A 31-year-old pregnant woman underwent NIPT testing and ultrasounds during the first 6 months of her pregnancy at Tam Anh General Hospital, District 7, with no abnormalities detected. At 28 weeks, the fetus developed polyhydramnios and moderate hydronephrosis due to ureteropelvic junction obstruction.

Doctor Nguyen Phuong Thao of the Fetal Medicine Unit conducted genetic testing, diagnosing the fetus with an HNF1B gene mutation. This mutation, located on chromosome 17, affects the function of several organs, including the liver, kidneys, pancreas, urinary tract, and reproductive system. It is a dominant mutation, meaning only one mutated copy of the HNF1B gene is sufficient to cause the condition. In this case, as neither parent showed symptoms related to the HNF1B gene mutation, it is highly likely that the fetus developed a new, spontaneous mutation during conception, according to Doctor Thao.

The pregnant woman underwent close ultrasound monitoring to assess the progression of hydronephrosis and amniotic fluid levels. Doctors also examined other organs, including the digestive system, heart, and reproductive organs, to detect any associated abnormalities. After birth, the baby will require urine tests and kidney ultrasounds to evaluate kidney function and the severity of the ureteropelvic junction obstruction, which will inform the surgical plan at the appropriate time. The baby also has a high risk of developing diabetes due to potential pancreatic beta-cell dysfunction and reduced insulin production. Therefore, the baby's blood sugar levels will be monitored after birth to develop a personalized treatment plan combined with a suitable diet to prevent early onset of the disease and its complications.

Doctor Thao advises the couple to undergo genetic testing before their next pregnancy to determine if they carry the HNF1B gene mutation. If neither parent carries the mutation, the risk of recurrence in subsequent pregnancies is generally low.

Doctor Thao provides genetic counseling to a couple at Tam Anh General Hospital, District 7. Photo illustration: Ngoc Chau

Doctor Thao provides genetic counseling to a couple at Tam Anh General Hospital, District 7. Photo illustration: Ngoc Chau

Urinary tract dilation is a common abnormality detected during prenatal ultrasounds. This condition encompasses congenital malformations of the kidneys and urinary tract, ranging from mild, self-resolving cases to severe cases requiring surgery. Affected areas within the urinary system can include ureteropelvic junction obstruction, ureterovesical junction obstruction, vesicoureteral reflux, duplicated collecting system, posterior urethral valves, urethral stenosis or atresia, and prune belly syndrome.

"Establishing the link between urinary tract dilation and genetic abnormalities is crucial for prenatal counseling, long-term management, and prognosis," Doctor Thao said, citing research indicating that chromosomal abnormalities are found in 12-24% of urinary tract dilation cases through genetic testing. Chromosomal abnormalities associated with urinary tract dilation include Down syndrome, Turner syndrome, DiGeorge syndrome, Wolf-Hirschhorn syndrome, 18q and 17q12 deletions, and HNF1B and PKD gene mutations.

Doctor Thao recommends regular prenatal checkups, especially at 4 key ultrasound milestones: 11-13 weeks and 6 days, 18-22 weeks, 28-32 weeks, and 36 weeks. The third-trimester morphology ultrasound (from 28 weeks onwards) can detect approximately 15-30% of new or previously undetected abnormalities compared to the second-trimester scan. During this stage, doctors can assess fetal growth, placental position, amniotic fluid levels, and late-onset abnormalities such as kidney, genitourinary, congenital heart, and central nervous system issues for optimal pre- and postnatal care for both mother and baby.

Ngoc Chau