Preterm Delivery A Heritable Trait

Analysis of preterm delivery (PTD) patterns among Mormon women in Utah and surrounding states indicates that genetics play a leading role in preterm delivery. If the genetic link holds, obstetricians can expect to see even higher rates of PTD in future years.

"Pre-term labor is already the number one problem in obstetrics today," said Kenneth Ward, MD, from the John A. Burns School of Medicine at the University of Hawaii at Manoa. "The preemies we saved in the last generation are now having their own preemies. There may well be a hitherto unappreciated genetic element at work."

Dr. Ward's population study on the heritability of PTD won second prize for papers on Current Clinical and Basic Investigation presented at ACM.

His group constructed a large genealogy database using more than 9,000 public domain data sources. The data set documents genetic relationships between about 17.5 million ancestors and 3.5 million descendants of the 10,000 or so Mormon individuals who settled Utah in the 19th century.

Dr. Ward used Mormon families because religion requires Mormons to track and document family history as accurately and as far into the past as possible. Generations of carefully documented marriages, both polygamous and monogamous, make it clear that many Utah residents are at least distantly related. Dozens of women who deliver preterm today share common ancestors.

On average, Dr. Ward said, today's Mormon residents of Utah are 23rd-degree relatives. But patients who deliver early are typically 8th-degree relatives. PTD is extremely common among mothers, daughters, and sisters. Almost 90% of patients in Utah who deliver before 36 weeks have grandparents who also evidenced PTD. A genome-wide scan is under way to isolate genes active in PTD.

"There are specific types of preterm labor that seem to breed true," Dr. Ward said. "There are many different genetic components at work here. We are probably talking about not just one gene but several. This population lets you track those polygenetic effects."

Ward K, Argyle V, Meade M, Nelson L. Heritability of preterm delivery. Obstet Gynecol. 2005;105 (4 suppl):5S