Lyme disease and pregnancy outcome: a prospective study of two thousand prenatal patients.

Objective: The purpose of the study was to determine if prenatal exposure to Lyme disease was associated with an increased risk of adverse pregnancy outcome.

Study Design: Approximately 2000 Westchester County, New York, women completed questionnaires and had sera tested for antibody to Borrelia burgdorferi at their first prenatal visit and at delivery. Fetal death, birth weight, length of gestation at delivery, and congenital malformations were examined in relation to maternal Lyme disease exposure before and during pregnancy.

Results: Maternal Lyme disease or an increased risk of exposure to Lyme disease was not associated with fetal death, decreased birth weight, or length of gestation at delivery. Tick bites or Lyme disease around the time of conception was not associated with congenital malformations. Tick bites within 3 years preceding conception were significantly associated with congenital malformations, but this could have reflected reporting differences between exposed and unexposed women.

Conclusions: Maternal exposure to Lyme disease before conception or during pregnancy is not associated with fetal death, prematurity, or congenital malformations taken as a whole. We have not ruled out the possibility that exposure to Lyme disease as defined by maternal history increases the risk of specific malformations or has an effect if it is not treated. We have insufficient numbers of women who were seropositive at their first prenatal visit to determine if this subgroup of exposed women are at a moderately increased risk of having a child with a congenital abnormality. The low frequency of seroconversion at delivery in this endemic area suggests that preventive measures are being taken by obstetricians and patients.