Low birth weight (infant 02- 2495 grams); Apgar score: one minute: 5; Foetal exposure during pregnancy; This is a serious spontaneous case reported by other health professional and initially received on 27-Jun-2019, concerning a male neonate patient.  The patient's mother was a 35-year-old female, who did not have any history of offspring with major congenital malformation. Also, the patient's mother had no maternal or paternal history with major congenital malformations. The patient's mother's obstetrical history included 3 previous pregnancies with 1 full-term live birth with no birth defects and 2 spontaneous abortions. The patient's mother didn't have a prior history of use of tobacco, alcohol or illicit drugs during pregnancy. The concomitant medications included Prenatal vitamins (minerals NOS, vitamins NOS) for pregnancy started prior conception.    The patient's mother's last menstrual period (LMP) date was 14-Sep-2018. The type of pregnancy was reported as multiple and the current pregnancy status was mono/Di twin gestation (as reported).  On an unspecified date (reported as 30-Jan-2017), the cystic fibrosis mutation analysis test and haemoglobin electrophoresis test were performed, and no congenital malformations were noted. On 18-Nov-2018, ultrasound test was performed, and no congenital malformation was noted.  On 28-Nov-2018, the foetus (gestational age: 10 weeks) was exposed to Afluria Quadrivalent (influenza vaccine, batch number: YF41708, route of administration: transplacental, parent route of administration, dose, expiry date and anatomical location: not reported) (explicitly considered as foetal exposure during pregnancy) for an unknown indication.   On 03-Dec-2018, the patient's mother underwent prenatal bloodwork and no congenital malformation was noted. On 05-Dec-2018, the patient's mother underwent chlamydia and gonorrhea culture with no congenital malformation noted. On 06-Dec-2018 and 31-Dec-2018, the patient's mother underwent ultrasound test and no congenital malformation was noted.   On 14-Jan-2019, the patient's mother underwent ultrasound test and no congenital malformation was noted.    at 37-week gestational age, the patient's mother gave live birth a male neonate (patient). The delivery method was by caesarean section (C-section). Neonate body weight was 2495 grams (coded as low birth weight baby), body length: 49.5 cm, head circumference was 38 cm and the appearance, pulse, grimace, activity, and respiration (Apgar) score: 5 at minute one (coded as Apgar score low) and 8 at minute five. The patient's mother also delivered a male neonate and the characteristics included body length: 54.6 cm, body weight was 3200 grams, head circumference was 36.5 cm and the appearance, pulse, grimace, activity, and respiration (Apgar) score: 8 at minute one, 9 at 5 minutes and at 10 minutes: no data was reported.   The patient's mother's estimated date of delivery (EDD) was reported as 21-Jun-2019.  This case was linked to case: 201806087 (mother case).; Reporter's Comments: A male neonate patient was delivered by caesarean section (scheduled) for twin pregnancy at 37 week of gestation, was noted to have low birth weight (2495grams) with APGAR score low at first minute of birth, 6 months 3 days after maternal receipt of Afluria Quadrivalent vaccine (considered as foetal exposure during pregnancy). The time to onset is considered implausible. Also, the twin pregnancy provide more plausible explanation rather than suspect vaccine for the reported events low birth weight and APGAR score low. Hence, causality assessed as not related to suspect vaccine. The event foetal exposure during pregnancy assessed as not related considering the intended use of the vaccine. The company assessed the case as serious (medically significant).