Normal Pregnancy

What is the purpose of imaging procedures during a normal pregnancy?

• It is unclear whether all women should undergo ultrasound screening during a normal pregnancy. 
• Noted advantages of routine screening ultrasounds include, more accurate pregnancy dating, less frequent labor induction for post term pregnancy, detection of multiple gestation and fetal growth restriction, and identification of fetal malformations. 
• Many studies have conflicting conclusions regarding the utility and the detection rates for all of the aforementioned uses of routine ultrasound, which renders the issue still up for debate. 
• Currently, the American College of Obstetricians and Gynecologists does not recommend routine ultrasound in low-risk pregnancies.   

What is the imaging modality of choice during pregnancy and why?

• Ultrasound is the clinical modality of choice during pregnancy. 
• There is widespread use of sonography in obstetrics and notably it has great potential for identifying fetal abnormalities and for providing reassurance of fetal well-being. 
• Also, there have been no confirmed bad biological effects in mammalian tissue in the frequency range of ultrasound medicine. 
• In the low-intensity range, there have been no fetal risks shown in over 30 years of use.  

What are the findings of normal pregnancy?

• In the first trimester, a basic ultrasound examination includes, gestational sac location, embryo identification, crown-rump length, fetal heart motion, fetal number, uterus and adnexal evaluation. 
• In the second and third trimester, the ultrasound examination includes, fetal number, presentation, fetal heart motion, placental location, amniotic fluid volume, gestational age, survey of fetal anatomy, and evaluation for maternal pelvic masses.   

When would you consider imaging modality in the evaluation of pregnancy?

Estimation of gestational age by ultrasound

• Evaluation for confirmation of clinical dating for patients who are to undergo
  • elective repeat cesarean delivery
  • induction of labor
  • elective termination of pregnancy
• Evaluation of fetal growth when the patient has an identified etiology for uteroplacental insufficiency, such as
  • severe preeclampsia
  • chronic hypertension
  • chronic significant renal disease
  • severe diabetes mellitus
  • for other medical complications of pregnancy when there could be fetal malnutrition
• Vaginal bleeding of undetermined etiology in pregnancy
• Determination of fetal presentation when the presenting part cannot be adequately assessed in labor
• Suspected multiple gestation
• Adjunct to amniocentesis
• Significant uterine size/clinical dates discrepancy
• Pelvic mass detected clinically
• Suspected hydatidiform mole
• Suspected ectopic pregnancy
• Adjunct to special procedures
• Suspected fetal death
• Suspected uterine abnormality
• Intrauterine contraceptive device localization
• Ovarian follicle development surveillance
• Biophysical profile for fetal well-being (after 28 weeks gestation)
• Observation of intrapartum events (e.g. version/extraction of second twin, manual removal of placenta)
• Suspected polyhydramnios or oligohydramnios
• Suspected abruptio placenta
• Adjunct to external version from breech to vertex presentation
• Estimation of fetal weight and/or presentation in premature rupture of membranes and/or premature labor
• Abnormal serum (alpha-fetoprotein [AFP] value for clinical gestational age when drawn)
• Follow-up observation of identified fetal anomaly
• History of previous congenital anomaly
• Serial evaluation of fetal growth in multiple gestations
• Estimation of gestational age in late registrants for prenatal care