Background: Air pollution and pregnancy outcomes have been widely described, however less is known about the temporal fluctuations and their health impact. Southwest communities in Bogota are the most vulnerable population to air pollution having a PM10 annual average of nearly 80 mcg/m3. Aim of the study was to identify potential adverse effects during advanced pregnancy according to the temporal patterns of air pollution in a deprived community in Bogota.Methods: A cross sectional study of women from 28 to 42 weeks of pregnancy that assisted at a second level hospital in Bogota's Southwest during 2016 was carried out. The sample included 126 women that were divided in two groups: a group of high levels of exposure that had their pregnancy during the dry season and the other one that had their pregnancy during the rainy season. PM10 was used as exposure variable and the outcomes were birth weight, systolic and diastolic blood pressure. PM10 level was adjusted by rainfall and temperature. Statistical analysis included t-test for independent samples and linear regression.Results: There were differences between mean PM10 during dry season (89 mcg/m3) and mean PM10 during the rainy season (66 mcg/m3) (p<0,05). Birth weight was significantly less (Mean difference=-388,1 gr, UI 95%: -507 a -268) in the group of high levels of exposure (2903kg ± 358,4) compared to the other group (3291kg±288,1). Such difference persisted during lineal regression after adjusting for temperature and cumulative rainfall (Beta=0.59 p<0.05). Other outcomes that were assessed did not show significant differences according to the levels of exposure.Conclusions: A temporal pattern of air pollution exposure and birth weight was observed in a polluted area of Bogota. Such findings have implications in maternal and child health and outline the importance of including these temporal variations on air pollution surveillance and control initiatives.