This is an observational study case, initially received from other health professional on 08-Nov-2018, concerning a 25-year-old adult female pregnant patient of body weight 131.4 lbs, height 63.3 inches and body mass index (BMI) 23.1, enrolled in a phase IV, prospective observational safety study on pregnancy outcomes in women immunized with AFLURIA QIV, a seasonal quadrivalent vaccine, during pregnancy. The subject had no maternal and paternal history of major congenital malformations. The subject's obstetrical history included two previous full-term live births and had no birth defects occurred in previous pregnancies. The subject's current condition included low platelets (since 05-May-2018). The subject's concomitant medication included PNV (meclozine hydrochloride, pyridoxine hydrochloride) for pregnancy. The subject's last menstrual period (LMP) date was 26-Feb-2018. The type of pregnancy was singleton. The subject did not use tobacco, alcohol or illicit drugs during pregnancy. On 05-May-2018, prenatal blood work up- platelet count was performed, and the count was 141,000. Along with that, haemoglobin electrophoresis and fibrosis mutation analysis were performed, and no major congenital malformation was noted. On 21-May-2018, Zika virus testing was performed, and no major congenital malformation was noted. On 18-Jul-2018, anatomical scan was performed, and no major congenital malformation was noted. On 25-Sep-2018, the subject received TDAP (diphtheria vaccine, pertussis vaccine, tetanus vaccine) for pregnancy. On 23-Oct-2018, at gestation age of 34 weeks (third trimester), the subject was administered Flu Vaccine Egg Split QIV CSL (Influenza Vaccine, batch number: YF41708, dose, route of administration, anatomical location and expiry date: not reported) (explicitly coded to vaccine exposure during pregnancy) for an unknown indication. On 06-Nov-2018, Group B Streptococcus Infection (GBS) culture was found to be negative and no major congenital malformation was noted. On 10-Dec-2018, ultrasound  amniotic fluid value (AFV) test was performed and no major congenital malformation was noted. On 11-Dec-2018, 1 month and 18 days after vaccination, platelet count was found to be 119,000, and no major congenital malformation was noted. On an unspecified date, after vaccination, the subject developed chronic kidney stones. At the time of this report, the subject had not recovered from the event chronic kidney stones and the outcome of the event low platelets was not reported. The estimated date of delivery was reported as 03-Dec-2018. Follow up received from other health professional on 17-Jan-2019: Added lab tests (platelet count, fibrosis mutation analysis, Group B Streptococcus Infection (GBS) culture and ultrasound  amniotic fluid value (AFV) test) in the patient tab. Added new event platelet count decreased in the event tab. The narrative was amended accordingly.; Reporter's Comments: A 25-year-old female pregnant subject with concurrent medical condition low platelets (1,41,000) developed chronic kidney stones, unspecified period after receipt of Flu Vaccine Egg Split QIV CSL during 34th week of pregnancy. Considering the no known biological mechanism for the event chronic kidney stones due to flu vaccine, the causality was assessed as not related to suspect vaccine. Also as the vaccine was given during 34th week of gestation and event reported as chronic, the causal role of suspect vaccine can be ruled out. The patient also experienced low platelets (1,19,000), 1 month 18 days post vaccination. Considering the plausible immunological etiology, and plausible temporal relationship the causal role of study vaccine cannot be ruled out. Hence, the causality assessed as related to study vaccine. The underlying low platelets is considered as confounding factor. The event drug exposure during pregnancy was assessed as not related to suspect vaccine considering the event as special situation. The company assessed the case as serious (medically significant).