Prenatal surgery to repair myelomeningoceles significantly reduced the need for shunts at 1 year of age and improved children's motor function at age 30 months, compared with children who had surgery after birth, based on data from a randomized trial of 183 pregnant women.

The results, published online, reflect data from 158 children who were evaluated at 12 months of age and 134 children evaluated at 30 months. Data collection is ongoing.

Surgery to repair the opening in the spine is usually performed after birth, but data from animal studies suggest that prenatal surgery could result in fewer complications, said Dr. N. Scott Adzick of the Children's Hospital of Philadelphia and his colleagues.

In the Management of Myelomeningocele Study (MOMS), 183 volunteer women with singleton pregnancies were randomized to prenatal surgery before the 26th week of pregnancy or surgery for their infants after birth (N. Engl. J. Med. 2011 Feb. 9 [doi:10.1056/NEJMoa 1014379

The children were examined for two primary outcomes. The first outcome, at age 12 months, was patient death or the need for a shunt. The second outcome, at age 30 months, was a composite score of motor function and brain development. The score was based on the Bayley Scales of Infant Development II (BSID-II) Mental Development Index and the difference between each child's actual ability and their expected motor function based on the severity of their spinal defect.

Death or the need for a shunt was significantly less likely in the prenatal surgery group, compared with the postnatal surgery group (68% vs. 98%). The rates of shunt placement were significantly lower for the prenatal surgery group, compared with the postnatal surgery group (40% vs. 82%).

All the fetuses in the study suffered from hindbrain herniation, in which the base of the brain is pulled into the spinal canal.

But at 12 months, 36% of the children in the prenatal surgery group had no evidence of hindbrain herniation, compared with 4% in the postnatal surgery group. Infants in the prenatal surgery group also had lower rates of moderate or severe hindbrain herniation than did the postnatal surgery group (25% vs. 67%).

In addition, infants in the prenatal surgery group scored an average of 21% higher on measures of mental and motor function, compared with infants in the postnatal surgery group, with primary outcome scores of 149 vs. 123, respectively.

Infants who underwent prenatal surgery were born at a mean 34.1 weeks of pregnancy, compared with a mean 37.3 weeks of pregnancy for the postnatal surgery group.

Significantly more infants in the prenatal surgery group had respiratory distress syndrome, compared with the postnatal surgery group (21% vs. 6%).

In terms of secondary outcomes, children in the prenatal surgery group were more likely to be able to walk without crutches or other orthotic devices, compared with the postnatal surgery group (21% vs. 42%).

The mean age of the pregnant women was 29 years. Each fetus had a myelomeningocele located between the T1 and S1 vertebrae, evidence of hindbrain herniation, and a gestational age of 19.0–25.9 weeks.

Exclusion criteria included a body mass index of 35 kg/m

Approximately one-third of the women in the prenatal surgery group showed uterine thinning or an area of dehiscence at the time of delivery. Women undergoing prenatal surgery must understand that they will require a cesarean delivery for the current pregnancy and any future pregnancies, the authors added.

The study was sponsored by the National Institutes of Health.

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Major Step in the Right Direction

Although the results are promising, it is important to be cautious in generalizing the success of prenatal surgery for myelomeningoceles to a wider population, Dr. Joe Leigh Simpson and Dr. Michael F. Greene said.

“The study by Adzick et al. is a major step in the right direction, but the still suboptimal rates of poor neonatal outcome and high maternal risk necessitate the use of less invasive approaches if such procedures are to be widely implemented,” they said.

Results might be less successful for patients treated in centers that are not as experienced in the procedure, Dr. Simpson and Dr. Greene noted.

In addition, more research is needed to determine which fetuses are more likely to benefit from the surgery, and whether performing the procedure earlier in gestation would yield even better outcomes, they added.

DR. SIMPSON is at Florida International University in Miami, Fla., and DR. GREENE is at Massachusetts General Hospital in Boston. They made their comments in an accompanying editorial (New Eng. J. Med. 2011 [epub

doi: 10.1056/NEJMe1101228

Prenatal Spinal Surgery Improves Brain Function