Transient laxity was documented around the end of pregnancy in a woman who had undergone anterior cruciate ligament (ACL) reconstruction 2 months before conception. This temporary laxity in the 3rd trimester and a few months postpartum corresponded to a time when substantial remodeling from large diameter to small diameter collagen fibers has been noted in the ACL graft ligamentization process. This is also a time of high levels of the hormone relaxin (member of the family of insulin-like growth factors), whose action in animals leads to dissociation of large collagen fibrils to smaller disorganized fibrils. The temporary laxity resolved. Careful observation of women who become pregnant in the first few months after ACL reconstruction is recommended.