Introduction
In recent months and during the rapid outbreak of corona virus disease in 2019 (Covid-19) all around the world, many pregnant women, like other people, have been infected with this deadly virus. Nevertheless, no adequate data is available on the clinical characteristics, manifestations, outcomes, and complications of this virus in pregnancy. Physiological respiratory and non-respiratory changes during pregnancy can predispose pregnant women to COVID-19 infection and aggravate outcomes (1). Some physiological changes in pregnancy include decreased lung volume and functional residual volumes due to diaphragmatic elevations, airway edema, increased oxygen consumption, hyper coagulation state, and altered cell immunity. It seems that these physiological changes can potentially lead to severe pulmonary infectious diseases during pregnancy.In previous pandemics such as H1N1, pregnancy increased susceptibility to serious illnesses and higher mortality rates than the general population (2).A 2009 study found out that women with H1N1 were four times more likely to be hospitalized(3) and also maternal mortality rate from the SARS virus has been reported about 25% (4) Despite this background, the majority of reported cases of COVID-19 infection in pregnancy have been classified as mild features of the disease and not more severe than general population(5). Most previous studies on the virus during pregnancy have been devised in the form of retrospective studies, case reports and case series. In fact, available evidence on the effects of the virus on pregnant women is still insufficient and inconclusive and there is no consensus between the experts about the virus and pregnancy and also many questions have remained unanswered and need further investigation. With the advent of Covid-19 pandemic, a number of articles have been published about this virus and pregnancy mostly associated with China. At a time that the virus is spreading swiftly around the globe, there is an inevitably urgent need for some well-designed studies in different countries based on diverse nationalities in order to be able to deal with the virus in pregnant women based on strong and solid scientific evidence. Really as far as we know, there has not been any prospective study in this area. so we decided to design a prospective cohort study to compare maternal and fetal consequences of Covid-19-infected pregnancy with non-infected pregnancy.