Baby, you're in for a bumpy ride

Large study confirms harmful effects of small
uterine fibroids in pregnancy

By Phillipa Rispin

Fibroids are wild cards that can complicate a pregnancy � or cause much ado about nothing. Although it seems logical that uterine fibroids must have some effect on fertility, there's been surprisingly little definite information on them � until now. Researchers from the University of North Carolina are on the case. Their study on uterine fibroids should help us better understand these x factors.

At the 2004 annual meeting of the Society for Gynecologic Investigation in Houston in April, Dr Katherine Hartmann and colleagues presented the findings of a pilot study on the effects of fibroids on miscarriage, premature birth and fetal growth restriction.

"Fibroids are very common, as are these potentially devastating pregnancy outcomes," said Dr Hartmann. "Research evidence to inform clinical care is meagre. No studies have prospectively investigated these risks in a large cohort of women early in pregnancy where presence of fibroids was uniformly assessed using ultrasound imaging."

Dr Hartmann pointed out that previous studies usually looked at women with uterine fibroids "of concern" � fibroids at least 3cm or greater. Typically, smaller fibroids aren't considered a problem. "So the studies are flawed by inadequate classification of who has fibroids and who doesn't," she said. "In our pilot study of 1,600 women, we discovered that the majority of those who have fibroids were never informed about it." The pilot study showed fibroids in 170 subjects, who had a 55% increased risk of pregnancy loss. Surprisingly, the results showed that smaller fibroids were significantly more likely to lead to miscarriages than larger ones.

These findings have prompted the US National Institute for Child Health and Human Development to fund a larger study involving an additional 3,300 women from North Carolina. The study will also explore the influence of pregnancy and postpartum events on fibroid growth.

"With more than 5,000 women enrolled, the study will have the statistical power to more effectively examine the impact of race, maternal age and smoking status on pregnancy outcome in women with and without fibroids," Hartmann said.

Dr Togas Tulandi is one Canadian physician who's looking forward to the results. Dr Tulandi is a professor of obstetrics and gynecology and the Milton Leong Chair in Reproductive Medicine at McGill University.

"Hartmann's sample size will be very large, so the results will be valid epidemiologically," said Dr Tulandi. "But I'd be interested to know what kinds of fibroids it will be looking at. For instance, we know that submucosal fibroids (those in the uterine cavity) might affect embryo implantation, however, we're not sure how fibroids within the walls or on the surface of the uterus can affect these factors. We need more information from prospective, randomized studies."