Immunological interference with the maternal recognition of pregnancy in primates.

If chorionic gonadotropin is involved, as part of the luteotrophic stimulus, in the maternal recognition of pregnancy in primates, then immunization against the beta subunit of hCG should prevent a conception going beyond the length of the normal cycle. Immunization against hCG-beta suppresses fertility in marmoset monkeys, baboons and rhesus monkeys, as long as the antibody titres remained high. As titres decline, however, female marmosets experience recurrent abortions interspersed with occasional live births. Young marmosets born to mothers with low circulating levels of antibody reach apparently normal sexual maturity. Immunization against hCG-beta subunit may have potential as a possible long-term method of fertility control in humans, but its reversibility needs further study. There is still a lack of basic knowledge of the functions of chorionic gonadotropin, especially now that its restriction to pregnancy seems improbable. Immunization against hCG may be valuable as a research tool with which to study the immunological relationships between mother and fetus during early pregnancy.