This is a serious observational study case, initially received from other health care-professional on 17-Jan-2019, concerning a 37-year-old, adult, pregnant subject of body weight 180.2 lbs, height 73 in and body mass index (BMI) 23.8, enrolled in a prospective observational safety study. The subject's obstetrical history included spontaneous abortion once in the past, 2 full term live birth and 1 preterm live birth. The subject's historical procedure included loop electrosurgical excision procedure (LEEP) (on an unspecified date in 2003). The subject had no history of offspring with major congenital malformation and no relevant maternal and paternal medical history. The subject's last menstrual period date (LMP) was reported as 03-Oct-2018 and type of pregnancy was singleton. The subject did not use tobacco, alcohol and illicit drugs during pregnancy. The subject's current condition included Hashimoto's disease (Hashimotos as reported). The subject's concomitant medication included prenatal vitamins for pregnancy and levothyroxine for Hashimoto's disease. On 21-Nov-2018, the subject underwent ultrasound dating which showed no major congenital malformation. On 05-Dec-2018, at gestational age of 9-weeks (first trimester of pregnancy) the subject was administered Flu Vaccine Egg Split QIV CSL [influenza vaccine, dose, batch number, route of administration, anatomical location, and expiry date: not reported] (explicitly coded as vaccine exposure during pregnancy) for an unknown indication. On 11-Dec-2018, the subject underwent prenatal blood work (PNBW) cystic fibrosis and ultrasound which showed no any congenital malformation. On 02-Jan-2019, the subject underwent non-invasive prenatal testing (NIPT) and first trimester screening which showed no major congenital malformation. On 01-Mar-2019, 2 months and 24 days after vaccination, the subject underwent ultrasound scan for cervical length check and was diagnosed with complete placenta previa where the edge of placenta was sitting inside internal cervical opening (ultrasound scan abnormal). The cervical length was noted as 49.2 mm. No major congenital malformations noted. On 06-Mar-2019, the subject underwent anatomic scan and cervical length was noted as 34.4 mm with no major congenital malformations. The subject's estimated delivery date (EDD) was reported as 16-Jul-2019. Follow up received from other health professional on 21-Mar-2019: The subject's historical procedure loop electrosurgical excision procedure (LEEP) was added in the patient tab.  Added the subject's prenatal tests- anatomic scan and ultrasound scan in the patient tab. Added two events placenta previa and ultrasound scan abnormal in the event tab. Hence, the classification special case with no AE' was deleted from the general tab. The case seriousness was upgraded from non-serious to serious. The narrative and case comment were amended accordingly.; Reporter's Comments: A 37-year-old pregnant subject was diagnosed with complete placenta previa, 2 month 24 days post vaccination after receipt of study vaccine (Flu Vaccine Egg Split QIV) at 9 weeks of gestation (considered as vaccine exposure during pregnancy). The diagnosis was confirmed by prenatal ultrasound abnormal. The maternal gestational history included 1 spontaneous abortion, 2 full term birth and 1 preterm birth. Time to onset is considered implausible. Also, the advanced maternal age and multigravida are considered as known risk factors. Hence, causality of event placenta previa assessed as not related to study vaccine. The decision to administer a vaccine during pregnancy is related to medical decision made by the mother and her physician and is not related to any property of the medication. Hence, the event vaccine exposure during pregnancy assessed as not related considering the intended use of the vaccine. The company assessed the event 'placenta previa' as serious (medically significant).