This is an observational study case, initially received from other health professional on 08-May-2019, concerning a 33-year-old adult (as reported) female pregnant subject of weight 94 lbs, 64 inches height and body mass index (BMI) 16.1, enrolled in a prospective observational safety study. The relevant medical history of the subject included 1 previous pregnancy that was a full-term live birth with no reported birth defects. The subject did not have a history of offspring with major congenital malformation. On an unknown date, the subject's family history of major congenital malformation was collected, and the subject had no maternal/paternal history with major congenital malformations. The historical condition of the subject included female infertility and current conditions included herpes simplex of face and vitamin deficiency (unspecified). The concomitant medications of the subject included folic acid for vitamin deficiency, CITRANATAL BLOOM (as reported) (dosage: 90mg/1mg/12mcg/50mg, 1 tablet, orally, qd, start date: 07-Jan-2019, stop date: ongoing) for vitamin deficiency and Prenatal gummy (dosage: 1 tablet, orally, qd, start date: 20-Dec-2018, stop date: ongoing) for vitamin deficiency. The subject's last menstrual period date was 28-Oct-2018. The subject did not use tobacco, alcohol or illicit drugs during pregnancy. On an unknown date, the pregnancy status of the subject was collected, and pregnancy complication was noted as anemia of pregnancy. The type of pregnancy was singleton. On 20-Dec-2018, the subject underwent ultrasound scan and no major congenital malformation was noted. On 07-Jan-2019, at 10 weeks of gestation, the pregnant subject was administered Flu Vaccine Egg Split QIV CSL (batch number: YF41608, dose, route of administration, expiry date and anatomical location: not reported) for an unknown indication. On an unknown date, the subject experienced hyperemesis gravidarum and was treated with DICLEGIS at a dosage of 10mg/10 mg (as reported), one tablet, orally, as needed [prn], start date: 07-Jan-2019, stop date: ongoing. On 22-Jan-2019, nuchal translucency was done, and no major congenital malformation was noted. On 24-Jan-2019, first trimester screen and ultrasound scan were done, and no major congenital malformation was noted. On 25-Feb-2019, the subject underwent Maternal Serum Alpha-Fetoprotein (MSAFP)/Serum markers test, and no major congenital malformation was noted. On 15-Mar-2019 and 08-May-2019, the subject underwent ultrasound scans, and no major congenital malformation was noted. The outcome of the event hyperemesis gravidarum was not recovered. The subject's estimated and corrected estimated delivery date was reported as 04-Aug-2019. Reporter's Comments: A pregnant subject experienced hyperemesis gravidarum, unpecified period of time after receipt of Flu Vaccine Egg Split QIV at 10 weeks of gestation. Despite the lack of onset latency, considering the fact that treatment of hyperemesis gravidarum was started on the same day of vaccination and in addition, the first trimester of pregnancy provides more plausible explanation rather than study vaccine. The causality of the event hyperemesis gravidarum assessed as not related to study vaccine. Considering the intended use of vaccine, the event vaccine exposure during pregnancy assessed as not related. The company assessed this case as serious (medically significant).