Case Report Suggests Signs of PWS During Pregnancy

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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During pregnancy, Prader-Willi syndrome (PWS) may manifest as an excess of fluid around the developing fetus coupled with restricted fetal growth and decreased fetal movement, a new report indicates.

These signs should alert clinicians to consider testing for the possibility of a PWS diagnosis, the researchers wrote.

The report, “Cardiac rhabdomyoma as a possible new prenatal sonographic feature of Prader–Willi syndrome,” was published in the Journal of Obstetrics and Gynaecology Research.

Scientists in Thailand described the case of a 40-year-old woman referred to their center. This was the woman’s third pregnancy. The first was normal, with delivery by cesarean section, due to non-reassuring fetal heart rate. The second ended in an elective abortion after the fetus was found to have trisomy 21 (also known as Down syndrome).

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Because of the advanced maternal age and the prior history of genetic defects, she underwent genetic amniocentesis, a test that looks for large genetic abnormalities in the developing fetus. Results were normal, and the pregnancy appeared to be progressing uneventfully for the first several months.

At the 28th week of pregnancy, a routine ultrasound revealed polyhydramnios — an abnormally large amount of fluid around the developing fetus.

Another ultrasound screening three weeks later again showed polyhydramnios. Although the fetus had normally-shaped extremities, it was abnormally small (estimated weight in the 10th percentile), and no fetal movement was observed over an hour-long observation.

In addition, the imaging revealed a small rhabdomyoma — a rare type of tumor — on the unborn baby’s heart.

The woman and her partner underwent counseling to discuss these findings. Ultimately, because the fetus had no obvious deformities and the pregnancy was fairly advanced, they decided to wait until after the baby was born to do further genetic testing.

Through the rest of her pregnancy, the woman underwent regular tests to check for potential problems. Apart from a continued lack of fetal movement, the pregnancy was normal, and at 38 weeks, the baby was born via elective cesarean section.

The woman gave birth to a boy weighing 2,420 grams (5.3 pounds), putting him in the 8th percentile. Several abnormalities were noted, including hypotonia (low muscle tone), a thin upper lip, and under-developed genitals.

“The newborn survived, although [he] had several clinical problems, especially difficult feeding,” the researchers reported.

The combination of signs and symptoms before and after birth led the baby’s care team to suspect PWS, so genetic testing was ordered. Results were positive for PWS, confirming the diagnosis. Even though the baby had low muscle tone and showed weak sucking, breastfeeding was successful with special care by the mother.

Mental and physical impairments were not evident at two months. Growth was somewhat delayed, but was within the normal range. Still, the baby was scheduled for close follow-up.

The researchers concluded that “prenatal sonographic features of polyhydramnios, decreased fetal movement, and fetal growth restriction should alert physicians to list PWS” as a possible diagnosis.

The team also noted that, since both PWS and rhabdomyoma are extremely rare individually, finding both of them in the same patient indicates a potential connection.

Though they acknowledged this “could be a coincidental finding,” the team said it would be worthwhile to document whether the two conditions tend to co-occur, as rhabdomyoma may be “a possible new prenatal sonographic marker of PWS.”