Role of Ultrasound in Pregnancy
“Why the doctor is taking so much time for each patient scan? Either he is so free or inexperienced! Why can’t they just write the report?” She was sitting in a waiting room of an ultrasound clinic; it was very boring and tiring for her after a long workday. “My two kids are waiting at home, finally I’ll get date for Caesarian operation, Thanks to my general-practioner, but what will I answer if the radiologist asks me about not getting early third and fifth month scans? This pregnancy was very difficult as I had poor blood sugar control, off and on high blood pressure, baby movements were also sluggish for a week. Oh I was so busy with job and family that I couldn’t come for checkups, Thank God now this would be over”. Finally, after half an hour, she was called in ultrasound room and scan started She was looking at doctor’s face, smile vanished, rather, he seemed worried he stated asking questions after a detailed scan report was written. It was an intra uterine death with excessive water in brain, defective spine and heart abnormalities. The doctor said “if you would have come earlier on time this could be diagnosed and we could have picked early danger signs on ultrasound”. Now nothing could be done.
In another hospital, a mother was smiling to see her active normal newborn twin babies. All labour room staff members were also happy, as they timely delivered intrauterine growth retarted babies picked on ultrasound. On the next bed a post Caesarian delivery patient was feeding her baby, whose fetal distress and cord around neck were picked by fetal ultrasound.
These are few examples of significance of routine ultrasound scan during pregnancy. It is a non-invasive, affordable easily available test that gives most of the information of a baby before it is born. It is very crucial to have some basic information about it.
What is ultrasound?
These are simple, harmless sound waves that cannot be picked by human ears. These sound waves when bounce back from a structure, are picked by a probe and image is seen
When to have ultrasound?
When you miss your periods or not sure of dates and want to confirm exact duration, site, viability, number of pregnancy sacs get a pelvic ultrasound.
How frequent scan should be done in pregnancy?
Pregnant women should have at least one scan from 11 to 24 week i.e. third to fifth month of pregnancy, extra scans are required if there are certain problems like medical disorders like high blood pressure, diabetes, cardiac problems, or growth retardation problems of baby. These scans should be done if advised by a doctor for a particular reason.
How it is done?
You have to take an appointment before coming. You would be asked to come with a full bladder for an abdominal scan. You will be asked to lie on a couch, after applying gel on tummy, scan probe is put, which gives images on the screen. Sometime in early pregnancy vaginal ultrasound is done with empty bladder, and the doctor will discuss about it.
What is checked in at 11 to 13 week scan?
Pregnancy dating, number of babies growing and detailed examination for major structural abnormalities is done .It can save you and your baby for future problems.
How can we pick Down syndrome as early as possible?
At around 13 weeks the fluid in the skin behind the neck of baby is measured, if it is more than 4mm then it is combined with maternal blood test of serum estriol levels. Invasive tests like amniocentesis and chorioni villous sampling can also be done.
What are risk factors for Down syndrome?
Maternal ages more than 40 years, family history, a previous sibling with Downs are predisposing factors.
What is ultrasound guided invasive tests for before delivery diagnosis of genetic disorders?
Amniocentesis is needle-guided aspiration of fluid around baby, done around 13 weeks. Chorionic villous sampling is needle biopsy of placenta. Both these tests give genetic make up of baby and pick chromosomal anomalies at a very early stage.
When should these tests be done?
If your doctor is suspecting any problem, you have a history of abortions; age more than 40 years, family history of cystic fibrosis, thalassemia, conge tally malformed babies and structural defects. These tests can save you from a lot of future problems.
What happens at 20 to 24 week scan?
At this stage baby has grown big enough to be examined in more detail. The defects of heart, brain and backbone, limbs, eyes and abdominal wall can be seen .If your baby is normal at this scan then there are less chances of having a problem afterwards. But 8 to 10 % of congenital defects can be missed on ultrasound
What if a problem is identified at 20 to 24 week scan?
Most problems need a repeat follow-up scan after 2 to 3 weeks .If there is some suspicions on scan then some invasive maternal and fetal tests could be done. These are mother blood samples for viral infections, hormone profile, blood sugar levels and these are correlated with lab values of amniocentesis (test of fluid around fetus) or chorionic villous sampling (CVS).
What congenital abnormalities could be identified on ultrasound?
The structural defects of brain and spinal cord can be identified easily whereas it is not possible to pick eye, ear defects and brain function disorders like cerebral palsy.
Here are certain problems and there chances of being picked:
- Absence of head (anencephaly) 99%
- Open spinal cord (spinal bifida) 90%
- Limb defects (missing bones or very short limb) 90%
- Absent abdominal wall (examphalos) 90%
- Down syndrome (learning and physical problem) 85%
What is checked in a routine obstetrical ultrasound in mid trimester?
In this scan measurements of fetal body like head, thigh-bone (femur) length, and abdominal circumference are checked for that age and growth is estimated. Liquor (fluid around baby) amount tells about fetal renal function and it is first to be reduced in cases of fetal growth retardation. Similarly its site upper or lower uterine segment decides mode of delivery. Doppler blood flow tells about blood flow in umbilical vessels going to fetus. In twin pregnancy this blood flow checking picks problems of twin-to-twin transfusion.
What is biophysical profile?
This is ultrasound-guided observation of a fetus for 20 minutes. Fetal heart rate, body tone and movements, amount of water around baby is measured. It is correlated with overall health status of baby.
How important is last trimester ultrasound?
Fetal biometry, head, thigh bone length, tummy size, placental localization, amount of liquor, all decide mode of delivery and fetal outcome.
The simple ultrasound test is so helpful in modern obstetrics that it is not only helping in picking problems at a very early stage but also improving survival of new born. You should know it is true that, “NO ONSTETRICAL EXAMINATION IS COMPLETE WITHOUT AN ULTRASOUND”
Dr. Ayesha Azam Khan