List of Articles
- First Trimester Ultrasound Applications
For at least 20 years, many researchers have advocated the use of ultrasound in general and transvaginal ultrasound in particular to identify anomalies in the first and early second trimester. Over that period, advances in transducer technology, faster computers, and deepening understanding of developmental anatomy have facilitated such use. Increasing reliance on first-trimester screening brings more and more women with gestations from 11 to 14 weeks to the obstetricianís office, providing an opportunity to expand the narrow viewing angle of the ultrasound probe from the nuchal area to the entire fetus. As time goes on, we may discover additional compelling reasons to shift the first fetal evaluation from the second-trimester to the first-trimester. In the meantime, we find no reason not to widen the viewing angle of transducer probes to assess fetal anatomy at the first-trimester scan. This document discusses evolving applications of first-trimester ultrasound. Scanning can be performed transvaginally or transabdominally, although the transvaginal route is preferred during the first-trimester, because of high-resolution images it yields. Clear images improve reliability and accuracy. However, at times, a combination of transvaginal and transabdominal scanning may be preferred. Both basic and advanced first-trimester ultrasound applications are discussed in this review.
- Doppler Ultrasonography in Obstetrics
The advent of sonography has changed the practice of obstetrics by providing a window to the womb through which the anatomic structure of the fetus can be evaluated. The addition of Doppler flow studies of maternal and fetal vessels has provided a tool where the physiology of the maternal-fetal unit can be assessed. This information can provide the physician and the patient with vital information for a subsequent approach to the pregnancy. The use of fetal Doppler blood flow studies has become common in the evaluation and management of pregnancies complicated by conditions such as suspected fetal growth restriction and red blood cell isoimmunization to guide intrauterine therapy and delivery. The most commonly assessed Doppler flow studies of the fetus are the umbilical artery and middle cerebral artery (MCA). Doppler flow studies of MCA are used in the assessment of the fetus at risk of anemia and growth restricted fetus.
- Ultrasound Screening of Neural Tube Defects
The prevalence of congenital anomalies of the central nervous system varies in different epidemiologic studies, mostly as a consequence of the type of ascertainment and the length of follow up. The clinical role of sonographic biometry of the fetal cranium is well established. Biparietal diameter, head circumference, and transverse cerebellar diameter are currently used for assessing gestational age and fetal growth and identifying cranial abnormalities. Anencephaly and spina bifida comprise the majority of neural tube defects. In the 20 plus years since maternal serum alpha-fetoprotein (MSAFP) was recommended in United States for the general population, significant changes in the use of ultrasound and better understanding of the factors that place a woman at increased risk of bearing a child with spina bifida (and thus a candidate for diagnostic testing and not screening) have changed the utility of MSAFP screening. Amniotic fluid evaluation of alpha-fetoprotein and the role of fetal surgery for neural tube defects (NTDs) are also discussed.
- Ultrasound Evaluation of Uterine Scar
Between 1996 and 2003 the cesarean delivery rate in the United States increased dramatically from21.2% to 27.1%. Over the same interval vaginal birth after cesarean birth (VBAC) has decreased from 28.3% to 10.6%. This decrease may be attributed to concerns regarding the risks during trial of labor, such as uterine rupture, estimated to occur in 0.3-4.0% of pregnancies with history of cesarean delivery. As the VBAC rate increased, so did the number of well-publicized reports of uterine rupture and other complications during trials of labor after previous cesarean deliveries. As a result, many physicians and hospitals have discontinued the practice altogether. This abrupt change in practice has contributed to the cesarean delivery rate in the United States increasing again, reaching an all-time high of 26.1% in 2002, while the VBAC rate has decreased by 55% to 12.6%. The risk for poor obstetric outcome in a subsequent pregnancy has been shown to be related to surgical technique, with classical cesarean delivery having the highest risk for rupture and lower segment incisions having a lower risk. Clinical significance of uterine scar dehiscence in women with previous cesarean delivery is also discussed.
