Polyhydramnios; Foetal exposure during pregnancy; This is an observational study case, initially received from other health professional on 01-Apr-2020, concerning a foetal subject whose mother was 32-year-old, female, pregnant subject of body weight: 207 lbs, height: 69 inches and body mass index (BMI): 30.6, enrolled in a prospective observational safety study.  The subject's mother's current medical history included increased BMI, bicornate uterus and opioid addiction.  The subject's mother's concomitant medications included Prenatal vitamins (unspecified vitamins and minerals) for pregnancy and buprenorphine for opioid addiction.  The subject's mother's obstetrical history included four previous pregnancies, one with full term live birth and three spontaneous abortions. The subject's mother had no maternal or paternal history with major congenital malformations (MCMs). Also, the subject's mother had no history of offspring with MCM. The subject's mother did not use tobacco, alcohol or illicit drugs during pregnancy.   The subject's mother's last menstrual period (LMP) date was on 22-Aug-2019. The subject's mother's estimated delivery date (EDD) was reported as 28-May-2020, while corrected estimated delivery date (CEDD) was reported as 06-Jun-2020. The type of pregnancy was singleton. The subject's father age was not reported.  On 18-Oct-2019, the subject's mother underwent ultrasound and no MCMs were noted.  On 01-Nov-2019, the subject's mother underwent non-invasive prenatal testing (NIPT) and no MCMs were noted.   On 06-Jan-2020, the subject's mother underwent maternal serum alpha fetoprotein screening (MSAFP) and no MCMs were noted.  On 28-Jan-2020, at approximately 22 weeks of gestation (calculated per LMP), the subject's mother was administered Afluria QIV (Flu Vaccine Egg Split QIV CSL) [influenza vaccine, subunit influenza virus vaccine polyvalent, cell cultured derived; batch number: P100112488, dose, route of administration, anatomical location and expiration date: not reported] (explicitly coded as Foetal exposure during pregnancy') for an influenza immunisation. On the same day, the subject's mother underwent 20-week anatomy ultrasound, but results were not provided. Also, the subject's mother developed gastroesophageal reflux disease (GERD) and was treated with omeprazole at a dose of 20 mg, once daily, orally.  On 17-Feb-2020, the subject developed polyhydramnios.  At the time of this report, the subject did not recover from the event of polyhydramnios.  The event of polyhydramnios was considered as serious due to criterion of medical significance.  The causality assessment was not provided.  This case is linked to case 202002689, the corresponding mother's case.  Company Comment: Polyhydramnios was noted after foetal exposure to the suspect product, Afluria QIV. Subject's mother was administered vaccine at 22 weeks of gestation. The event was detected 20 days later. Chronology is plausible. The subject's mother's current medical history included increased BMI, bicornate uterus and opioid addiction. Causality was confounded. However, causal role of the suspect vaccine cannot be excluded and is assessed as unlikely related (defaults to "related" in the safety database for reporting purposes). Foetal exposure during pregnancy is assessed as not related per company's conventions.; Sender's Comments: Polyhydramnios was noted after foetal exposure to the suspect product, Afluria QIV. Subject's mother was administered vaccine at 22 weeks of gestation. The event was detected 20 days later. Chronology is plausible. The subject's mother's current medical history included increased BMI, bicornate uterus and opioid addiction. Causality was confounded. However, causal role of the suspect vaccine cannot be excluded and is assessed as unlikely related (defaults to "related" in the safety database for reporting purposes). Foetal exposure during pregnancy is assessed as not related per company's conventions.