Polyhydramnios; Foetal exposure during pregnancy; This is an observational study case, initially received from other health professional on 05-Mar-2020, concerning a foetus subject, whose mother was 27-year-old, pregnant female subject of body weight 176 lbs, height 65 inches and body mass index 29.3, enrolled in a prospective observational safety study.  The subject's mother's medical history included BMI high and pre-eclampsia.  The subject's mother's concomitant medications included Prenatal vitamins (minerals not otherwise specified (nos); vitamins nos) and Aspirin (acetylsalicylic acid), both for pregnancy.   The subject's mother had one previous pregnancy with one preterm live birth. The subject's mother did not use tobacco, alcohol or illicit drugs during pregnancy. Also, the subject's mother had no maternal or paternal history with major congenital malformations.   The subject's mother's last menstrual period (LMP) date was 12-Jun-2019, estimated delivery date (EDD) was 18-Mar-2020 and the corrected estimated date of delivery (CEDD) was not reported. The type of pregnancy was singleton. The subject's father's age was not provided.  On 21-Aug-2019, the subject's mother underwent ultrasound and non-invasive prenatal test (NIPT) and no MCM was noted.  On 05-Sep-2019, the subject's mother underwent nuchal translucency and no MCM was noted.  On 03-Oct-2019, the subject's mother underwent maternal serum alpha-fetoprotein (MSAFP) / serum markers and no MCM was noted.  On 06-Nov-2019, at 21 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, expiration date and anatomical location: not reported] (explicitly coded as Foetal exposure during pregnancy') for influenza immunisation. On the same day, the subject's mother underwent 20 weeks anatomy ultrasound and no MCM was noted.  On 10-Dec-2019, after vaccination, the polyhydramnios in foetus was noted. On the same day, the subject's mother developed anaemia and was treated with ferrous sulfate.   At the time of this reporting, the outcome of the event 'polyhydramnios' was not resolved.   The event of 'polyhydramnios' was assessed as serious due to criterion of medical significance, per company.  The reporter did not provide causality assessment.  This case is linked to 202002352 (corresponding mother case).  Company comment: A foetus subject developed polyhidramnios after his mother was vaccinated with the suspect product Afluria QIV for influenza immunisation. Reportedly, one month after vaccination, polyhydramnios in foetus was noted. Chronology seems plausible. The subject's mother's medical history included BMI high and pre-eclampsia. The subject's mother's concomitant medications included Prenatal vitamins (minerals not otherwise specified (nos); vitamins nos) and Aspirin (acetylsalicylic acid), both for pregnancy. The subject's mother had one previous pregnancy with one preterm live birth. With information presented, causality is assessed as possibly related for polyhidramnios. Foetal exposure during pregnancy is assessed as unrelated per company conventions.; Sender's Comments: A foetus subject developed polyhidramnios after his mother was vaccinated with the suspect product Afluria QIV for influenza immunisation. Reportedly, one month after vaccination, polyhydramnios in foetus was noted. Chronology seems plausible. The subject's mother's medical history included BMI high and pre-eclampsia. The subject's mother's concomitant medications included Prenatal vitamins (minerals not otherwise specified (nos); vitamins nos) and Aspirin (acetylsalicylic acid), both for pregnancy. The subject's mother had one previous pregnancy with one preterm live birth. With information presented, causality is assessed as possibly related for polyhidramnios. Foetal exposure during pregnancy is assessed as unrelated per company conventions.