Perinatology, or Maternal and Fetal Medicine (MFM), is a sub-specialty
of obstetrics and gynecology dedicated to the care of women whose pregnancies
are or may be at high-risk. After completing a residency in obstetrics
and gynecology, MFM physicians complete a two- or three-year fellowship.
Below are some reasons women may seek care from a MFM.
Patients undergoing diagnostic or therapeutic procedures during pregnancy, such as:
- Comprehensive ultrasound
- Chorionic villus sampling
- Genetic amniocentesis, fetal surgery or treatment
Women with medical or surgical disorders, such as:
- Heart disease
- High blood pressure
- Preeclampsia (toxemia)
- Diabetes or other endocrine disorders
- Kidney or gastrointestinal disease
- Infectious diseases
Healthy women whose pregnancy is at markedly increased risk for adverse
outcome, such as:
- Abnormal AFP (alpha fetoprotein) blood test
- Twins, triplets or more
- Current or recurrent pre-term labor and delivery
- Premature rupture of membranes
- Recurrent pregnancy loss
- Suspected fetal growth restriction (baby not growing enough)
- Placenta previa
The most common reason women seek care from a MFM is prenatal screening
and prenatal diagnosis to detect birth defects such as neural tube defects,
Down syndrome, chromosome abnormalities, genetic diseases, as well as
spina bifida, cleft palate, Tay sachs disease, sickle cell anemia, thalassemia,
cystic fibrosis and fragile X syndrome. The testing can be invasive, such
as CVS (chorionic villus sampling), or non invasive such as ultrasound
or biochemical blood testing.
Genetic counseling is very important if you are over age 35, have a family
history of a genetic disorder or have had an adverse outcome in a previous
pregnancy. The counseling provides educational, informational and supportive
directives and can help guide you through the available prenatal testing
and explain the results.
Chorionic Villus Testing (CVS)
Chorionic villus sampling (CVS) is the removal of a small piece of placenta
tissue (chorionic villi) from the uterus during early pregnancy to screen
the baby for genetic defects. CVS can be done through the cervix (transcervical)
or through the abdomen (transabdominal). The techniques are equally safe
when done by a provider with experience, although miscarriage rates are
slightly higher when done through the cervix. The health care provider
will use ultrasound to pick the safest approach and as a guide during sampling.
An ultrasound is performed to determine the position of the uterus, the
size of the gestational sac and the position of the placenta within the uterus.
The transcervical procedure is performed by inserting a thin plastic tube
through the vagina and cervix to reach the placenta. The provider uses
ultrasound images to help guide the tube into the appropriate area and
then removes a small sample of chorionic villus tissue.
The transabdominal procedure is performed by inserting a needle through
the abdomen and uterus and into the placenta. Ultrasound is used to help
guide the needle, and a small amount of tissue is drawn into the syringe.
The risks of CVS are only slightly higher than those of an amniocentesis.
Possible complications include:
- Rh incompatibility in the mother
- Rupture of membranes
Signs of complications include:
- Excessive bleeding
- Excessive vaginal discharge
Amniocentesis is a test during pregnancy that removes a small amount of
fluid from the sac around the baby. The doctor will find the exact location
of the baby, usually by performing an ultrasound.
An area of skin on the belly is cleansed. The doctor inserts a long, thin
needle through the abdomen and into the womb (uterus). A small amount
of fluid is taken from the fluid-filled sac that surrounds the baby and
sent to the lab for analysis.
Risks are minimal, but may include:
- Infection or injury to the baby
- Leaking of amniotic fluid
- Vaginal bleeding
Non Invasive Testing
Nuchal Translucency (NT)
The NT test uses ultrasound to measure the clear (translucent) space in
the tissue at the back of your developing baby's neck. Babies with
abnormalities tend to accumulate more fluid at the back of their necks
during the first trimester, causing this clear space to be larger than
average. The test will screen for chromosome abnormalities and, when combined
with blood work, neural tube defects.
The NT scan must be done when you're between 11 and 13.5 weeks pregnant.
It is often combined with blood work. The final results of the test are
available after the blood work is completed. There are many different
blood tests available with the NT test. The physician or genetic nurse
will discuss the options and help guide you to the best test for you.
The results will be given as a positive or negative test, and will give
you numbers concerning your risk of a chromosome problem. If the test
is positive showing an increased risk for a chromosome problem, further
testing will be offered to you. A thickened measurement may also indicate
a cardiac defect.
