The purpose of this study is to evaluate the flow of oxygen and blood necessary for nutrient transfer across the placenta during the second and third trimesters in pregnancy in women who are obese before pregnancy compared to women who have an average weight before pregnancy.

This study will evaluate blood flow across the placenta by functional Magnetic Resonance Imaging (fMRI). The investigators hypothesize that there will be differences in placental oxygenation and blood flow among women with obesity as compared to those with normal weight.

Participants will be asked to complete:

• MRI in the second trimester (20-24 weeks)
• MRI in the third trimester (30-34 weeks)

Inclusion Criteria:

• Singleton pregnancy, less than 24 weeks gestation
• Pre-pregnancy BMI between 18.5 - 24.9kg/m2 or ≥30kg/m2

Exclusion Criteria:

• Asthma on controller medication
• Autoimmune Conditions
• Chronic Hypertension
• Claustrophobia
• Congenital Anomaly
• Pregestational Diabetes
• History of Bariatric Surgery
• HIV
• Ineligible for MRI (incompatible implanted medical device)
• Multifetal Gestation
• Smoking during pregnancy

Pregnant people at 20-24 weeks gestation. 15 obese (OB) women and 15 normal weight (NW) will be recruited to participate in the study.

OB is defined as pre-pregnancy body mass index greater than or equal to 30 kg/m2, and NW is defined as pre-pregnancy body mass index between 18.5-24.9 kg/m2 without comorbidities.