Inclusion Criteria:  Maternal age ≥ 18 years and ability to give informed consent. Singleton gestation Ultrasound examination that confirms or revises the EDD before 14 weeks of gestational age Gestational age ≥ 35 weeks' gestation Normal aneuploidy screening (1st trimester screening, 2nd trimester screening, integrated screening, NIPT) when performed Spontaneously conceived pregnancy (i.e the current pregnancy is not the result of in vitro fertilization)  Exclusion Criteria:  Fetal chromosomal or genetic abnormalities if invasive prenatal diagnosis is performed Fetal malformations or soft markers identified on fetal anatomy survey Episodes of uterine bleeding after 24 weeks gestation. Unobserved self-reported bleeding with confirmed intact pregnancy on ultrasound after the bleeding episode is not an exclusion criteria. Uterine/placental abnormalities including uterine malformations (i.e bicornuate uterus, didelpus uterus), abnormal placentation (placenta previa, accreta, percreta), uterine fibroids. Cerclage in the current pregnancy History of intrauterine fetal demise History of fetal growth restriction or birth weight > 4Kg in a previous pregnancy Fetal isoimmunization or alloimmunization Fetal demise in previous pregnancies Cancer (including melanoma but excluding other skin cancers). Dysplastic or pre-neoplatic conditions such as cervical intraepithelial neoplasia are admissible. Endocrine disease including thyroid disease (recently diagnosed or whose medication dose is not stable), adrenal disease, diabetes mellitus (pregestational and gestational). Renal disease with altered renal function (creatinine > 0.9, proteinuria > 300 mg/24 hour) Epilepsy or other seizure disorder Any collagen disease (lupus erythematosus, scleroderma, etc.) Active liver disease (acute hepatitis, chronic active hepatitis, persistently abnormal liver enzymes). Liver disorders accounting for cholestasis (including cholestasis of pregnancy) if diagnosed prior to enrollment. Hematological disorder including alloimmune and isoimmune thrombocytopenia but excluding mild iron deficiency anemia (Hb > 9 gm/dl). Patients with sickle cell disease are excluded. Chronic pulmonary disease including asthma requiring regular use of medication and active TB. An asthma inhaler used on an as needed basis for a cold or an asthma attack is not considered regular use. Heart disease except mitral value prolapse not requiring medication Cardiovascular disorders: chronic hypertension, gestational hypertension or preeclampsia diagnosed prior to enrollment Infectious diseases: HIV, CMV, toxoplasmosis, parvovirus B19, HBV, HCV Chronic treatments with medications such as aspirin, steroids, anti-hypertensive agents, immunosuppressants, antineoplastic drugs. Prior laparoscopic or open uterine surgeries where the uterine cavity was entered (such as myomectomies) Resectoscopic myomectomies (prior resectoscopic polypectomies are not contraindications) Prior classical cesarean deliveries.