Remember that a normal screening result (screen negative) isn't a guarantee
that your baby has normal chromosomes, but it does suggest that a problem
is unlikely. Likewise, an abnormal screening result (screen positive)
doesn't mean that your baby has a chromosomal problem — just
that he's more likely to have one. In fact, most screen-positive babies
turn out not to have a problem.
First trimester screening – Combined
The blood screen measures two pregnancy related hormones: hCG and PAPP-A.
A sample of your blood is taken between 11 and 13 weeks of pregnancy,
at the same time the NT ultrasound scan is performed.
The substances in your blood that are markers of Down syndrome are pregnancy
associated plasma protein A (PAPP-A); and human chorionic gonadotropin (hCG).
The specific ultrasound marker of Down syndrome is nuchal translucency
In pregnancies with Down syndrome, PAPP-A tends to be low, and NT and hCG
tend to be raised.
The values of these markers are used together with your age to estimate
the risk of having a pregnancy affected with Down syndrome.
The combined accuracy rate for the screen to detect the chromosomal abnormalities
mentioned above is approximately 85 percent with a false positive rate
of 5 percent. This means that:
- Approximately 85 out of every 100 babies affected by the abnormalities
addressed by the screen will be identified.
- Approximately 5 percent of all normal pregnancies will receive a positive
result or an abnormal level.
Drawn between 15 and 20 weeks of pregnancy, this test screens for chromosome
problems and open neural tube defects.
The quad screen test is a maternal blood screening test that looks for
four specific substances: AFP, hCG, Estriol and Inhibin-A.
- AFP: alpha-fetoprotein is a protein that is produced by the fetus
- hCG: human chorionic gonadotropin is a hormone produced within the placenta
- Estriol: estriol is an estrogen produced by both the fetus and the placenta
- Inhibin-A: inhibin-A is a protein produced by the placenta and ovaries
A positive result does not mean the baby has a problem, just that the baby
has an increased risk of a problem and warrants further investigation.
The integrated screen is a two-part blood test with the first part of the
test done with the NT test. It is a screening test for Down syndrome,
trisomy 18 and open neural tube defects.
A test is performed on the mother’s blood at 10 weeks and three days
to 13 weeks and five days to measure the levels of a protein normally
found in the blood of all pregnant women
- PAPP-A (pregnancy associated plasma protein-A)
A laboratory test performed on the mother’s blood at 15 to 18 weeks
to measure the levels of four proteins normally found in the blood of
all pregnant women
- AFP (Alpha fetoprotein)
- A laboratory test performed on the mother’s blood at 10 weeks and
three days to 13 weeks and five days hCG (Human chorionic gonadotropin)
- E3 (unconjugated estriol)
- Inhibin A
The Integrated Screen will detect up to 92 percent of babies affected with
Down Syndrome and up to 90 percent with Trisomy 18. It will also detect
up to 80 percent of babies who have open neural tube defects such as Spina
Bifida. Since the first and second trimester results are combined, your
risk assessment will not be available until your second trimester blood
work is completed.
An ultrasound exam is a procedure that uses high-frequency sound waves
to scan a woman's abdomen and pelvic cavity, creating a picture (sonogram)
of the baby and placenta. Ultrasounds are diagnostic procedures that detect
or aid in the detection of abnormalities and conditions related to pregnancy.
They may be ordered throughout your pregnancy for many different reasons.
Below is a list of the most common reasons ultrasound is ordered.
- Confirm viable pregnancy
- Confirm heartbeat
- Measure the crown-rump length or gestational age
- Assess abnormal gestation
- Nuchal Translucency
- Diagnose fetal malformation
- Weeks 13-14 for characteristics of potential Down syndrome
- Weeks 18-20 for congenital malformations
- Identify structural abnormalities
- Confirm multiples pregnancy
- Verify dates and growth
- Confirm intrauterine death
- Identify hydramnios or oligohydramnios – excessive or reduced levels
of amniotic fluid
- Evaluate fetal well-being
- Assess cervical length
- Identify placental location
- Confirm intrauterine death
- Observe fetal presentation
- Observe fetal movements
- Identify uterine and pelvic abnormalities of the mother
A detailed ultrasound is recommended in the second trimester to assess
fetal anatomy, placental position and maternal pelvic structure.