Anatomy: Fetus in Utero
The amniotic sac is a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with amniotic fluid (liquid made by the fetus) and the amnion (the membrane that covers the fetal side of the placenta), which protects the fetus from injury and helps to regulate the temperature of the fetus.
The anus is the opening at the end of the anal canal.
The cervix is the lower part of the uterus that projects into the vagina. Made up of mostly fibrous tissue and muscle, the cervix is circular in shape.
A fetus is an unborn baby from the eighth week after fertilization until birth.
The placenta is an organ, shaped like a flat cake, that only grows during pregnancy and provides a metabolic interchange between the fetus and mother. (The fetus takes in oxygen, food, and other substances and eliminates carbon dioxide and other wastes.)
The umbilical cord is a rope-like cord connecting the fetus to the placenta. The umbilical cord contains two arteries and a vein, which carry oxygen and nutrients to the fetus and waste products away from the fetus.
The uterine wall is the wall of the uterus.
The uterus, also called the womb, is a hollow, pear-shaped organ located in a woman's lower abdomen, between the bladder and the rectum, that sheds its lining each month during menstruation and in which a fertilized egg (ovum) becomes implanted and the fetus develops.
The vagina is the part of the female genitals, behind the bladder and in front of the rectum, that forms a canal extending from the uterus to the vulva.
Glossary of Terms Related to High-Risk Obstetrics and Maternal Fetal Medicine
3-D Ultrasound Evaluation
Technology that allows the baby's anatomy to be viewed in a three-dimensional perspective. It allows for assessment of organ size and shape. It aids in determining fetal weight.
, a thin needle is inserted through the mother's abdomen into the sac around the baby under sonographic guidance. A small amount of fluid is withdrawn and sent to a laboratory. Cells are cultured, and the baby's chromosome make-up is reported in approximately two weeks. In addition, the amount of a substance called AFP is determined, which gives information about some structural defects, such as spina bifida. The procedure is brief and causes minimal discomfort. It is a relatively safe procedure, with little risk to the pregnancy. Amniocentesis is recommended for women over the age of 35 or for women who have a family history of inherited disorders. It can be performed any time after 14 weeks of pregnancy, but it is generally recommended between 15 and 20 weeks.
Fetal Biophysical Profile (BPP)
The fetal biophysical profile
is another detailed test of fetal well-being that is generally performed after 28 weeks. It is a sonographic assessment of your baby's movement, tone, practice breathing and the amount of amniotic fluid present.
Fetal Doppler Velocimetry
allows us to assess the blood flow in the umbilical cord and even in fetal organs, including the brain, kidney and aorta. The information obtained is especially helpful in managing complicated twin pregnancies, growth-restricted fetuses and certain other high-risk pregnancies.
Fetal echocardiography is a specialized ultrasound of your baby's heart. It detects most congenital heart defects. It is recommended if your baby is at a higher risk for a defect than the risk in the general population. For example, you may be at a higher risk if you have a family history of congenital heart disease, if you have diabetes or if you are on certain medications.
First Trimester Evaluation
The purpose of this ultrasound is to document the location of the gestational sac, note the fetal heart beat and number of fetuses seen. It is also important to evaluate the anatomy of the uterus.
Multifetal Pregnancy Reduction
Multifetal pregnancy reduction is a procedure done under special circumstances to reduce the number of fetuses in multiple gestation in order to improve outcomes for both mother and child/children.
Non-Stress Testing (NST)
An NST is a test of fetal well-being. An electronic fetal monitor is placed on the abdomen and a tracing of the fetal heart rate is generated. It is a painless, safe and non-invasive test that takes approximately 30 minutes. This test is repeated weekly, twice a week or even daily, depending on the risk factors. If the test is not entirely reassuring, additional tests may be recommended.
Percutaneous Umbilical Blood Sampling (PUBS) or Cordocentesis
PUBS is a specialized test in which a sample of fetal blood is withdrawn from the umbilical cord under continuous sonographic guidance using a similar technique to an amniocentesis. Analysis of the blood can determine fetal chromosomal anomalies, some fetal infections and fetal anemia. Fetuses can be given blood or platelet transfusions through the cord as well.
Second and Third Trimester Anatomical Assessment
To evaluate the growth and development of the baby's organs, as well as to note the baby's position.
Ultrascreening/First Trimester Genetic Screening
This test is a screening test that assesses the risk of certain chromosomal abnormalities. It is a combination of an ultrasound examination and a blood test done between the 11th and 14th weeks of pregnancy. The ultrasound examination is a standard first trimester sonogram, but a specialized measurement called a nuchal translucency is obtained. The blood specimen is analyzed for two chemicals: free Beta-hCG (human chronic gonadotropin) and PAPP-A (pregnancy-associated plasma protein-A), which are normally found in the blood of all pregnant women. The results of the nuchal translucency, the blood test and the mother's age give a specific estimated risk for Down’s syndrome and Trisomy 18. If the test results show an increased risk, the patient has the option of having a CVS or amniocentesis.