2.1. Study Design and Population

The prospective study was carried out at the maternity ward of the Instituto de Medicina Integral Prof. Fernando Figueira (IMIP), a publicly funded reference hospital for assistance of high-risk pregnancy and childbirth, located in the city of Recife, the capital of Pernambuco state, Northeast region of Brazil. The city of Recife is a hyperendemic area of arbovirus transmission and it was considered the epicenter of outbreaks of Zika disease [24] and ZIKV-related microcephaly in Brazil [25]. During the study recruitment (October 2018 and May 2019), 8705 cases of dengue, 160 of Zika, and 675 of chikungunya were reported in the general population by the local surveillance system [26]. Moreover, a population-based serological survey conducted by our group in a similar period (August 2018 to February 2019) have found the prevalence of serological markers of recent ZIKV and CHIKV infection (IgM antibodies) of 1.2% (95% CI: 0.6–2.2%) and 4.4% (95% CI: 3.2–6.1%), respectively, in the women at the reproductive age (15–49 years old, n = 855) living in this setting (data not published).

We consecutively enrolled PW with gestational age ≥ 27 weeks, aged ≥ 15 years, resident in the metropolitan area of Recife, and who were admitted to the maternity ward due to obstetric complications, regardless of having reported signs or symptoms of arboviral disease during the current pregnancy. Screening for DENV, CHIKV, or ZIKV infections are not included in the routine exams of the health unit, unless requested by the attending physician. Obstetric complications included were obstetrical bleeding, placental abruption, premature labor, premature amniorrhexis, chorioamnionitis, oligohydramnios, gestational diabetes, gestational hypertension, pre-eclampsia or eclampsia, and HELLP syndrome. We excluded those PW diagnosed with cancer, diabetes mellitus and chronic hypertension before the current pregnancy, HIV infection, syphilis, TORCH (Toxoplasmosis, Syphilis, Varicella Zoster, Rubella, Cytomegalovirus and Herpes simplex virus), autoimmune diseases, decompensated chronic heart disease, hemophilia A and B, Von Willebrand disease, and continued use of antiepileptic drugs.