Umbilical Cord Diameter at Early Second Trimester: Relation to Trisomy 21

Area of Science:

• Prenatal diagnosis
• Fetal medicine
• Genetics

Background:

• Trisomy 21, also known as Down syndrome, is a genetic disorder.
• Early second-trimester ultrasound measurements may offer insights into fetal well-being.
• Umbilical cord diameter (UCD) is a potential biometric parameter.

Purpose of the Study:

• To compare UCD in fetuses with trisomy 21 versus normal fetuses at 17-19 weeks of gestation.
• To evaluate the utility of UCD measurement for screening trisomy 21.

Main Methods:

• A case-control study involving 39 fetuses with trisomy 21 and 39 controls.
• UCD was measured between 17-19 weeks of gestation.
• Trisomy 21 was confirmed by chorionic villus sampling or amniocentesis; controls were low-risk and confirmed euploid postnatally.

Main Results:

• Mean UCD was slightly lower in trisomy 21 fetuses (7.48 ± 0.99 mm) compared to controls (7.66 ± 0.91 mm), but this difference was not statistically significant (P = 0.41).
• No significant differences in UCD were observed based on maternal variables like BMI or obstetric history.
• Mothers with a prior cesarean section showed a significantly lower mean UCD (7.21 ± 0.97 mm) compared to those without (7.71 ± 0.97 mm; P = 0.03).

Conclusions:

• While fetuses with trisomy 21 may have a thinner UCD at 17-19 weeks, the difference is not significant enough for clinical screening.
• UCD measurement alone is not a reliable screening marker for trisomy 21 in early second trimester.