(FORTUNE Magazine) – Infertility specialists are constantly searching for new ways to lend nature a hand in the baby-making process. These days they seem most excited by a procedure called intracytoplasmic sperm injection (ICSI), which they describe as a major breakthrough for infertile men. ICSI requires just one sperm. And it doesn't have to be in Olympic shape. In cases where live sperm can't be found in a man's ejaculate, doctors can tap into his testes or sperm duct to find it. The sperm is captured by its tail and sucked through a tiny tube containing a viscous solution that slows its motion. Then it is injected into the center of an egg cell. When fertilization occurs, doctors transfer the embryo from a petri dish into the womb of its future mother, just as they do with in vitro fertilization (IVF). Dr. Zev Rosenwaks, head of the infertility program at New York Hospital-Cornell Medical Center, says the procedure -- developed in Belgium two years ago -- has significantly increased the ability of infertile men to father children. ICSI is the most recent development in the new field of microinsemination, which began in 1986 when a mouse sperm was inserted into the outer rim of a mouse egg. Microinsemination is important for men who have extremely low sperm counts or whose sperm are slow moving or malformed; these men are rarely helped by other infertility treatments. Even IVF, which was developed to address female infertility problems like blocked fallopian tubes, requires a minimum of 50,000 sperm to be released in the vicinity of an egg. It costs a bundle -- about $10,000 per attempt -- to make a bundle of joy using ICSI. And since the procedure is experimental, little, if any, of the cost is reimbursable under most insurance policies. Furthermore, because the technology is so new, it may take a few years before more than a handful of infertility centers are able to use it with any measure of success. In the U.S. the places to go for ICSI are the Genetics & IVF Institute in Fairfax, Virginia; Reproductive Biology Associates in Atlanta; and New York Hospital, which now employs one of the Belgian doctors who pioneered the technique. At least one out of four couples undergoing an ICSI procedure at these three clinics takes home a baby.