This is a serious spontaneous case, initially received from other health professional on 25-Mar-2019, concerning a male neonate patient. The patient's mother was a 21-year-old female of body mass index: 62.8, height 66 cm and weight 389 pounds. The patient's mother had 2 previous pregnancies in which one was full term live birth and the other one was a preterm live birth with no birth defects. The patient's mother had no history of offspring with major congenital malformation. Also, the patient's mother had no maternal or paternal history with major congenital malformations. The last menstrual period (LMP) date of the patient's mother was 18-Apr-2018. The type of pregnancy was multiple (twins). The pregnancy status of the patient was collected, and no pregnancy complications were noted. The paternal age was reported as 20 years. The patient's mother had a prior history of use of marijuana during current pregnancy. The patient had not used tobacco or alcohol during her current pregnancy. The mother's historical conditions included nausea, vomiting, chlamydia, vaginitis and candidiasis. The mother's historical drugs included Phenergan (promethazine) and Zofran (ondansetron) for nausea and vomiting, azithromycin for chlamydia, Metrogel for vaginitis and Terazol (terconazole) for candidiasis. The mother's current conditions included anaemia and hypertension since an unspecified date. The mother's concomitant medication included Prenatal vitamins (minerals nos, vitamins nos) for healthy pregnancy and ferrous sulfate for anaemia. On 19-Jun-2018, the patient's mother had prenatal tests which included spinal muscular atrophy, cystic fibrosis and haemoglobin electrophoresis and no major congenital malformations were noted. On 05-Jul-2018, the patient's mother had undergone ultrasound scanning and no major congenital malformations were noted. On 31-Jul-2018, the patient's mother had undergone ultrasound scanning and quadruple screening and no major congenital malformations were noted. Approximately at 23 weeks gestation, on 01-Oct-2018, the patient's mother received FLUCELVAX QIVc [route of administration, batch number: 252664, dose, anatomical location and expiry date: not reported] for an unknown indication and the foetus was exposed to FLUCELVAX QIVc via transplacental route (explicitly coded as fetal exposure during pregnancy). On 16-Nov-2018, the patient's mother had undergone ultrasound scanning and no major congenital malformations were noted. On 28-Nov-2018, 1 month and 27 days after vaccination, the patient's mother developed haemorrhoids. On 05-Dec-2018, 2 months and 4 days after vaccination, the patient's mother developed dermatologic cutaneous abscess. The patient's mother was treated with Anusol HC [hydrocortisone acetate, dose: 25 mg, frequency: twice a day (bid), route of administration: rectal, from 29-Nov-2018 to 14-Dec-2018], Colace [docusate sodium, dose: 100 mg, frequency: thrice a day (tid), route of administration: oral, from 28-Nov-2018 to 28-Dec-2018] and Proctofoam [pramocaine hydrochloride, route of administration: rectal, from 28-Nov-2018 to 29-Nov-2018] for haemorrhoids and Keflex [cefalexin, dose: 500 mg, frequency: twice a day (bid), route of administration: oral, from 05-Dec-2018 to 19-Dec-2018]. 2 months and 13 days after vaccination, the patient's mother gave vaginal live birth to male twin babies at 35.5 gestational week (reported as pre-term birth). One of the male neonate weighed 2270 grams (reported as low birth weight), length 41.9 cm and head circumference 31.1 cm. The APGAR (appearance, pulse, grimace, activity, and respiration) scores were 8 (one minute) and 9 (five minutes). No major congenital malformations (MCMs) were identified at birth. The other male neonate of weighed 2545 grams, length 44.5 cm and head circumference 33 cm. The APGAR (appearance, pulse, grimace, activity, and respiration) scores were 8 (one minute) and 9 (five minutes). No major congenital malformations (MCMs) were identified at birth. The mother's estimated delivery date (EDD) was reported as 13-Jan-2019 and corrected EDD as 23-Jan-2019. The outcome of the event low birth weight was not reported. This case is linked to 201902718 (twin baby case) and 201902716 (mother case).; Reporter's Comments: A male neonate patient experienced preterm birth and low birth weight, 2 months 13 days after maternal receipt of Flucelvax QIVc at approximately 23 weeks of gestation (considered as foetal exposure during pregnancy). Considering the past obstetric history of the mother (1 preterm live birth), multigravida, maternal use of illicit drug- marijuana in early pregnancy, maternal concurrent medical conditions (hypertension and anaemia) and history of infections (chlamydia, vaginitis, candidiasis and cutaneous abscess) during pregnancy, twin pregnancy and multiple concomitant medications, provide more plausible explanation rather than suspect vaccine. Hence, company assessed the events premature baby and low birth weight as not related to suspect vaccine. The event foetal exposure during pregnancy assessed as not related considering the intended use of vaccine. The company assessed the events 'premature baby' and 'birth weight low' as serious (medically significant).