increasing the flow. Strangely, the maternal and paternal genes were identical in chemical structure, but produced opposite effects – a process known as ‘genetic imprinting’.
The reader may now think that the above reactions represent the beginning of a ‘dysfunctional family’, but these events are absolutely normal. Just very rarely, something goes awry with these reactions, resulting in the foetus being unable to acquire sufficient nutrients for growth.
Faced now with a very real failure to survive, the foetus makes a desperate attempt to alert the mother by secreting a toxin that shrinks the arteries in the uterine wall and damages the maternal kidneys, leading to the multisymptomatic condition we know as ‘toxaemia of pregnancy’. Thankfully, due to the good work of Trivers and Haig, the mystery of the appearance of this complication in an otherwise perfectly normal pregnancy was finally solved.
At last we now know the cause of this condition, which can be diagnosed in a timely fashion and treated appropriately to very good effect.
Dr Charles Corney is a medical practitioner and researcher.