Serial Third Trimester Abdominal Circumference and Amniotic Fluid Measurements Versus Routine Care

Inclusion Criteria:

- Maternal age of 18 at the time of consent

- Singleton gestation

- Ultrasound examination that confirms or revises the estimated date of delivery (EDD)
before 22 0/7 weeks of gestational age

- Gestational age ≥ 24 weeks gestation

Exclusion Criteria:

- Abnormal aneuploidy screening (1st trimester screening, 2nd trimester screening,
integrated screening, NIPT)

- Fetal chromosomal or genetic abnormalities

- Fetal malformations or soft markers identified on fetal anatomy survey

- Current pregnancy is a result of in vitro fertilization

- Documented uterine bleeding after 24 weeks gestation. Unobserved self-reported
bleeding with confirmed intact pregnancy on ultrasound after the bleeding episode is
not an exclusion criterion.

- Uterine/placental abnormalities including uterine malformations (i.e bicornuate
uterus, didelphus uterus), abnormal placentation (placenta previa, accrete, percreta),
uterine fibroids.

- Cerclage in the current pregnancy

- History of intrauterine fetal demise

- Fetal isoimmunization or alloimmunization

- History of medical complications such as:

- Cancer (including melanoma but excluding other skin cancers)

- 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 or proteinuria)

- Epilepsy or other seizure disorder

- Any collagen disease (lupus erythematosus, scleroderma, etc.)

- Active liver disease (acute hepatitis, chronic active hepatitis, persistently
abnormal liver enzymes)

- 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 tuberculosis (TB). An asthma inhaler used on an as needed basis (PRN)
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

- Liver disorders accounting for cholestasis

- Infectious diseases: HIV, Cytomegalovirus (CMV), toxoplasmosis, parvovirus B19