Do you know of these 4 rare prenatal conditions?

Acardiac twins develop when one embryo splits into two, however, they only have one functional heart. One developing baby, called the “pump twin”/normal twin is endowed with the heart, while the other, called the “acardiac twin”/abnormal twin lacks a heart.

Acardiac twins are monochorionic, that is, the babies have two separate umbilical cords but share the same placenta. However, there exists an anastomosis in the umbilical cord of the two babies. This means that instead of being completely separate, they are joined to one another. Broadly, these can be artery-to-artery or vein-to-vein. This condition occurs in 1 percent of all monochorionic pregnancies.

Wastes from the normal twin enters the abnormal twin due to the connection present between them. This phenomenon is commonly called twin reversed arterial perfusion (TRAP) sequence or acardial twinning. Due to this, the abnormal twin becomes a deformed mass of tissue that commonly only has a lower body and limbs. The abnormal twin is often called the parasite twin since it receives its oxygen from the normal baby. Increased pumping of the normal baby’s heart may cause a cardiac failure.

The survival of the normal twin depends on the relative size of both foetuses. The mortality of the abnormal twin is 100 percent.

2. Twin Anaemia Polycythemia Sequence (TAPS)

Similar to acardiac twins, twin anaemia polycythemia sequence (TAPS) is a type of twin-to-twin transfusion syndrome that occurs in monochorionic twin pregnancies. About 3-5 percent of all such pregnancies may lead to TAPS. They also exhibit anastomosis that are smaller in diameter, and connecting artery-to-vein, that is, both have their independent hearts but one pumps blood into the other.

In TAPS, there is uneven circulation of blood count among the two babies. One baby gets an excess supply of red blood cells and haemoglobin, causing polycythemia whereas the other baby gets an inadequate supply, making them anaemic. The polycythemic baby is called the “recipient twin” and the anaemic baby is the “donor twin”, and the donor pumps blood into the recipient.

Since the recipient twin gets more blood, there exists a risk of slow blood flow, hence leading to excessive strain on the heart and blood clot formation or thrombosis. The donor twin might be underdeveloped as it does not receive the adequate amount of oxygen and nutrients it requires for its growth.

TAPS may occur by chance or due to the laser treatment of TTTS.

3. Congenital Diaphragmatic Hernia (CDH)

The diaphragm in the human body is a thin muscle that exists on the base of the lungs, separating the chest and the rest of the abdomen. In congenital diaphragmatic hernia (CDH), a defect in the diaphragm of the growing baby causes the formation of a hole. This indicates that the contents of the chest and the abdomen are not properly separated. Thus, certain abdominal organs like the stomach, parts of the intestine, and liver move into the chest cavity. These crowd into the space available for the lungs, affecting their normal development.

Such babies suffer from pulmonary hypoplasia impacting oxygen levels and how well they are able to breathe. The estimated incidence of this condition has been reported to be between 1 or 5 children in 10,000 births. CDH may occur due to anomalies in the baby’s chromosomes, but most cases do not have a genetic cause (called isolated CDH). It becomes imperative to perform a genetic diagnosis.

4. Foetal Hydrothorax

The organs of the chest (lungs, heart) have spaces between them. In a foetus, when fluid collects in this space it is referred to as foetal hydrothorax. Accumulation of fluid in the limited space of the chest can result in displacement of the heart and compression of the lungs.

Similar to the conditions mentioned above, foetal hydrothorax can lead to pulmonary hypoplasia (as the lungs are compressed) and may also lead to heart failure.

The incidence of this complication has been reported to be about 1 in 10,000 or 1 in 15,000 pregnancies. Foetal hydrothorax can occur due to genetic defects, infections or underlying conditions in the heart or lungs.

Detection and remedy

A number of rare prenatal complications can take place due to a late age of conception which hampers the genetic makeup of the eggs. It is imperative that pregnancies should be monitored thoroughly to spot any complications. One of the most common ways to do this is through routine ultrasonography. Upon finding an anomaly, further detailed tests and advanced imaging techniques can be utilised by specialists.

These complications may be addressed while the babies are still inside the womb. Such timely interventions are necessary to help save their lives and to avoid too much damage. Acardiac twins and TAPS can be treated with the help of intrauterine foetal therapy using lasers. Damage done by CDH can be reverted to a great extent with the help of foetoscopic tracheal occlusion (FETO); they may also undergo post-delivery surgeries. Procedures to drain the fluid can be used in foetal hydrothorax using foetal thoracentesis and thoracoamniotic shunting.

Although these complications represent exceptional cases, medical advancements have ensured that these pregnancies and precious lives are saved, and in time.

(The writer is CEO & Co-Founder, Indira IVF.)