Women who were very small babies at birth may be less likely to have babies themselves, according to study findings.

Swedish researchers found that women who weighed less than 3 pounds, 5 ounces (1500 grams) at birth were 26 percent less likely to give birth themselves by their mid-twenties.

Study author Katarina Ekholm of the University Hospital in Linkoping noted that women who were small at birth may have an “altered structure and/or function in the reproductive organs,” that somehow influences their ability to have children.

Alternatively, women who used to be small babies may have social or behavioral differences that somehow influence their pregnancies, she noted.

Indeed, a recent study showed that women who were very tiny babies were less likely to have intercourse, be pregnant, or have delivered a baby by the age of 20.

Why small babies may grow up to become less likely to give birth “is an important, yet difficult, question” to answer, Ekholm told Reuters Health.

Previous research has shown that women born prematurely or with very low birth weight have a higher risk of high blood pressure and type 2 diabetes. Some experts have also suggested that being a small baby can influence a woman’s fertility.

During the current study, reported in the American Journal of Epidemiology, Ekholm and her team followed 148,281 women born between 1973 and 1975 until 2001. A small percentage of the women were born before 37 weeks’ gestation, weighed less than 3 pounds, 5 ounces (1500 grams) at birth, or were small for their gestational age.

The researchers found that women who had a very low birth weight were 26 percent less likely to have given birth themselves. This trend was most apparent in women who were 25 and older.

Women who were premature, or very premature, also tended to be less likely to have given birth. It was “less clear” whether being small for gestational age affected women’s chances of giving birth, the authors note.

Ekholm stressed that individual women who are born prematurely should not believe they are doomed to struggle to give birth.

“Following the general guidelines for health in pregnancy - i.e. no smoking/alcohol and regular medical check-ups, etc. - is more important on the individual level than if one was born preterm,” Ekholm said.

SOURCE: American Journal of Epidemiology, April 15, 2005.