Gestational thrombocytopenia; Vaccine exposure during pregnancy; This is an observational study case, initially received from other health professional on 08-Oct-2019, concerning a 17-year-old female pregnant subject of body weight: 201 lbs, height: 63.5 inches and body mass index (BMI): 35.0, 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's historical condition included anemia.  The subject's concomitant medications included Prenatal vitamins (minerals not specified (NOS) and vitamins NOS) for pregnancy.  The subject had two previous pregnancies of full term live births. The subject did not have any history of previous birth defect. The subject's family history had no maternal/paternal history of major congenital malformations (MCM).   The subject's last menstrual period (LMP) was on 01-Jun-2018. The subject was pregnant with twins. The subject's estimated delivery date (EDD) and corrected estimated delivery date (CEDD) was reported as 08-Mar-2019. The subject did not consume tobacco, alcohol and illicit-drugs.  On 11-Oct-2018, at gestational period of 19 weeks, the subject was administered Flucelvax QIVc [influenza vaccine, subunit influenza virus vaccine polyvalent, batch number: 252664, dose, route of administration, expiry date and anatomical location: not reported] (explicitly coded as Vaccine exposure during pregnancy') for an influenza immunisation. On the same day, the subject underwent ultrasound and Quad screen and no MCM was noted.  On 17-Jan-2019, the subject underwent ultrasound and no MCM was noted.  On 25-Jan-2019 and 30-Jan-2019, the subject underwent Non-stress tests and no MCM was noted.  On 07-Feb-2019 and 13-Feb-2019, the subject underwent ultrasound and no MCM was noted.  On 19-Feb-2019, the subject underwent Non-stress tests and no MCM was noted.  On an unspecified date (reported as 23-Feb-2019), the patient developed gestational thrombocytopenia. The corrective treatment was not reported.  On 22-Feb-2019, at gestational age of approximately 38 weeks, the subject delivered twins (two male neonates) by caesarean method. The first neonate's birth weight was 3175 g, head circumference was 34.3 cm and length was 48.3 cm. Appearance, pulse, grimace, activity and respiration (APGAR) score at one minute was 6, at five minutes was 9 and no data was reported for APGAR score at ten minutes. The second neonate's birth weight was 2778 g, head circumference was 35 cm and length was 49.5 cm. APGAR score at one minute was 7, at five minutes was 9 and no data was reported for APGAR score at ten minutes. No MCM was identified at birth. On the same day, the subject recovered from gestational thrombocytopenia.  This case was assessed as serious and the reporter did not provide causality assessment.; Sender's Comments: The subject experienced thrombocytopenia after vaccination with the suspect product Flucelvax QIVc. Reportedly, vaccination occurred during pregnancy. Chronology is plausible. Medical history of anaemia and pregnant state may have contributed to development of the events. Causal relationship between the suspect product and exposure during pregnancy is assessed as not related per company conventions. For the event thrombocytopenia, causal role of the suspect product cannot be totally excluded and is assessed as possibly related.