Polyhydramnios 3rd trimester; Exposure during pregnancy; This is a serious observational study case, initially received from other health professional on 31-Jul-2019, concerning a 33-year-old, adult, female pregnant subject of body weight: 180 lbs, height: 62 inches and body mass index (BMI): 32.9, enrolled in a prospective observational safety study on pregnancy outcomes in women immunized with seasonal cell culture influenza trivalent (TIVc) and quadrivalent (QIVc) vaccine during pregnancy.  The subject's relevant medical history included a type 2 diabetes mellitus and hypertension. The subject's obstetrical history included six previous pregnancies in which there were four full term live births, two spontaneous abortions and there were no birth defects reported. The subject had no history of offspring with major congenital malformation and no relevant maternal and paternal medical history. The subject did not use tobacco, alcohol or illicit drugs during pregnancy. The concomitant medications of the subject included Prenatal vitamins (minerals nos, vitamins nos), Humalog (insulin lispro), Levemir (insulin detemir), Promethazine (promethazine) and Celexa (citalopram).   The subject's last menstrual period (LMP) date was 07-Jun-2018. The type of pregnancy was singleton and estimated delivery date (EDD) was 14-Mar-2019.   On 16-Aug-2018, the subject underwent cystic fibrosis mutation analysis and spinal muscular atrophy screen test and no major congenital malformation (MCM) was noted.  On the next day, 17-Aug-2018, the subject underwent ultrasound and no MCM was noted.  The subject had two more ultrasounds in September, first was on 04-Sep-2018 and the second was on 27-Sep-2018, also no MCM was identified.   On 04-Oct-2018, at gestational age of approximately 17 weeks, the subject was administered Flucelvax QIVc [Flu Vaccine Cell Subunit NVD, dose: 0.5ml, batch number: 252664, route of administration, anatomical location and expiration date: not reported] for immunisation to influenza virus (explicitly coded as vaccine exposure during pregnancy).  On unspecified date subject experienced pregnancy complications noted as polyhydramnios 3rd trimester.  On 22-Feb-2019, the subject vaginally delivered a live normal male neonate at 37.1 weeks gestation. The neonate's birth weight was 3062 grams, head circumference was 32.4cm, length 52.1cm. The appearance, pulse, grimace, activity, and respiration (APGAR) scores were 7 at one minute, 8 at five minutes. APGAR score was not reported for 10 minutes.   Company assessed this case as serious (medically significant).  The subject experienced polyhydramnios in 3rd trimester of pregnancy after vaccination with the suspect product Flucelvax QIVc (Flu Vaccine Cell Subunit NVD) at gestational age of approximately 17 weeks. Chronology is plausible. Medical history of type 2 diabetes mellitus and hypertension may have contributed to development of the event. Causality was confounded by therapy with multiple concomitant medications. Considering all the above mentioned, causal relationship between the suspect product and the event polyhydramnios is assessed as related and as not related per company conventions for exposure during pregnancy.; Reporter's Comments: The subject experienced polyhydramnios in 3rd trimester of pregnancy after vaccination with the suspect product Flucelvax QIVc (Flu Vaccine Cell Subunit NVD) at gestational age of approximately 17 weeks. Chronology is plausible. Medical history of type 2 diabetes mellitus and hypertension may have contributed to development of the event. Causality was confounded by therapy with multiple concomitant medications. Considering all the above mentioned, causal relationship between the suspect product and the event polyhydramnios is assessed as related and as not related per company conventions for exposure during pregnancy.