C-Section Has No Impact on Fracture Risk in Infants With Osteogenesis Imperfecta

OB/GYN News, Dec 15, 1999 by Barbara Baker

SAN FRANCISCO -- Cesarean section does not reduce the fracture risk of infants with osteogenesis imperfecta, investigators found in a retrospective review.

Nor does an operative delivery improve survival among those with severe disease, Dr. Peter H. Byers said at the annual meeting of the American Society of Human Genetics.

"The major indication for cesarean section of infants with osteogenesis imperfecta [OI] is therefore obstetric, not genetic," said Dr. Byers of the University of Washington, Seattle.

OI is a genetic collagen disorder caused by defective biosynthesis of type I collagen. It's associated with easily fractured bones and can range in severity from mild disease to a type that causes death in the perinatal period.

To determine whether mode of delivery influences outcome, Dr. Byers and his associates reviewed data on 167 women who delivered infants with OI. The diagnosis of OI was made prenatally in 39 women, almost all by ultrasound.

Ninety of the infants were delivered by cesarean section. The reason for an operative delivery was suspected OI in only 14 cases. Forty-eight were delivered operatively because of a nonvertex presentation and the rest because of other obstetrical indications.

Forty-four of 120 (37%) infants delivered at term had a breech presentation. The frequency of a breech presentation at term in the general population is 4%.

The percentage of neonates with new fractures diagnosed at birth did not vary by mode of delivery for all types of OI. Among infants with type I, the mildest form of OI, 2 of the 13 infants delivered by cesarean section and 4 of 16 delivered vaginally had new fractures. Similar patterns were seen for those with intermediate-severity disease, types III and IV.

All 50 infants with type II OI, the lethal type of disease, had dozens of new fractures, regardless of the mode of delivery.

Infants with type II disease delivered by cesarean section were more likely to be alive at 1-3 days of life than those delivered vaginally, but mode of delivery had no impact on survival by 2 weeks of life. All infants in this group died, Dr. Edith Cheng, also of the university, said in an interview.