Ultrasonography is an integral part of pregnancy evaluation these days. Right from determining whether a pregnancy exists in the first place, to monitoring the progress of the fetus and looking for fetal and maternal complications, ultrasound is an invaluable tool. Obstetrics is the killer app for ultrasound and so useful is it that it is better to overuse the modality than to regret not having used it earlier. It is cheap and portable and completely safe for the mother and the baby, unlike x-rays, which are known to be harmful.

Ultrasound uses high-frequency sound waves in the frequency range of 1-5Mhz, as compared to our normal audible range, which is between 20 and 20000Hz. An inverted "T-shaped" transducer that converts electrical energy to sound waves is placed on the abdomen of the mother and moved back and forth, while the sound waves emitted enter the abdomen. Depending on the tissues and organs that they encounter, these sound waves are partly reflected back to the transducer and partly transmitted further on in the body, the reflected waves giving us a grey-scale depiction of the tissues within the body.

Ultrasonologists are usually radiologists who have gained special expertise and training in this field. Unlike other areas of radiology, ultrasound is completely operator-dependent and therefore a good ultrasonologist is a great asset. Gynecologists often perform their own ultrasound, and though this may be acceptable for basic evaluation, when anything more complicated or specialized needs to be done, the patients should be referred to radiologists.
 

High-Risk Pregnancies and Ultrasound

In a typical pregnancy, ultrasound may be performed twice or thrice. In high-risk pregnancies the frequency may go up to once every month, which is what happened with us.

Between the 16th-23rd weeks, the sonologist usually concentrates on looking for congenital fetal anomalies. This involves detailed scanning of the fetal brain, skull, heart, lungs, abdominal organs, urinary system, spine and limbs and the scan may take anywhere from 15-45 minutes. If an anomaly is picked up, its significance has to be ascertained and then the parents are counseled accordingly.

Luckily there was no problem with either of the babies, though one was always a little smaller than the either. By measuring the head circumference and the abdominal circumference on the ultrasound, we knew what their weight was and these parameters were then matched with the expected date of delivery calculated on the basis of the days elapsed since the last menstrual period, to ascertain growth mismatch. The absence of a growth mismatch was a relief since with twins, intra-uterine growth retardation is a little more common.
 

Sex and the Fetuses

By the time the 26th week came, our parents started asking us about the sex of the babies. We told them that it was not necessary to know the sex and it would be nice to be a little surprised during delivery, but grandparents being grandparents, they would needle us once every now and then. And truth be told, I too didn't mind knowing in advance. 

Our ultrasonologist is a fervent member of the "sex not to be told" brigade. Many gynecologists and ultrasonologists have this attitude, because of the problems related to the issue of sex discrimination. Many people indiscriminately abort female fetuses at advanced ages, even when abortion is harmful for the mother and to avoid these problems many doctors have a blanket rule of never revealing the sex of the fetus to the parents. And they make no exceptions so that they can avoid potential moral dilemmas. There are others who however take a different stand and reveal the sex to the parents if asked to, on the grounds that what the parents do with this information is none of their concern and mentioning the sex is a routine part of the ultrasound report. I think that depending on the patient, an informed judgement call can be made and doctors really don't have the right to play God.

Knowing a bit of fetal ultrasound anatomy, each time the transducer would pass over the pelvic regions of the fetuses, I would peer at the images trying to look for the tell-tale "penis" appearance. Typically the penis appears an elongated tubular structure between the thighs. The absence of such a structure suggests a female. Knowing that I was looking, the sonologist would try not to linger in the pelvic region and I was never really sure. Though I knew one thing; at least one of them was a girl.

Which meant we would either have two girls or one girl and one boy.

We started thinking of baby names, keeping both possibilities in mind.

If you would like to share your thoughts on this article or view other people's comments, Click Here.

If you would like to correspond directly with the Man From Matunga, send him an email at me@manfrommatunga.com

For more of his articles, visit www.manfrommatunga.com