Received Pfizer booster at 3w6d gestation. I was not aware I was pregnant at time of receiving booster shot.; Miscarriage - pregnancy stopped progressing at 5w6d. Last menstrual cycle was 06Feb2022. Received Pfizer booster at 3w6d gestation. I was not aware I was pregnant at time of receiving booster shot.; This is a spontaneous report received from a contactable reporter(s) (Consumer or other non HCP). The reporter is the patient.  A 37-year-old female patient (pregnant) received BNT162b2 (BNT162B2), on 04Mar2022 at 13:00 as dose 3 (booster), single (Lot number: FJ6369) at the age of 36 years, in right arm for covid-19 immunisation. The patient's relevant medical history included: "Covid-19" (unspecified if ongoing), notes: If Covid prior vaccination: Yes. Date of last menstrual period: 06Feb2022. The patient was 5 weeks pregnant at the time of exposure to BNT162b2. The patient was 5 weeks pregnant at the event onset. The patient is expected to deliver a baby(s) on 13Nov2022. The patient took concomitant medications. Vaccination history included: BNT162b2 (prev dose product=COVID 19,, prev dose brand=Pfizer,, prev dose brand unknown=False,, prev dose lot number=EW0186,, prev dose lot unknown=False,, prev dose administration date=09Jul2021, prev dose dose number=2,, prev dose vaccine location=Right arm), administration date: 09Jul2021, when the patient was 36-year-old, for COVID-19 immunization; BNT162b2 (Prev dose product=COVID 19,, Prev dose brand=Pfizer,, Prev dose brand unknown=False,, Prev dose lot number=EW0186,, Prev dose lot unknown=False,, Prev dose administration date=01Jun2021, Prev dose dose number=1,, Prev dose vaccine location=Right arm), administration date: 01Jun2021, when the patient was 36-year-old, for COVID-19 immunization. The following information was reported: ABORTION SPONTANEOUS (medically significant) with onset 01Apr2022, outcome "recovering", described as "Miscarriage - pregnancy stopped progressing at 5w6d. Last menstrual cycle was 06Feb2022. Received Pfizer booster at 3w6d gestation. I was not aware I was pregnant at time of receiving booster shot."; MATERNAL EXPOSURE DURING PREGNANCY (non-serious), outcome "unknown", described as "Received Pfizer booster at 3w6d gestation. I was not aware I was pregnant at time of receiving booster shot.". The event "miscarriage - pregnancy stopped progressing at 5w6d. last menstrual cycle was 06feb2022. received pfizer booster at 3w6d gestation. i was not aware i was pregnant at time of receiving booster shot." required physician office visit and emergency room visit. The pregnancy resulted in spontaneous abortion (13Nov2022). The patient underwent the following laboratory tests and procedures: SARS-CoV-2 test: (28Apr2022) Negative, notes: Nasal Swab. Therapeutic measures were taken as a result of abortion spontaneous.  Clinical Information: facility type for vaccine was Pharmacy or Drug Store. The patient had no other vaccine in four weeks. Other medication in two weeks included Prenatal vitamins. AE treatment included ER visit, 8 doctor visits, D&C procedure. The patient had no known allergies and other medical history.  No follow-up attempts are possible. No further information is expected.