- Ultrasound Evaluation of Fetal Growth
A number of interventions are available to reduce morbidity and mortality in fetuses with intrauterine growth restriction (IUGR); but these can only be implemented appropriately with timely diagnosis and monitoring. Prenatal diagnosis of these conditions can aid in decision making concerning the timing and route of delivery, thereby reducing perinatal risk. Regulation of fetal growth is multifactorial and complex. Optimal fetal development depends on genetically predetermined growth potential, and is modulated by fetal, maternal, placental, and environmental factors. The role of Doppler ultrasonography is also discussed. Abnormally small fetuses as a group have a relatively poor prognosis because some of the causes of subnormal size, such as inadequate supply of oxygen and nutrients through the placenta, chromosomal anomalies, and infections, adversely affect fetal outcome. Disturbances of fetal growth -- intrauterine growth restriction (IUGR) and macrosomia -- are associated with increased risk of perinatal morbidity and mortality. Prenatal diagnosis of these conditions can aid in decision making concerning the timing and route of delivery, thereby reducing perinatal risk.
- Guidelines for Performance of the Obstetric Ultrasound
The purpose of this document is to present evidence regarding methodology, indications, benefits, and risks of obstetric ultrasonography in specific clinical situations. Sections of the document addressing physician qualifications and responsibilities, documentation, quality control, infection control and patient education are the recommendations of Women's Health and Education Center (WHEC). We are hopeful that this text will serve two purposes: to educate and to intrigue. Through the education process of the healthcare providers will help alleviate errors in diagnosis. Casual use of ultrasonography, especially during pregnancy, should be avoided. Before an ultrasound examination is performed, patients should be counseled about the limitations of ultrasonography for diagnosis.
- Sonographic Screening for Down Syndrome
Screening for Down syndrome is an important part of routine antenatal care. Significant advances have been made in antenatal screening for Down syndrome over the past few decades. The most common screening method in the United States involves the assessment of a combination of factors: maternal age, multiple second-trimester serum markers, and second-trimester ultrasonography. More recently there has been significant interest in first-trimester methods of screening, including screening for first-trimester markers and the sonographic measurement of fetal nuchal translucency. Invasive prenatal diagnosis for Down syndrome with amniocentesis or chorionic villus sample (CVS) is offered only to women of advanced maternal age (older than 35 years at delivery) or those who previously had an affected child or to women who has abnormal multiple-marker serum screening. The most efficient multiple-marker screening test in the second trimester is the "quad" screen, comprising alpha-fetoprotein (AFP), human chorionic Gonadotropin (hCG), unconjugated estriol (E3), and Inhibin-A. This approach yields sensitivities for Down syndrome of 67-76%. The purpose of the document is to summarize the current data and shift toward first-trimester screening for Down syndrome
- Ultrasound-guided Diagnostic Obstetrical Procedures
Ultrasound emerged as a major tool in medical imaging in the 1970s, and its impact has been very dramatic in obstetrics. The ability of sonography to detect fetal abnormalities prior to delivery and to direct minimally invasive therapy has revolutionized the field of obstetrics. The marked improvement in ultrasound image quality in recent years and the ability to store high quality digital images and video clips have enhanced ultrasound's role in obstetrics. The purpose of this document is to discuss various diagnostic procedures available and their indications. The most commonly used ultrasound-guided diagnostic obstetrical procedures are: 1) Amniocentesis; 2) Chorionic Villus Sampling (CVS); 3) Percutaneous Umbilical Blood Sampling.
- Principles of Genetic Counseling and Prenatal Diagnosis
The availability of prenatal diagnosis for a wide range of disorders has been a major advance in the area of reproductive genetics. Ultrasound has played a central role in the development of the various approaches to prenatal diagnosis. In addition, integration of a genetics-based prenatal diagnosis program with tertiary ultrasound has been shown to increase the accuracy of diagnosis when compared with ultrasound alone. The purpose of this document is to focus on the epidemiology of genetic defects and include a description of the various prenatal diagnostic procedures in use.
Women's Health & Education Center
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Dedicated to Women's and Children's Well-being and Health Care Worldwide