Background
Antenatal care service which is among strategies to maintain maternal and fetal wellbeing is strongly recommended to be initiated early during pregnancy. To developing world where there is uncommon practice of pre-pregnancy care and support, timely commencement is crucial in getting potential benefits from some of the elements of the care. Therefore, we sought to assess timing and factors associated with the first antenatal care booking among pregnant mothers attending antenatal care clinics in Gondar town health facilities; North West Ethiopia.

Methods
Health institution based cross-sectional study was conducted among pregnant mothers from April to June 2012 in Gondar town. A total of 407 pregnant mothers were interviewed at exit from antenatal clinic by using structured and pre-tested questionnaire. Bivariate and multivariate data analysis was performed using SPSS for Windows version 16.0.

Result
The study indicated that 35.4% of mothers started antenatal care timely (in the first trimester of pregnancy). The mean time was 4.5 months (17.7 weeks) of pregnancy. Multivariate logistic regression analysis showed that: [(AOR (95% CI)) maternal age?=?25 (1.85 (1.10, 3.09)), age at marriage =20 years (2.21 (1.33, 3.68)), pregnancy recognition by urine test (2.29 (1.42, 3.71)), mothers who perceived the right time to start antenatal care within first trimester (3.93 (2.29, 6.75)) and having decision power to use antenatal care (2.43 (1.18, 4.99))] were significantly associated with timely commencement to antenatal care.

Conclusion
Timely entry to antenatal care was low in the study area. In order to improve the situation, it is important to provide community based information, education and communication on antenatal care and its right time of commencement. In addition, empowering women and implementing the proclamation designed for the age at marriage is mandatory up to the local level.