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Analysis of Cohort Data (Kenya PNC) Unintended Pregnancy. Weiwei Zhou, Isolde Birdthistle , Susannah Mayhew - on behalf of the Integra Team. Cohort datasets. Cohort: Kenya PNC (n=869) Four rounds: Baseline, 6 months, 16 months, 24 months Study group: Intervention, Comparison
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Analysis of Cohort Data (Kenya PNC)Unintended Pregnancy Weiwei Zhou, IsoldeBirdthistle, Susannah Mayhew - on behalf of the Integra Team
Cohort datasets • Cohort: Kenya PNC (n=869) • Four rounds: Baseline, 6 months, 16 months, 24 months • Study group: Intervention, Comparison • Facility: 6 (Intervention) + 6 (Comparison) • UID: Facility code + Interviewers’ code + Client No. • Question: Does integration affect the incidence of unintended pregnancy? • Method: Time to event (survival) analysis
Outcome: Event (unintended pregnancy) • Since the last time we saw you (x months ago), have you become pregnant? • Yes • No • Missing + (AND) = Event occurred Y = 1 • At the time you became pregnant with the last pregnancy, did you: • Want to become pregnant then; • Want to wait until later; • Not want to have any/more children? • Missing
Outcome: Event (unintended pregnancy) • Since the last time we saw you (x months ago), have you become pregnant? • Yes • No • Missing + (AND) Event did not occur Y = 0 = • At the time you became pregnant with the last pregnancy, did you: • Want to become pregnant then; • Want to wait until later; • Not want to have any/more children?
Outcome: Event (unintended pregnancy) • What did you do when you discovered that you were pregnant with your last pregnancy? • Nothing • Attempted to stop but not succeed, • Attempted to stop and succeed. If Y = missing, Y is considered as 1 = OR • How did you feel when you discovered you were pregnant with your last pregnancy? • Happy • Unhappy/disappointed • Felt nothing • other • Were you using a family planning method when you became pregnant with this last pregnancy? • Yes • No AND
Date of unintended pregnancy xx months R(x-1) interview date R(x) interview date xx months OR How many months pregnant are you? Miscarried/aborted R(x) interview date R(x-1) interview date = ( b – a )/2 a b OR Given birth R(x-1) interview date R(x) interview date 9 months
Time (from baseline interview date to event date) Baseline Round 1 Round 2 Round 3
Exposure 1) Study Group (Intervention and Comparison) 2) Baseline index (categorical, <1.5, >=1.5) 3) Averaged cumulative index (per day).
Exposure: cumulative index Blue circle: Event (size of circle=level of integration) Red/Green dot: Higher/Lower ACI exposure group
Analysis plan • Cox proportional hazards model • Univariate analysis • Multivariable analysis, Adjusted for: Demographic: age, education, religion, employment statutes, household income SES Fertility preference: number of children, desired additional number of children, want/when to have another child, also husband’s wish. Other: HIV status, any children died, numbers of pregnancies • Test of model assumption
Limitations and Conclusions • Index of visits to non-study clinics are not available. Mean index values of study clinics have been used. • Event doesn't have an uniform distribution, thus the averaged cumulative index may not represent daily/monthly exposure to clinics. • Interaction terms • Kenya PNC: No significant effect by using study group, baseline index, or cumulative index as exposure variable.