BackgroundLoss to follow-up (LTFU) is a cause of potential bias in clinical studies. Differing LTFU between study groups may affect internal validity and generalizability of the results. Understanding reasons for LTFU could help improve follow-up in clinical studies and thereby contribute to goals for prevention, treatment, or research being achieved. We explored factors associated with LTFU of mother-child pairs after inclusion in the ANRS 12140-Pediacam study.MethodsFrom November 2007 to October 2010, 4104 infants including 2053 born to HIV-infected mothers and 2051 born to HIV-uninfected mothers matched individually on gender and study site were enrolled during the first week of life in three referral hospitals in Cameroon and scheduled for visits at 6, 10 and 14 weeks of age. Visits were designated 1, 2 and 3, in chronological order, irrespective of the child’s age at the time of the visit. Mother-child pairs were considered lost to follow-up if they never returned for a clinical visit within the first six months after inclusion. Uni- and multivariable logistic regression were adjusted on matching variables to identify factors associated with LTFU according to maternal HIV status.ResultsLTFU among HIV-unexposed infants was four times higher than among HIV-exposed infants (36.7% vs 9.8%, p < 0.001). Emergency caesarean section (adjusted Odds Ratio (aOR) = 2.46 95% Confidence Interval (CI) [1.47-4.13]), young maternal age (aOR = 2.29, 95% CI [1.18-4.46]), and absence of antiretroviral treatment for prophylaxis (aOR = 3.45, 95% CI [2.30-5.19]) were independently associated with LTFU among HIV-exposed infants. Factors associated with LTFU among HIV-unexposed infants included young maternal age (aOR = 1.96, 95% CI [1.36-2.81]), low maternal education level (aOR = 2.77, 95% CI [1.95-3.95]) and housewife/unemployed mothers (aOR = 1.56, 95% CI [1.16-2.11]).ConclusionFailure to return for at least one scheduled clinical visit is a problem especially among HIV-unexposed infants included in studies involving HIV-exposed infants. Factors associated with this type of LTFU included maternal characteristics, socio-economic status, quality of antenatal care and obstetrical context of delivery. Enhanced counselling in antenatal and intrapartum services is required for mothers at high risk of failure to return for follow-up visits.Electronic supplementary materialThe online version of this article (doi:10.1186/s12889-015-1555-2) contains supplementary material, which is available to authorized users.

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Although most children included were treated before age 7 months, the initiation of therapy was delayed for more than 1 in 3. The period around HIV diagnosis is critical and should be better managed to reduce delays before cART initiation.

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