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Design and Overview of PIN1 & PIN2

The primary aims of the first two phases of the PIN Study were to examine the association of infection and vitamin C and preterm birth (PIN1) and other micronutrients including folate and iron and preterm birth (PIN2). The study procotols were similar for these two phases and are described together.

PIN1 and PIN2 included a cohort of pregnant women seeking services from prenatal clinics at the Wake County Human Services Department, WakeMed Medical Center/Wake AHEC, and UNC Hospitals. PIN1 women were recruited from the Wake County sites from February 1996 until June 1998. PIN1 recruitment began at the UNC site in August 1995 and continued as the only site for the PIN2 recruitment, which ended June 2000. Overall, 3,163 women were recruited with 402 preterm delivery cases (12.8%).

Women were recruited for enrollment in the cohort at 24–29 weeks gestation, and were asked to participate in the following activities:

  • Provide blood, urine, and genital tract specimens at the recruitment visit for assay of micronutrient levels in blood, cotinine and illicit drugs in urine, and assessment of bacterial vaginosis from the genital tract specimens.
  • Complete a telephone interview conducted in the subsequent two weeks to collect information on a variety of other potential determinants of preterm birth, including use of tobacco, alcohol, and illicit drugs, symptoms of infection during pregnancy, physical exertion, and employment. The PIN2 protocol added a section on use of prenatal vitamins, multivitamins, and other vitamin and mineral supplementation.
  • Complete a self-administered diet inventory given to participants at recruitment.
  • Complete a self-administered psychosocial assessment, given participants at recruitment. This component was added in November 1996.

The study included a case-cohort component, in which a subcohort was randomly selected prior to recruitment. The automated tracking system randomly select the subcohort in a one-to-one ratio to preterm cases delivering at 35–36 weeks gestation and a two-to-one ratio for cases delivering prior to 35 weeks gestation. The randomization resulted in a subcohort of 29% of the full cohort of recruited women (925 women), some of whom went on to deliver preterm.

Most specimens were collected and stored for all recruited women but assayed only for women who delivered preterm or were in the subcohort.

Women who delivered preterm (<37 weeks) and women in the subcohort were approached in the hospital at the time of delivery to collect hair and urine specimens for assessment of cocaine and other illicit drugs. These women were re-interviewed within two months after delivery.

Following delivery, medical charts were abstracted.