- The Washington Times - Sunday, July 6, 2003

CHICAGO (AP) — Girls born tiny and very prematurely are more likely than boys born prematurely to catch up with their peers in growth by age 20, a study found, but the researchers say the difference actually may favor boys.

While it generally has been considered desirable for premature infants to catch up in size with normal-weight infants, studies also have linked unusually rapid growth in childhood with an increased risk of obesity, heart disease and diabetes later in life.

Most of the catch-up growth in girls studied appeared to occur from ages 8 through 20. Although premature boys were half as likely as boys with normal birth weight to be obese, obesity rates were similar among premature girls and girls with normal birth weight.

“On the surface it appears that the male very low birthweight subjects might be at a disadvantage,” Dr. Maureen Hack and colleagues said. “However, we are more concerned about the future health of the very low birthweight females.”



The study appears in the July issue of Pediatrics, published today.

The study involved 103 boys and 92 girls born in the late 1970s at Rainbow Babies and Children’s Hospital in Cleveland, where Dr. Hack is a prominent researcher on prematurity.

On average, the infants were born about 10 weeks early and weighed less than 3 pounds. They were followed through age 20 and compared in growth with 208 normal-weight youngsters.

Prematurely born girls and girls with normal birth weight were both about 5 feet 3 inches at age 20. Girls born prematurely weighed on average about 143 pounds at that age, 6 pounds less than girls with normal birth weight.

In contrast, the premature boys were 5 feet 7 inches and 152 pounds at age 20 — one inch shorter and 24 pounds lighter than their counterparts with normal birth weight.

Only 7 percent of the premature boys were obese at age 20, about half as many as the boys with normal birth weight. But obesity rates were more similar among premature girls and those with normal birth weight — 15 percent and 18 percent respectively.

The boys born prematurely were generally sicker babies than the premature girls, echoing previous prematurity research, though significant prematurity complications including respiratory distress also occurred in the girls.

“We thought that neither of them would catch up,” Dr. Hack said, so “for the males, it’s not that surprising” that they were significantly smaller at age 20 than their peers.

The effects of female hormones that kick in when girls reach puberty may help explain their catch-up growth, Dr. Hack said.

Dr. Saroj Saigal, a prematurity researcher at McMaster University in Hamilton, Ontario, said the study echoes previous findings on growth differences between the sexes in adolescents but is one of the few to follow premature infants into adulthood.

It may be that rapid growth during puberty and adolescence is the most problematic, Dr. Saigal said.

“Perhaps we should strive for continuing weight gain and catch-up earlier on,” when premature babies are still hospitalized, she said. “We’re still not able to achieve that.”

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