2.3. Follow-Up Study Design
BLOOD, RECRUITMENT
Participants in the follow-up study were the offspring of mothers who participated in the pregnancy study detailed above. Of the 350 women who completed the initial study, 172 consented to allow their offspring to participate in the follow-up study funded by the Thrasher Research Fund (HR#19461). Recruitment took place between 2009 and 2013. Inclusion criteria included offspring aged 3 years 0 months to 5 years 11 months (3–5 years old) born to mothers in the pregnancy study described above. These ages were chosen because of the validation of the Brigance developmental screening and its ease of use in the research setting. The follow-up age was not the same for all subjects because the offspring were born over several years, and the follow-up study was conducted over a 3-year period. Of the 172 initially enrolled in the follow-up study, 156 completed follow-up visits between 3 and 5 years old. Within this group, 22 children were 3 years old, 44 children were 4 years old, and 90 children were 5 years old.Blood samples were obtained from all offspring at birth. After birth, offspring were seen once a year for 1 h long follow-up visits. During these visits, blood samples were obtained to evaluate the total circulating 25(OH)D concentration. Additionally, offspring underwent yearly developmental testing using the Brigance Screen II, described below. Written informed consent was obtained from the parents/guardians for this study.