Fetal Age Study Health Article

KEY TERMS

Gestational diabetes—Diabetes that first occurs during pregnancy and resolves once the pregnancy is terminated.

Transducer—The external device or probe used in conjunction with the ultrasound machine. Applied on the outside of the abdomen with a special gel, it bounces sound waves into the area being visualized, and then sends the return waves back to the computerized ultrasound machine for interpretation and visualization on the monitor. A transvaginal transducer is inserted into the vagina in order to be closer to the structures being evaluated.

Trimester—The average length of pregnancy is 280 days. The pregnancy is often divided into three trimesters, as different fetal development takes place in each of the three time periods. The first trimester extends to 14 weeks, the second through 28 weeks, and the third until 40/42 weeks, or term.

perform the ultrasound, a transducer is placed externally to the mother's abdomen. Use of a special gel allows the transducer to glide over the surface of the abdomen during scanning. Because the abdomen is exposed, privacy should be provided either with the use of a curtain or with a closed door. The mother should be asked if she would like her partner or support person with her during the test. A comfortable room temperature and warmed transducer gel assist in putting the mother more at ease. A towel or cloth placed over the mother's clothes protect them from becoming wet from the gel.

Aftercare

When the test is completed, the abdomen should be wiped dry of the transducer gel. If the mother needed to consume water prior to the test, she may need to urinate. She may require assistance in getting up from the ultrasound table. If non-reassuring test results have been conveyed to the mother, she may need a health care professional to stay with her for emotional support and to answer questions.

Complications

Because a fetal age study is noninvasive and observational, no complications are anticipated. If the measurements were not obtained carefully, the wrong gestational age will be determined. Interventions undertaken based on inaccurate findings could be considered a complication or risk of the procedure.

Results

The biometric results obtained are compared with norms for size and age, in order to estimate fetal age. Results outside of the normal range may indicate an SGA or LGA fetus, and require additional evaluation. Biometry may be used later in pregnancy when the fetal age is unclear. In this case, serial measurements may be taken after a two-to three-week period. The fetal growth during this time period can be compared against normal growth rates to estimate the gestational age. Because of rapid periods of fetal growth, each gestational week is also broken down further into the number of days. For example, the fetus's weight and length at 27 1/7 weeks is different from that for a fetus of 27 6/7 weeks.

Health care team roles

The fetal age study is usually performed by an ultrasound technologist in the imaging department. Non-routine biometry testing may provoke maternal anxiety over her baby's well-being. The ability of the technician to provide a calm, professional environment can help put the mother at ease.

BOOKS

Burrow, Gerard N. and Thomas P. Duffy, Editors. Medical Complications During Pregnancy, 5th Edition. Philadelphia: W. B. Saunders Company, 1999.

Creasy, Robert K. and Robert Resnik. Maternal-Fetal Medicine, 4th Edition. Philadelphia: W. B. Saunders Company, 1999.

Cunningham, F. Gary, et al. Williams Obstetrics, 20th Edition. Stamford, CT: Appleton & Lange, 1997.

Scott, James. Danforth's Obstetrics and Gynecology, Eighth Edition. Philadelphia: Lippincott Williams & Wilkins, 1999.

Esther Csapo Rastegari, R.N., B.S.N., Ed.M.