Background: Infection of the pregnant women in advanced period of pregnancy with any of the virus serotypes represents a danger not only for the developing fetus (e.g. fetal intrauterine retardation, fetal distress, oligoamniosis, etc.) but also for the pregnant woman who may develop respiratory and cardiovascular deficiency. We are interested to determine the peculiarities of the clinical evolution, of the flu diagnosis in pregnant women. Material and methods: The general study group consisted of 189 pregnant women which was divided into 2 clinical subgroups: L1, which included pregnant women with confirmed flu (n1=42) A(H1N1) and subgroup L2 of pregnant women with seasonal flu (n2=147). Results: The results of the examination of pregnant women for the flu virus’s DNK confirmed high frequency of pandemic flu in 2009, P<0.001. Since 2010-2017 the epidemiological state is reversed, with a high frequency of seasonal flu 81.6% (110), P<0.001. The development of both forms (seasonal and A (H1N1)) of the flu is presented by two clinical syndromes: toxico-infectious and catarrhal, P>0.05. The study of laboratory investigations of women with the flu demonstrates the presence of similar changes in the both groups: iron deficiency anemia 93 (49.2%); leukopenia 84 (44.4%); leukocytosis with neutrophilia 4 (2.1%); lymphocytosis 42 (22.2%), P>0.05. The most frequent complications of the pregnancy in pregnant women with the flu were premature delivery (early/late periods of pregnancy) – 15 (33.3}7.27) in L1 and in L2 – 35 (17.7}3.15), p<0.05, followed by intrauterine fetal infestation syndrome (fetal hypoxia, intrauterine fetal development retardation, oligoamniosis, placental dysfunction) – 33 (17.4%), p<0.05. Conclusions: Molecular methods of diagnosis to determine the virus serotype underlie the establishment of the definitive diagnosis of the flu. The risk of pregnancy disruption at various terms, premature birth, intrauterine fetus infestation syndrome are the most common complications in pregnant women with the flu in the study.