The first trimester is an excellent time, however, to have the mother recount her history. It is also a good time to make decisions about the use of progesterone, which in weekly injections has been shown to reduce the incidence of preterm delivery, and to institute a serial monitoring program so that any changes may be detected before the patient presents with rapidly advancing preterm labor – i.e., before a clinical emergency.
Such dialogue and interaction emphasizes to me the importance of a team approach to first-trimester screening that involves the ob.gyn. physicians, well-trained sonographers, well-trained perinatal nurses, and perinatologists who specialize in high-risk maternal and fetal complications.
Prenatal screening is no longer an in-and-out assessment of two or three measures. That began to change more than 5 years ago with adoption of the first-trimester screening approach combining biochemistry and imaging. It continues to evolve as prenatal screening provides an even more thorough and comprehensive view of fetal, placental, and maternal function that allows us to thoroughly map out the care of our patients. For women who have normal pregnancies, this is incredibly reassuring. And for those with any kind of outlying results or overt complications, it provides a starting point for making the best of even the most challenging pregnancies.
At left, the narrow nuchal translucency and brightly echogenic nasal bone at 12 weeks' gestation reduce the likelihood of aneuploidy. At right, the fetus has a NT over 4 mm and nonvisualizing nasal bone. CVS on the second fetus revealed Down syndrome.
Source Images courtesy Dr. Christopher R. Harman
In another pair of fetuses appearing at 12 weeks' gestation for nucal translucency screening, tricuspid valve Doppler shows normal flow on the left. The fetus on the right has a large downward jet of tricuspid regurgitation, suggesting possible abnormalities; pulmonary stenosis was later diagnosed.
Source Images courtesy Dr. Christopher R. Harman
3-D blocks analyzed by tomographic section in a systematic approach yield a complete catalogue of anatomic cardiac landmarks in over 80% of fetuses at 12 weeks.
Complete endocardial cushion defect was diagnosed at 12 weeks. First trimester echocardiography was triggered by abnormal ductus venosus alone during routine screening.
Source Elsevier Global Medical News
The Evolution of Prenatal Assessment
It is astonishing how much obstetrics and maternal-fetal medicine have grown. There was a time not too long ago when obstetric care was primarily delivered to the mother, with the fetus being a hopeful beneficiary. We could listen to the fetal heart rate using the fetoscope, but access to the fetus for its early developmental analysis was otherwise off-limits; its growth and development were assumed as part of maternal-focused obstetric care.
The introduction of electronic fetal monitoring gave us the opportunity to see a recording of the fetal heart rate pattern – its rhythm, and its quality – and we used that as an indirect measure of fetal well-being. Subsequently, ultrasound became available, and we could then evaluate the anatomy of the fetus – though usually in the latter part of pregnancy – and appreciate the morphology and overall growth performance.
It was not until relatively recently that the focus of prenatal assessment has shifted to the first trimester. In large measure, this change has been consumer driven. Families have become very interested in the development of their unborn children, and that interest increasingly has centered on obtaining more information earlier on. Such demand has pushed physician scientists working in the field to adapt their technologies to the first trimester. Recent research has, in large measure, advanced in response to parental interests.
Fetal diagnosis in the first trimester was thus born of this great desire and has evolved to the point where, as stated in this month's Master Class, it is becoming the standard of care. The field of first-trimester fetal diagnosis now consists of a series of biochemical and biophysical assessments that can truly evaluate fetal well-being at the current time and can contribute to the prediction of later development and later fetal well-being, or more importantly, the loss of fetal well-being.
It is in light of this burgeoning field of first-trimester evaluation that we decided to develop a Master Class to review this new state of the art. I have invited Dr. Christopher R. Harman, an international expert in the field of ultrasound and Doppler technology, to serve as this month's guest professor.
Dr. Harman is professor and interim chair of the department of obstetrics, gynecology, and reproductive sciences at the University of Maryland, Baltimore, as well as director of the school's maternal-fetal medicine division. He will explain how research is honing in on a first-trimester platform of assessments that holds even more potential for predicting risks and complications than we realized with the first-trimester screening algorithm that took hold more than 5 years ago.