“Don’t worry, be happy” may sound like patronizing advice to a woman seeking help in having a baby but it may be just what the doctor ordered, according to research.

A team at the University of California San Diego found that women who worried about either the medical aspects or the cost of their assisted reproductive technology (ART) cases were less likely to become pregnant than women who are less concerned.

They studied 151 women seeking in vitro fertilization, also known as IVF, or another procedure called GIFT. The women filled out questionnaires about concerns relating to treatment side effects, surgery, anesthesia, pain recovery, finances, missing work, and having a baby.

Women worried about the medical aspects of the procedure had 20 percent fewer eggs retrieved and 19 percent fewer eggs fertilized than women who were less inclined to worry about it, the researchers report in this week’s issue of the journal Fertility and Sterility.

Patients who were very concerned about missing work had 30 percent fewer eggs fertilized, Hillary Klonoff-Cohen and colleagues found.

Those who were very concerned about how much the treatment cost were more likely to miscarry.

The results held even when age, race, smoking, type of infertility, number of previous attempts to become pregnant, and number of children already born were factored in.

“While no one has elucidated the physiological relationship between women’s concerns and the outcomes of their (assisted reproductive technology) cases, we know that stress has a number of negative systemic effects,” said Dr. Marian Damewood, President of the American Society of Reproductive Medicine, which publishes the journal.

“Worry about missing work and fears surrounding ART medical procedures are definitely stress-inducers. By the time patients arrive at ART, they’ve been through months or years of diagnosis, treatment and the emotional pain of infertility.”

She said fertility clinics should do more do ease the stress of their patients.