Pregnancy
IVF Babies
Prenatal monitoring and ultrasound scans
What is prenatal diagnosis?
Which test ?
Sex, IVF and Pregnancy
IVF Babies
In the 30 plus years after the first “test tube” baby about 5 million children have been born after ART in the world and due to the concerns and academic interest is a very well studied group.
Occasionally newspaper acticles give alarming claims that IVF children have a higher risk of this or that but this can be often traced to the fact that
-many pregnancies are multiple twins or even triplets (which always need special care and monitoring)
-in cases of severe male infertility the husbands may carry a higher risk of genetic abnormalities.
For example the father may be carry a mutation causing his infertility (but of course is as we would say in every respect normal) but the children could inherit this mutation.
-many small studies in the past have had flaws and cannot compare accurately children born.
For example IVF and ICSI mothers have a increased maternal age.
There are no adverse effects to the actual technique of ICSI-when a single sperm is injected into an oocyte and recent studies have allayed fears that there is a higher chance of affected children.
Prenatal monitoring and ultrasound scans
The amniocentesis and cvs are advised on the same basis as for naturally conceived pregnancies based on history and maternal age.
Ultrasound exams are usually carried out early on in the pregnant after ART about 6-7 weeks after the last period to confirm the ongoing pregnancy after the initial pregnancy blood test. After this the regularity of the scans are the same for all pregnancies.
2 weeks after positive test (Early ultrasound examination)
This is an ultrasound examination that is usually carried out vaginally. It aims to determine the number of fetus present and whether the pregnancy is progressing normally inside the uterus.
Second ultrasound Scan to determine "Clinical Pregnancy"
At 6-7 weeks the fetal heartbeat should be detected by vaginal ultrasound confirming a clinical pregnancy.
Further Scans
Ultrasound picture of a failed pregnancy at 10 weeks showing an empty sac (left) plus a viable pregnancy sac (right).
Nuchal translucency
Ultrasound picture of a 12-weeks fetus showing the normal nuchal translucency and nasal bone
Using the information from the scan and the following parameters a risk is calculated to determine the likelihood of your baby having a chromosomal abnormality.
• Age of the mother
• Amount of fluid behind the neck of the fetus (nuchal translucency)
• Presence or absence of the fetal nasal bone
• Presence or absence of any gross physical abnormalities
• Level of two hormones (ß•hCG & PAPP•A) in the mother’s blood (formally alpha test??)
• Previous history
When is it carried out?
11 – 14 weeks
What does it look for?
During the scan the amount of fluid at the back of your baby’s neck (Nuchal Translucency).
At this gestation the fetus will be 2 – 3 inches (5 – 8cms) long and the heartbeat can be demonstrated on the screen. The "crown-rump" length will be measured and your expected date of delivery confirmed.
After the scan, on the basis of all the above factors, the estimated risk for Downs Syndrome will be discussed with you.
What is prenatal diagnosis
Prenatal diagnosis is a way for your doctor to tell or suggest if your fetus has a problem.
Amniocentesis and chorionic villus sampling (CVS) are tests that help find genetic disorders before birth. Some parents are at increased risk of having a baby with a genetic disorder or other problem and may want to have one of these tests.
Before embarking on the test they have to concider the potential dilemma to discontinue the pregnancy if a problem is found. Knowing about problems before the baby is born may help parents make decisions about health care for their infant. Certain problems can be treated before the baby is born, while other problems may need special treatment right after delivery. In some cases, parents may decide not to continue the pregnancy.
CVS is usually performed between the 10th and 14th weeks of pregnancy.
Amniocentesis is usually performed after the 15th week of pregnancy or later.
Do all pregnant women have these tests?
No. Amniocentesis or CVS may be considered in situations in which the parents are at increased risk of having an infant with a genetic disorder. The tests may be useful if you are 35 years of age or older by the time your baby is due or at any time when the parents could not live with the possibility that there child will carry a genetic disorder.
The risk of having a baby with a chromosome abnormality, such as Down syndrome is increased with maternal age. The tests may also be useful if you have previously had a child with Down syndrome or another disorder, such as spina bifida.
The test may also be helpful if you or your partner are known carriers of a genetic disorder, such as cystic fibrosis or beta thalaseamia
CVS
-involves the examination of chorionic villi (placental tissue).
Both the baby and placenta originate from the same cell and so the chromosomes present in the cells of the placenta are the same as those of the baby.
Local anesthesia is used.
The sample is commonly obtained by inserting a needle into the abdomen and withdrawing some of the placenta. The needle is carefully observed using ultrasound scan. The procedure lasts 1-2 minutes.
Most women feel fine after the test, although some may have mild bleeding (spotting) afterward.
The results for Downs Syndrome and other major chromosomal defects are usually available 12 days.
Amniocentesis
During amniocentesis, a sample of amniotic fluid (the fluid around the baby) is removed from your uterus and sent to a laboratory for evaluation. Amniocentesis is performed by inserting a thin needle through your abdomen into your uterus and withdrawing a small amount of fluid. Your body will make more fluid to replace the fluid that is taken out. The baby will not be hurt during the procedure as this is done under ultrasound visualization. Some women feel mild cramping during or after the procedure. Your doctor may tell you to rest on the day of the test, but usually you can resume normal activity the next day.
risks.
The risk of miscarriage due to CVS is about 1% and this is the same as the risk from amniocentesis.
Your doctor will talk to you about the risks, benefits and if the benefits of knowing about a potential disorder are greater than the risks.
Which test ?
There are some situations in which amniocentesis is more appropriate than CVS. Amniocentesis is preferred if you have previously had a baby with a neural tube defect or if you or your partner have a neural tube defect. (CVS doesn't detect neural tube defects.)
Amniocentesis may be better if the results of other tests such as the alpha-fetoprotein test during your pregnancy have been abnormal. The blood screening test may show that your infant is at greater risk of having a neural tube defect or a disorder such as Down syndrome.
CVS may be better if you and your doctor want to know the test results during your first trimester.
20 weeks scan
Irrespective of whether or not you decide to have an invasive test, it is recommended that you have a scan at 20 weeks to check for physical abnormalities.
This scan can almost always be carried out transabdominally.
1) the size of the fetus is measured .
2. To assess the risks of Downs Syndrome and other chromosomal abnormalities.
3. To diagnose multiple pregnancy well being
Ultrasound scanning can determine if both babies are developing normally and if the babies share the same placenta which can lead to problems in the pregnancy. In such cases it would be advisable to monitor the pregnancy more closely.
4. To diagnose certain major fetal abnormalities
5. To diagnose early pregnancy failure
Fetal cardiac scan ~ 20 weeks
A detailed examination of the fetal heart and connecting vessels is carried out. It is especially recommended for women with a family history of heart abnormalities, or where increased nuchal translucency had been found at the 12 week scan. It is also an important scan in assessing the risk for Downs Syndrome because many of these babies have heart abnormalities.
Fetal wellbeing scan 24+ weeks
Most obstetricians advise that an ultrasound scan to assess fetal growth and wellbeing is offered to all women at about 30-32 weeks of pregnancy..
This scan aims to determine the growth and health of the fetus by:
• Measurement of the size of the fetal head, abdomen and thigh bone and calculation of an estimate of fetal weight
• Evaluation of the placental position and appearance
• Measurement of the amount of amniotic fluid
• Examination of the movements of the fetus
• Blood flow to the placenta and fetus by colour is assessed using Doppler ultrasound.
