This is a serious spontaneous case, initially received from other health professional on 12-Mar-2019, concerning a female neonate patient. The patient's 32-year-old mother had no maternal and paternal history of major congenital malformations. The patient's mother had no history of offspring with major congenital malformations. The mother's obstetrical history included one full term live birth, 1 preterm live birth and 1 spontaneous abortion. The patient's mother historical conditions included bacterial/ yeast vaginosis (from 13-Apr-2018 to 27-Apr-2018) and historical drug included: Metrogel (from 16-Apr-2018 to an unspecified date). On an unspecified day the mother's underwent cervix cerclage procedure (reported as cerclage placed). The mothers did not use tobacco, alcohol or illicit drugs during pregnancy. The patient's mother current conditions included: cervical incompetence, anaemia, mild polyhydramnios and herpes simplex virus (HSV) infection. The mother's concomitant medication included Prenatal vitamins [minerals nos; vitamins nos] for pregnancy, Procardia [nifedipine] for cervical incompetence and ferrous sulfate for anaemia. The patient's mother last menstrual period (LMP) date was 18-Feb-2018. On 05-Apr-2018, the patient's mother underwent cystic fibrosis mutation analysis, hemoglobin electrophoresis and a prenatal test for spinal muscular atrophy, and no congenital malformations were found. On 13-Apr-2018, the ultrasound prenatal test was performed, and the results showed no congenital malformation. On 19-Jun-2018, the ultrasound prenatal test was performed, and the results showed no congenital malformation. On 03-Oct-2018, at gestational age of 32-weeks, the foetus was exposed to FLUCELVAX QIVc (influenza vaccine, subunit influenza virus vaccine polyvalent, cell-culture-derived, route of administration: transplacental, batch number: 252664, dose, anatomical location and expiry date: not reported) (explicitly coded as foetal exposure during pregnancy) for an unknown indication. On 09-Oct-2018, the patient's mother underwent ultrasound prenatal test and the results showed no congenital malformation. On 16-Oct-2018, the patient's mother had preterm labor for which she received nifedipine and Makena (hydroxyprogesterone caproate) and on 29-Oct-2018 the patient's mother developed herpes simplex virus infection for which she received Valtrex (valaciclovir hydrochloride). 1 month and 10 days after the vaccination, the patient's mother delivered a female neonate at 37.1 weeks gestation by vaginal method. The neonate's birth weight was 2194 grams, head circumference was 30.5 cm and body length were 48.3 cm. The Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) scores were 5 (one minute), 9 (five minutes) and 9 (10 minutes). At the time of delivery, no pregnancy complications were reported. The mother's estimated delivery date (EDD) was reported as 03-Dec-2018. The outcome of the event low birth weight was not reported. This case was linked to 201902637 (mother case).; Reporter's Comments: A female neonate patient with mother's history (gestational history: 1 full term live birth, 1 preterm live birth and 1 spontaneous abortion; historical conditions: bacterial/yeast vaginosis and cervix cerclage procedure; current conditions: herpes simplex virus infection, cervical incompetence, anaemia and mild polyhydramnios) was considered as low birth weight baby, one month and 10 days after administration of Flucelvax QIV vaccine at 32 weeks of gestation (explicitly coded as foetal exposure during pregnancy). The neonate was considered as low birth weight baby delivered by vaginal method at 37.1 weeks of gestation. Considering there is no evidence for a biological mechanism that could cause the event, multiple maternal risk factors, significant gestation history, the event was assessed as not related to the suspect vaccine. The drugs administered during pregnancy (nifedipine, valaciclovir and metrogyl) further confound this case. The decision to administer a vaccine during pregnancy is related to medical decision making by the mother and her physician and is not related to any property of the medication. The event foetal exposure during pregnancy was assessed as not related considering the intended use of the vaccine. The company assessed the event 'low birth weight as serious (medically significant).