Low Placenta + small calcium buildup in heart; Pregnant at the moment of vaccination; Sore arm; Felt dehydrated even though she drinks lots of water; Fatigued; This spontaneous prospective pregnancy case was reported by a consumer and describes the occurrence of PLACENTA PRAEVIA (Low Placenta + small calcium buildup in heart) in a 30-year-old female patient (gravida 1, para 1) who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 045A21A and 042B21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Congestion nasal and Migraine. Concomitant products included FLUTICASONE PROPIONATE (FLONASE [FLUTICASONE PROPIONATE]) for Congestion nasal, MAGNESIUM and RIBOFLAVIN for Migraine, ASCORBIC ACID (VITAMIN C ACID), FISH OIL, COLECALCIFEROL (VITAMIN D [COLECALCIFEROL]) and PROBIOTICS NOS for Vitamin supplementation.   On 18-Mar-2021 at 4:30 PM, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 15-Apr-2021 at 4:45 PM, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. The patient's last menstrual period was on 16-Nov-2020 and the estimated date of delivery was 23-Aug-2021. On 18-Mar-2021, the patient experienced MATERNAL EXPOSURE DURING PREGNANCY (Pregnant at the moment of vaccination), PAIN IN EXTREMITY (Sore arm), DEHYDRATION (Felt dehydrated even though she drinks lots of water) and FATIGUE (Fatigued). On 05-Apr-2021, the patient experienced PLACENTA PRAEVIA (Low Placenta + small calcium buildup in heart) (seriousness criterion medically significant). The patient received mRNA-1273 (Moderna COVID-19 Vaccine) beginning around the  eighteenth week of the pregnancy. The delivery occurred on an unknown date. For neonate 1, The outcome was reported as Unknown. On 18-Mar-2021, MATERNAL EXPOSURE DURING PREGNANCY (Pregnant at the moment of vaccination) had resolved. On 19-Mar-2021, DEHYDRATION (Felt dehydrated even though she drinks lots of water) and FATIGUE (Fatigued) had resolved. On 21-Mar-2021, PAIN IN EXTREMITY (Sore arm) had resolved. At the time of the report, PLACENTA PRAEVIA (Low Placenta + small calcium buildup in heart) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 05-Apr-2021, Prenatal screening test: unknown (Inconclusive) Low placenta and small calcium buildup in the heart.. On 26-May-2021, Scan: unknown (Inconclusive) Placenta normal and small calcium build up in the heart still there..     mRNA-1273 (Moderna COVID-19 Vaccine) (Unknown) and mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosing remained unchanged.       The pregnancy history of the patient included one prior pregnancy of live birth in 30 Aug 2019. There has been no complications or acute illness during the current pregnancy. Concomitant medications reported as taken since conception included prenatal, probiotics and zyacc. On 26 Dec 2020, the patient had a positive pregnancy test. The first day of the patient last menstrual period was on 16 Nov 2020. The estimated date of conception was 04 Dec 2020. As for the current pregnancy the number of fetus included is one. Treatment information was not provided.  This report refers to a case of Maternal exposure with  mRNA 1273 during pregnancy with reported adverse event (placenta previa) and other non-serious adverse event. Per narrative the baby has been delivered and follow up has been requested to further evaluate the outcome of this pregnancy.   This case was linked to MOD-2021-235503 (Parent-Child Link).   See case MOD-2021-235503 for details regarding the child case.  Most recent FOLLOW-UP information incorporated above includes: On 24-Jun-2021: New lab test, dosage details, concomitant drugs and event were reported.; Sender's Comments: This report refers to a case of Maternal exposure with  mRNA 1273 during pregnancy with reported adverse event (placenta previa) and other non-serious adverse event. Per narrative the baby has been delivered and follow up has been requested to further evaluate the outcome of this pregnancy.