Wal-Mart is recalling about 643,000 Mainstays love seat and porch rocking chairs because poor construction and over-curvature of the chairs' runners can cause instability, imbalance, fracturing of the wood and tip-over during use, posing a falling hazard to consumers.

The retailer said it has received 45 reports of injuries, including a cut in the leg requiring 16 stitches, fractured ribs, a shoulder joint tear and one incident in which a pregnant woman began having contractions after the display chair in which she was sitting flipped over backward.

Many of the injuries occurred on display models in Wal-Mart stores.

The recall involves three models of rocking chairs, the Mainstays Love Seat Rocker (Model IT-13380) and the Mainstays Porch Rocker (Model IT-13379 and IT-13270).

The love seats are wooden, white and seat two people. The back support frame and the seat are made of slats.

The wooden porch rocker is sold in white and light brown and seats only one person.

They sit on curved runners. The model number is printed on the rocker’s packaging.

The rockers were sold at Wal-Mart stores nationwide and on Wal-Mart's Web site from April 2004 through March for about $50.

The love seats were sold from May 2004 through September 2005 for about $100.

Consumers should immediately stop using the rocking chairs and return them to Wal-Mart for a full refund.

Consumers can call Wal-Mart at (800) 925-6278 or visit the retailer's Web site for more recall information.