Sacrococcygeal teratoma; Foetal exposure during pregnancy; This is an observational study case from, initially received from other health professional on 20-Jul-2020, concerning a foetus of an unknown gender, whose mother was 25-year-old, female pregnant subject of body weight: 176 lbs, height: 64.8 inches and body mass index (BMI): 29.5, who was enrolled in, a prospective observational safety study.  The foetus' mother's past medical condition included gestational diabetes mellitus, while the foetus' mother's current medical conditions included obesity, anxiety and asthma.   The s foetus' mother's concomitant medications included unspecified vitamins as obstetrical supplement and unspecified inhaler for asthma.   The foetus' mother's obstetrical history included six previous pregnancies with two spontaneous abortions (reported as history of miscarriages) and four full term live births. The foetus' mother had no history of offspring with major congenital malformation (MCM). The foetus' mother had no relevant maternal and paternal medical history with MCMs. The foetus' mother did not use tobacco, illicit drug or alcohol during pregnancy.  The foetus' mother's last menstrual period (LMP) date was 10-Oct-2019. The foetus' mother's estimated delivery date (EDD) was 16-Jul-2020 and corrected estimated date of delivery (CEDD) was 05-Aug-2020. The type of pregnancy was singleton. The foetus' father was 31-year-old.   On 02-Dec-2019, the foetus' mother underwent ultrasound test and no MCM was noted.  On 09-Jan-2020, at gestational age of 13 weeks (calculated per LMP), the foetus' mother was administered Flucelvax QIVc (Flu Vaccine Cell Subunit QIV NVD) [influenza vaccine, subunit influenza virus vaccine polyvalent; dose: 0.5 ml, batch number: 261228, anatomical location, route of administration and expiration date: not reported] (explicitly coded as Foetal exposure during pregnancy') for influenza immunisation.   On the same day, the foetus' mother developed morning sickness and was treated with Bonjesta (doxylamine succinate, pyridoxine hydrochloride) at dose of one tablet, twice a day, via oral route of administration.   On 24-Jan-2020, the foetus' mother underwent first trimester screen and nuchal translucency. No MCM was noted.  On 03-Mar-2020, the foetus' mother underwent maternal serum alpha fetoprotein screening (MSAFP/serum markers) and second trimester screen. No MCM was noted.  On 13-Mar-2020, the foetus' mother underwent anatomy ultrasound and abnormal lower spine was noted. The foetus' mother was referred to Maternal Foetal Medicine.    On 01-May-2020, the foetus' mother underwent follow-up ultrasound and multicyst mass at the sacral area was noted. It was most consistent with Sacrococcygeal teratoma. Therefore, the subject was referred for foetal diagnosis and treatment. Diagnosis was Sacrococcygeal teratoma.  At the time of this report, the outcome of the event Sacrococcygeal teratoma was not reported.  Per company, the event Sacrococcygeal teratoma was considered serious due to the criteria of congenital anomaly and medical significance.  The reporter did not provide causality assessment to Flucelvax QIVc.  This case is linked to the 202001214 (the corresponding mother case).  Company comment: A pregnant subject was administered Flucelvax QIV at approximately 13 weeks of gestation. The subject underwent ultrasound and multicystic mass at the sacral area was noted in foetus and was most consistent with Sacrococcygeal teratoma, approximately two months after vaccination. Sacrococcygeal teratoma is the most common congenital tumour in the neonate. Although their embryonic origin is still uncertain, they are believed to arise early in gestation (at around the late second or early third week). Causal role of the suspect vaccine is assessed as not related due to implausible chronology. Foetal exposure during pregnancy assessed as not related per company's conventions.; Sender's Comments: A pregnant subject was administered Flucelvax QIV at approximately 13 weeks of gestation. The subject underwent ultrasound and multicystic mass at the sacral area was noted in foetus and was most consistent with Sacrococcygeal teratoma, approximately two months after vaccination. Sacrococcygeal teratoma is the most common congenital tumour in the neonate. Although their embryonic origin is still uncertain, they are believed to arise early in gestation (at around the late second or early third week). Causal role of the suspect vaccine is assessed as not related due to implausible chronology. Foetal exposure during pregnancy assessed as not related per company's conventions.