In Drug and Therapeutics Bulletin, researchers say they looked at all evidence and found supplements did not boost the health of mothers and babies.
But pregnant women should make sure they take folic acid and vitamin D, as well as eating a well-balanced diet, as per NHS guidelines, they add.
Supplements-makers said some women were not getting enough nutrients.
The researchers said folic acid had the strongest evidence to support its use - taking 400 micrograms a day can protect against abnormalities called neural tube defects in the developing baby.
Vitamin D - 10 micrograms a day - is recommended for healthy bones in the mother and baby.
Some women can get these two pills for free on the Healthy Start scheme.
A supplement that can be dangerous in pregnancy is vitamin A. Too much can harm the baby.
The researchers said pregnant women might feel coerced into buying expensive multivitamins in order to give their baby the best start in life.
But they would do well to resist the marketing claims, which did not seem to translate into better outcomes for mother or baby, they said.
"The only supplements recommended for all women during pregnancy are folic acid and vitamin D, which are available at relatively low cost," they said.
Janet Fyle, from the Royal College of Midwives, said: "We would encourage women who are pregnant or are thinking of becoming pregnant to have a healthy, varied diet including fresh fruit and vegetables, alongside taking folic acid supplements.
"We would also stress that there is no need for pregnant women to 'eat for two'.
"This is a myth, and all that is required is a normal balanced amount of food."
The Health Food Manufacturers' Association, which represents the food supplements industry, insists that a substantial proportion of women of child-bearing age are not getting enough nutrients from diet alone.
The industry-funded Health Supplements Information Service said food supplements could help plug dietary gaps.

Councillor Richard Kemp named and shamed companies which sell fast food as he called for a sugar tax.
He wants the city solicitor to work with the director of public health to draw up a Parliamentary bill regulating sugar in food.
Councillor Kemp said a Soil Association report highlighted meals available in "Pizza Hut, Frankie and Benny's and Nando's" for excess sugar.
The fast food companies have been contacted by the BBC but have not commented.
Councillor Kemp said the city led the way on the smoking ban and could be pioneering on sugar.
His proposal requests the city solicitor works with the director of public health to draw up a Parliamentary Bill "which would give the council powers to regulate the amount of sugar in foods sold in fast food outlets, restaurants and takeaways".
It also asks the director of public health to work with the Clinical Commissioning Group to promote a health awareness campaign within the city to highlight the real dangers to long-term health of excessive salt and sugar in diets.
Mr Kemp said: "If a child has two fizzy drinks and a fluffy ice-cream pudding they will have consumed seven times the daily recommended sugar".
He said the smoking ban in public places began in Liverpool and led to pressure on the government, adding if "we have a city of people that waddle, we will have a city that dies early".
Professor Simon Capewell, from Liverpool University, who founded Action on Sugar, said the campaign needed to target the "affordability, availability and acceptability" of sugar.
McDonald's, although not identified by Councillor Kemp, said it has carried out "extensive work" to evolve its recipes and reduce sugar and salt for "over 30 years" and provides customers with clear nutrition information.
Pregnancy multivitamins are a waste of money because most mothers-to-be do not need them, according to researchers.
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A tax on fast food with hidden sugar is being considered in Liverpool.