For instance, routine weighing is so much a part of the ante natal regimen that it has largely escaped any kind of critical assessment. In a survey of the attitudes of general practitioners to routine weighing, it was revealed that most saw it primarily as a tool for detecting pre-eclampsia (BMJ, 1992; 304: 487-9). However, as the authors point out, pre-eclampsia can only be reliably diagnosed by measuring blood pressure and analysing urine for protein. While there is an association with greater than average weight gain in the second half of pregnancy and the disease, the weight gains of women with and without pre-eclampsia overlap to such an extent that weight gain in an individual woman is of little predictive value (Br J Ob Gyn, 1991; 98: 189-94; BMJ, 1957; i: 243-7) .
Also, weight gain in itself is not a reliable predictor of a healthy or unhealthy baby. Gaining 36 pounds on crisps and sodas will not ensure the health of a baby, as one reported story poignantly illustrates. After her daughter died of eclampsia, a mother contacted a pre-eclampsia support group. Eventually the advisor asked: "Did she eat well?" The mother answered: "Yes, she ate like a horse. . . chips, pies, sausages and pear drops. Loads and loads of pear drops." (PETS Newsletter, No 20).
Pregnant women also need to drink freely. Free intake of fluids helps to keep the kidneys working well, flushing waste products out of the system. The normal swellings of ankles, face, feet and hands which 80 per cent of women experience are not a cause for concern in a healthy, well nourished individual, and should not be confused with the pathological swelling that comes with pre-eclampsia.
Nevertheless, doctors sometimes prescribe diuretics to treat oedema. But diuretics deplete the body of essential salt and fluids, creating even more problems. Results from 10 randomised, controlled trials involving 7000 pregnant women showed that while diuretic treatment reduced hypertension and oedema, it did not prevent pre-eclampsia or reduce prenatal mortality (BMJ, 1985; 290: 17-23).
And what of restrictions on salt? Pregnant women need salt as much as any of us perhaps more. The greater volume of blood in a pregnant woman's body means that she will be sweating more and secreting greater quantities of salt through her sweat.
Salt helps to regulate the fluid balance in the body and is essential for the proper functioning of nerves and muscles. Historically, restriction of salt has not been shown to reduce the incidence of pre-eclampsia (Eur J Ob Gyn Reprod Biol, 1991; 40: 83-90).
This fact was underscored in 1958 when a study at St Thomas's Hospital in London revealed the dangerous consequences of restricting salt. In the study, 1000 women were told to decrease their salt intake, while another group of 1,019 were instructed to increase the salt in their diet. The women on low salt diets had much higher rates of pre-eclampsia and eclampsia, as well as higher rates of miscarriage, perinatal deaths, caesareans and other complications (Lancet, 1958; i: 178). With hindsight, this was a highly unethical trial, which resulted in unnecessary damage, trauma and deaths for many pregnant women and their babies.
Besides diuretics, the kinds of drugs used to treat pre-eclampsia include low doses of aspirin, tranquillisers, mood altering drugs, muscle relaxants (known as tocolytics) to forestall the onset of labour, drugs to reduce blood pressure (anti hypertensive drugs) and drugs to thin the blood (anti coagulants). There is very little evidence to show that any of them do much good (M Enkin, Effective Care, as above). What is more, doctors may be over reacting, since in pregnancies with mild to moderate pre existing essential hypertension, 90 per cent are associated with good maternal and neonatal outcomes (Compr Ther, 1995; 21: 227-34; Ob Gyn 1986; 67: 197-205).