Polyhydramnios; Large for gestational age/Birth weight of 4025 g; Vaccine fetal exposure during pregnancy; This is an observational study case, initially received from other health professional on 01-Jun-2020, concerning a female foetal subject, whose mother was 34-year-old, pregnant, female subject of body weight: 182 lbs, height: 62 inches and body mass index (BMI): 33.3 enrolled in, a prospective observational safety study on pregnancy outcomes in women immunized with Afluria QIV, a seasonal quadrivalent vaccine, during pregnancy.  The subject's mother's past medical history included C-section. The subject's mother's current medical history included advanced maternal age and high BMI.  The subject's mother's concomitant medications included Prenatal (unspecified vitamins and minerals) for pregnancy.  The subject's mother's obstetrical history included one previous pregnancy with one full term live birth. The subject's mother had no history of offspring with major congenital malformation (MCM) nor relevant maternal and paternal history. The subject's mother did not consume tobacco, alcohol and illicit drugs during pregnancy.  The subject's mother's last menstrual period (LMP) date was 16-Jun-2019. The subject's mother's estimated date of delivery (EDD) was reported as 22-Mar-2020 and corrected estimated date of delivery (CEDD) was not reported. The type of pregnancy was singleton. The father's age was not provided.  On 12-Sep-2019, the subject's mother underwent MaterniT21 and no MCM was noted.  On 10-Oct-2019, at approximately 16 weeks of gestational age (calculated per LMP), the subject's mother was administered Afluria QIV (Flu Vaccine Egg Split QIV CSL) [influenza vaccine, batch number: P100112488, dose, route of administration, anatomical location and expiration date: not reported] (explicitly coded as 'Foetal exposure during pregnancy') for influenza immunization.  On the same day, the subject's mother underwent alpha-fetoprotein (AFP) test and no MCM was noted.  On an unknown date, an unknown amount of time after vaccination, polyhydramnios was noted and foetus was large for gestational age.  On, at gestational age of 38.1 weeks (as reported), the subject's mother delivered a female neonate by caesarean method. The birth weight of neonate was 4025 g. No data for head circumference and length were provided.  Appearance, pulse, grimace, activity and respiration (APGAR) score at one minute was 7 and at five minutes was 8. APGAR score for 10 minutes was not provided.  No MCM was identified at birth.  At the time of initial reporting, the outcome of the events polyhydramnios and 'large for dates baby'  was not reported.  Per company, the events polyhydramnios and 'large for dates baby' were considered serious due to the criterion of medical significance.   This reporter did not provide the causality assessment to Afluria QIV.  This case is linked to case 202003728 (the corresponding mother case).  Company comment: Reportedly, polyhydramnios was noted and foetus was large for gestational age an unknown amount of time after subject's mother received Afluria QIV. Chronology needs more clarification. However, causal role of the suspect vaccine was highly confounded by mother's medical history of advanced maternal age and high BMI. With information available, causality is assessed as not related. Foetal exposure during pregnancy is assessed as unrelated per company's conventions.; Sender's Comments: Reportedly, polyhydramnios was noted and foetus was large for gestational age an unknown amount of time after subject's mother received Afluria QIV. Chronology needs more clarification. However, causal role of the suspect vaccine was highly confounded by mother's medical history of advanced maternal age and high BMI. With information available, causality is assessed as not related. Foetal exposure during pregnancy is assessed as unrelated per company's conventions.