title: Pregnancy and contraceptive use among women participating in an HIV prevention trial in Tanzania.
abstract: OBJECTIVE
  Information on pregnancy rates and factors associated with pregnancy and contraceptive use is important for clinical trials in women in sub-Saharan Africa where withdrawal of investigational products may be required in the event of pregnancy with a consequent effect on sample size and trial power.
  
  
  METHODS
  A prospective cohort analysis of pregnancy and contraceptive use was conducted in Tanzanian women enrolled in a randomised placebo-controlled trial of herpes simplex virus-suppressive therapy with acyclovir to measure the effect on HIV incidence in HIV-negative women and on genital and plasma HIV viral load in HIV-positive women. The cohort was followed every 3 months for 12-30 months. Women at each visit were categorised into users or non-users of contraception. Pregnancy rates and factors associated with pregnancy incidence and contraceptive use were measured.
  
  
  RESULTS
  Overall 254 of 1305 enrolled women became pregnant at least once during follow-up (pregnancy rate: 12.0/100 person-years). Younger age, being unmarried, higher baseline parity and changes in contraceptive method during follow-up were independently associated with pregnancy. Having paid sex and being HIV positive were associated with lower risk of pregnancy. Uptake of contraception was associated with young age, being unmarried, occupation, parity and the number and type of sexual partners.
  
  
  CONCLUSIONS
  Data on use of contraceptive methods and risk factors for pregnancy can help to guide decisions on trial eligibility and the need for additional counselling. Mandatory reliable contraceptive use in study participants may be required to reduce pregnancy rates in studies where pregnancy is contraindicated.
authors.affiliation: Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel St., London WC1E 7HT, UK. deborah.watson-jones@lshtm.ac.uk
authors.forename: Aderonke
authors.initials: A
authors.lastname: Odutola
authors.forename: Kathy
authors.initials: K
authors.lastname: Baisley
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Hayes
authors.forename: Mary
authors.initials: M
authors.lastname: Rusizoka
authors.forename: Clare
authors.initials: C
authors.lastname: Tanton
authors.forename: Helen A
authors.initials: HA
authors.lastname: Weiss
authors.forename: John
authors.initials: J
authors.lastname: Changalucha
authors.forename: David A
authors.initials: DA
authors.lastname: Ross
authors.forename: Deborah
authors.initials: D
authors.lastname: Watson-Jones
mesh_terms: D000212:Acyclovir / Q000008:administration & dosage; D000293:Adolescent; D000328:Adult; D000998:Antiviral Agents / Q000008:administration & dosage; D015331:Cohort Studies; D003270:Contraceptive Agents / Q000008:administration & dosage*; D004363:Drug Utilization / Q000706:statistics & numerical data*; D005260:Female; D015658:HIV Infections / Q000517:prevention & control*; D006561:Herpes Simplex / Q000188:drug therapy; D006801:Humans; D010919:Placebos / Q000008:administration & dosage; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D013636:Tanzania; D055815:Young Adult
chemical_list: D000998:Antiviral Agents; D003270:Contraceptive Agents; D010919:Placebos; D000212:Acyclovir