From the Guidelines
The most common cause of a cystic hygroma in the first trimester of pregnancy is chromosomal abnormalities, particularly Turner syndrome (45,X), which is associated with 50-80% of cases. Cystic hygromas are fluid-filled sacs that develop from malformations in the lymphatic system, typically appearing at the back of the fetal neck. When detected during first-trimester ultrasound, approximately 50-80% of cases are associated with chromosomal disorders, as noted in the study by SMFM 1. Besides Turner syndrome, other chromosomal abnormalities like trisomy 21 (Down syndrome), trisomy 18, and trisomy 13 can also cause cystic hygromas. The formation occurs due to failure of lymphatic vessels to connect properly with the venous system during embryonic development, leading to lymph fluid accumulation and subsequent cyst formation.
Some key points to consider in the diagnosis and management of cystic hygromas include:
- The importance of genetic counseling and additional testing such as amniocentesis or chorionic villus sampling to determine if a chromosomal abnormality is present, as this significantly impacts pregnancy management and outcomes 1.
- The need to evaluate for other potential causes of nonimmune hydrops fetalis, such as cardiovascular malformations, hematologic disorders, and infectious diseases, although chromosomal abnormalities are the most common cause in the first trimester.
- The prognosis for fetuses with cystic hygromas and associated chromosomal abnormalities can be poor, highlighting the importance of early diagnosis and management.
Overall, the identification of a cystic hygroma in the first trimester of pregnancy should prompt a thorough evaluation for chromosomal abnormalities and other potential causes of nonimmune hydrops fetalis, with management guided by the underlying etiology and prognosis.
From the Research
Cystic Hygroma in the First Trimester of Pregnancy
The most common cause of a cystic hygroma in the first trimester of pregnancy is associated with chromosomal abnormalities.
- Chromosomal abnormalities were found in 40.3% of the cases in one study 2
- The most common abnormality in nonseptated cystic hygroma was trisomy 21 (25%) and in septated cystic hygroma was Turner syndrome (21.1%) 2
- Trisomy 21 was also the most common abnormality in another study, found in 17 fetuses with cystic hygroma 3
- Other studies also reported aneuploidy, including trisomy 21, trisomy 18, and monosomy X, as common causes of cystic hygroma in the first trimester 4, 5
Associated Findings and Prognosis
Cystic hygroma is often associated with other structural malformations and a poor prognosis.
- Cardiac abnormalities were found in 20% of nonseptated cystic hygroma cases and nonimmune hydrops in 54.5% of septated cystic hygroma cases 2
- The overall survival rate was poor, with only 10.5% of cases alive 2
- Another study reported that only two fetuses with cystic hygroma were liveborn at term, both with an abnormal karyotype 5
- Hydrops fetalis was common in cases of cystic hygroma and was associated with a poor prognosis 5, 6
Diagnosis and Management
Prenatal diagnosis of cystic hygroma using ultrasonography and cytogenetic evaluation is crucial for determining the prognosis and management of the pregnancy.
- Transvaginal ultrasonography can be used to diagnose cystic hygroma in the first trimester 3, 4
- Karyotyping and a complete ultrasonographic search for associated anomalies are recommended for all cases of cystic hygroma 4
- Prenatal cytogenetic analysis should be offered to women with fetal cystic hygroma diagnosed in the first trimester 3