The third trimester is full of eager waiting for the birth of a child. Expectant mothers are filled with excitement and anticipation for the newest bundle of joy to join the family. Obstetricians monitor the pregnancy in an effort to make sure baby safely arrives. At this point, the fetal anatomy survey has been done and, most likely, no physical abnormalities have been found. During the third trimester, however, other complications may arise that may warrant close monitoring with ultrasound. The biophysical profile is a fetal ultrasound that is useful in assessing high-risk pregnancies.
Pregnancy Complications
The expectant mother's blood pressure is taken with each visit to the obstetrician. Some mothers have a history of chronic hypertension and are appropriately treated throughout the whole pregnancy. Others develop pregnancy-induced hypertension that most likely subsides after childbirth. Hypertension can contribute to a low amniotic fluid index, known as oligohydramnios, and decreased fetal growth. Sometimes, the growth is so restricted that it may be referred to as intrauterine growth restriction (IUGR).
Diabetic mothers have a different outcome with pregnancy. While some mothers have a history of diabetes, others develop diabetes only during pregnancy, a condition known as gestational diabetes. This can lead to an increased amniotic fluid index, known as polyhydramnios, and increased fetal growth. Diabetic pregnancies often produce large babies resulting from high blood sugar.
Some expectant mothers have both hypertension and diabetes. Other complications can include autoimmune disorders such as lupus. These complications can lead to fetal death. To determine the well-being of a fetus, an obstetrician may order a series of ultrasounds called biophysical profiles. The results of a biophysical profile may indicate the necessity for early delivery.
Biophysical Profile Protocol
The biophysical profile is an ultrasound exam that is used to measure fetal well-being. There is a list of criteria that the sonographer examines. The examination can last for a maximum of 30 minutes. Each criterion is assigned a score of 2 if met. If a certain criterion is not fulfilled within 30 minutes, a score of zero is assigned. The following criteria are assessed during a biophysical profile:
- Amniotic fluid index (AFI) – four pockets of fluid are measured; two pockets must measure 2 cm or more for a score of 2
- Fetal breathing – fetuses "practice breathing" by contracting and relaxing the diaphragm muscle; a score of 2 is assigned for fetal breathing lasting 30 seconds or more
- Fetal tone – the full extension and flexion of a limb such as opening and closing a hand
- Gross body movements – two or three episodes of movement such as squirming or kicking
There are a total of eight possible points for the ultrasound portion of the biophysical profile. The non-stress test (NST) is the fifth criterion and may not be necessary with an ultrasound score of 8. Including the NST, the BPP may have a maximum score of 10.
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