BACKGROUND: Ureaplasma urealyticum may cause female genital tracts infection and lead sterility, infertility and spontaneous abortion. But it still is not clear whether Ureaplasma urealyticum is one of the factors responsible for fetal malformation.OBJECTIVE: To investigate whether Ureaplasma urealyticum is one of the key factor responsible for fetal malformation.DESIGN: Non-randomized observation of compromised children and their parents with concurrent control.SETTING: The department of immunology and microbiology of a medical college.PARTICIPANTS: Totally 16 malformed fetuses(3 female and 13 male cases) and their parents were chosen from the family seeking pregnancy care in the Department of Gynecology and Obstetrics of the First Affiliated Hospital of Luzhou Medical College and Luzhou First People's Hospital from 1995 to 1997.METHODS: Ureaplasma urealyticum detection was performed in 16 samples of the umbilic blood of the malformed fetuses, sperms of the father, and cervical mucus of the mother who conceived the malformed fetus. The 11 couples positive for Ureaplasma urealyticum were treated with macrolides and aminoglycoside antibiotics and followed up for the outcome of the following pregnancy.MAIN OUTCOME MEASURES: The relation between Ureaplasma urealyticum infection and fetal malformation was examined.RESULTS: Totally 11 of the 16 umbilical blood samples(69% ) were positive for Ureaplasma urealyticum, and serological tests of parents in the 11 positive cases detected rubella virus, cytomegalovirus or Toxoplasma gondii antibodies, nor was abnormality found in chromosomal examination. The following pregnancies and delivery were followed up in 4 women, and the babies showed no functional or organic abnormities with good development till the age of 2 years.CONCLUSION: Female genital tract Ureaplasma urealyticum infection is related to fetal malformation, which provides evidence to support interventions of the occurrence of fetal malformation.