Housewife Kay Park, 41, wanted to see a paediatrician, but on three occasions, she ended up being ambushed first by a formula milk company's marketer in the hospital clinic.
The representative from Dumex was "persistent", she said.
"I saw her inside the paediatric clinic, just outside the doctor's office, and each time, she asked what formula milk brand I used, and if I wanted to try her brand," said the mother of two sons, aged two and four.
"This happened in a clinic, not a supermarket. I think such an approach is overdoing it. I wouldn't be that concerned if it was just brochures or posters at the clinic."
While mothers interviewed by The Straits Times had mixed views on the companies' marketing strategies, most said such costs should not be passed on to consumers. Those interviewed were shocked to learn that marketing expenses were a key factor in the hike in formula milk's retail prices.
A report released by the Competition Commission of Singapore yesterday found that between 2010 and 2014, the amount that all major manufacturers spent on marketing increased 42.4 per cent.
The competition watchdog said that heavy spending in marketing and research likely led to the rise in the mark-up of wholesale prices.
This, in turn, was the main factor in hikes in retail prices - which have, on average, more than doubled over the past nine years.
Public servant Chiam Mei Si, 33, spends about $140 a month on formula milk for her 1½-year-old son.
She said: "It's shocking that their marketing costs have gone up by so much. The companies might be banking on the fact that mothers don't have much of a choice and want to buy the brand that works best for their children."
Pre-school educator Ng Mingzhu, 32, who has an 11-month-old daughter, added: "The companies usually say that the price increase is due to only higher R&D costs.
"That may play a part, but I think it's got more to do with aggressive marketing. It's disappointing, but I guess they are (profit-driven) private companies."
Most mothers said their doctors did not recommend specific milk brands, but cited instances of marketers from milk companies introducing their products at hospitals.
Lawyer M. Y. Yip, 39, who has two sons aged two and four, said: "They ask you to do a survey, get your e-mail address, put you on their mailing list and e-mail you their promotions.
"To thank you for doing the survey, they give you sachets of maternity milk and infant formula milk."
She added: "I didn't find the marketers particularly aggressive, and it doesn't bother me since I was waiting for my turn to see the doctor."
However, Ms Park has had worse experiences.
She said her older son was fed Nestle's Nan formula milk at the hospital the day he was born, and she was not asked about her preferred brand.
This may have led to him being unwilling to be breastfed and reluctant to switch to another brand that she preferred, she said.
Meanwhile, the Government plans to tighten regulations on labelling and advertising for formula milk for infants up to 12 months.
Most mothers said this is unlikely to affect how they buy formula milk, as they rely more on word of mouth and online reviews.
Still, housewife Melissa Lee, 22, welcomed the move. "Some companies claim that they added ingredients mentioned in the label, but it turned out to not be true.
"I hope the authorities would visit the factories and research the milk products."
But while Senior Minister of State for Trade and Industry Koh Poh Koon said on Monday that "cheaper (milk) options are no less nutritious", it may take some time before parents believe that.
Said Ms Lee, who spends about $190 a month on Dumex milk for her 16-month-old daughter: "I will not choose the cheaper brands... If they all meet the nutritional needs of infants, then why the price difference?"