Polyhydramnois third trimester; Vaccine Exposure during pregnancy; This is a serious observational study case initially received on 12-Aug-2019, concerning a 22-year-old, adult female, pregnant subject  of body weight: 184 lbs, height: 65 inches and body mass index (BMI): 30, enrolled in a prospective observational safety study on pregnancy outcomes in women immunized with seasonal cell culture influenza trivalent (TIVc) or quadrivalent (QIVc) vaccine during pregnancy .  The subject didn't have previous pregnancies. On unspecified date subject's family history of major congenital malformation was collected and the subject had no maternal or paternal history with major congenital malformations.  The subject's last menstrual period (LMP) date was on 08-Jul-2018. The subject's current conditions included anxiety, depression, nausea, chlamydia, vaginitis and urinary tract infections. During the pregnancy subject used tobacco (8 cigarettes per day) but did not use alcohol or illicit drugs. The subject's concomitant medications included Zoloft (sertraline hydrochloride), Promethazine(promethazine), azithromycin, Metrogel (metronidazol) and Macrobid (clarithromycin). On unspecified date, the pregnancy status of the subject was collected, and no major congenital malformations were noted. The type of pregnancy was singleton.  On 17-Aug-2018, the subject underwent cystic fibrosis carrier, haemoglobin electrophoresis and spinal muscular atrophy screen no major congenital malformation noted.  On 24-Aug-2018 subject underwent ultrasound scan. No major congenital malformation noted.  On 29-Oct-2018, at 16 weeks of gestation, the subject was administered Flucevax Vaccine cell subunit QIV NVD [influenza vaccine, batch number: 252664, dose, route of administration, anatomical location and expiry date: not reported] (explicitly coded as vaccine exposure during pregnancy) for influenza immunisation. On the same day subject underwent first trimester screen and ultrasound scan and no major congenital malformation noted. On an unspecified date, during the third trimester, the subject developed polyhydramnios.  The subject's estimated date of delivery (EDD) and corrected estimated date of delivery (CEDD), both were reported as 14-Apr-2019.  The subject vaginally delivered a full-term, female neonate at 39.3 weeks gestation. The neonate's birth weight was 2892 grams, length 50,2 cm and head circumference 33,0 cm. The appearance, pulse, grimace, activity, and respiration (APGAR) score was 5 (one minute) and 10 (five minutes). It was reported that there were no major congenital malformations (MCM) identified at birth.   Company assessed case as serious (medically significant).  Company comment: The patient developed polyhydramnios, associated with Flu Vaccine Cell Subunit QIV NVD, administered at 16 weeks of gestation. The patient developed polyhydramnios on an unspecified date, during the third trimester. Chronology is plausible. The patient's medical history of chlamydia, vaginitis, urinary tract infection and multiple concomitant drugs used during pregnancy may have contributed to development of the event. However, causal role of the suspect vaccine cannot be totally excluded and is assessed as related for the event of polyhydramnios. The event of vaccine exposure during pregnancy was assessed as not related considering the intended use of the vaccine.; Reporter's Comments: The patient developed polyhydramnios, associated with Flu Vaccine Cell Subunit QIV NVD, administered at 16 weeks of gestation. The patient developed polyhydramnios on an unspecified date, during the third trimester. Chronology is plausible. The patient's medical history of chlamydia, vaginitis urinary tract infection and multiple concomitant drugs used during pregnancy may have contributed to development of the event. However, causal role of the suspect vaccine cannot be totally excluded and is assessed as related for the event of polyhydramnios. The event of vaccine exposure during pregnancy was assessed as not related considering the intended use of the vaccine.