Inclusion Criteria:  Women aged >18 years Singleton pregnancy Women who are willing and able to attend serial ultrasonographic examinations during the whole pregnancy Women willing to sign an informed consent  Exclusion Criteria:  Multiple pregnancies; more than one fetus Any maternal medical disease, including asthma, chronic hypertension, diabetes mellitus, heart disease, extracardiac anomalies, human immunodeficiency virus or hepatitis infection, immunological disorders, lupus, and thyroid disease Diagnosis of fetal malformations; fetus with a structural or chromosomal anomaly Fetus with Small-for-Gestational-Age (SGA) or intrauterine Growth Restriction (IUGR) (a fetal weight that is below the 10th percentile for gestational age) as determined through an ultrasound. Smokers or drug/alcohol women Women with breast implants were also excluded as implants commonly compromise the echocardiographic acoustic window Inability to understand and provide written informed consent