Harvard M.D. John Rock pioneered in vitro fertilization and the birth control pill. [Courtesty R. Achenbach]

IN THE 1920s medical science began making big advances in understanding infertility. Researchers discovered the hormones that regulate reproduction -- estrogen, progesterone and testosterone. Doctors also accepted a theory they had long resisted: that poor sperm counts in men could be a significant cause of infertility.

In 1944, Harvard researcher John Rock reported one of the biggest breakthroughs in fertility medicine: Rock's team fertilized four human embryos in a laboratory dish. While the embryos were never returned to the womb, this experiment was the first in vitro (Latin for "in glass") fertilization in US history.

Publicity over in vitro and other technological developments sparked a surge in demand for infertility services. In 1953 Good Housekeeping magazine described infertility as a scourge that science would soon vanquish.

Lillian Lauricella and her twin daughters, born in 1934 and conceived by artificial insemination using donor sperm.

"Until recently a barren woman, or a woman who had been unable to conceive, could only hide her heartache," the article reported. "Today she has a right to hope for children. In the past few years medical science has made great strides in treating infertility. Relatively few couples are hopelessly sterile." LISTEN

Childless women flooded Rock and other practitioners with letters desperate for help. But science had promised more than it could deliver -- ovarian stimulation drugs such as Clomid and Pergonal would not be widely available until the 1960s. The first American in vitro baby would not be born until 1981.

Part six: Making Babies for America