Determining the gender of twins can be an exciting yet complex process, especially during pregnancy. The Non-Invasive Prenatal Test (NIPT) has become a reliable option for expecting parents seeking early and accurate gender information. But how accurate is the NIPT test for twins?
This advanced prenatal screening not only detects chromosomal conditions but can also predict the gender of your twins with impressive precision. In this article, we explain the accuracy of the NIPT test for twins, how it works, and factors that may influence results, providing you with everything you need to know to make informed decisions about prenatal testing.
What Is NIPT and How Does It Work?
Non-invasive prenatal testing (NIPT) analyses cell-free DNA from a pregnant woman's maternal blood. This test screens for chromosomal abnormalities such as fetal trisomies (e.g., Down syndrome) and provides fetal gender determination. By examining fragments of DNA shed from the placenta into the mother’s bloodstream, health professionals can detect chromosomal disorders without requiring invasive procedures like chorionic villus sampling or amniocentesis.
How NIPT Works
How Accurate is NIPT in Determining Twin Gender?
Gender Accuracy for Identical Twins
Non-invasive prenatal testing (NIPT) is highly accurate for determining gender in identical (monozygotic) twins. Identical twins originate from a single fertilized egg that splits, resulting in two individuals with identical genetic material. This shared genetic composition simplifies the detection of sex chromosomes, as both fetuses will exhibit the same sex chromosome pattern. Studies confirm that NIPT accurately determines the gender of identical twins with nearly 100% reliability (Norwitz et al., 2019).
Gender Accuracy for Fraternal Twins
For fraternal (dizygotic) twins, determining gender with NIPT presents challenges due to the independent genetic contributions from two fertilized eggs. The accuracy of NIPT in detecting gender depends on the ability to distinguish DNA fragments originating from each fetus.
- Differing DNA Contributions: Since fraternal twins do not share identical DNA, the fetal fraction of each twin's DNA in the mother's blood can vary, making it more difficult to attribute specific chromosomal markers to each fetus accurately (Picchiassi et al., 2012).
- Potential Errors: Misattribution of DNA fragments can lead to errors in gender determination. If the DNA of one fetus dominates the sample, it might obscure the signal of the second fetus. Additionally, cases like vanishing twins can leave residual DNA in the mother's blood, further complicating the analysis and potentially leading to false results (Curnow et al., 2015).
- Ambiguities: In some cases, NIPT may only confirm the presence of a Y chromosome without specifying whether it belongs to one or both fetuses, leading to uncertainty in gender prediction (Grömminger et al., 2014).
Fetal Gender Determination in Twins: Possible Challenges
Determining fetal gender in twin pregnancies using non-invasive prenatal testing (NIPT) can be highly accurate, but it comes with unique challenges. Factors like vanishing twin syndrome, shared placentas, and fetal DNA fractions can affect results, making it essential to carefully interpret NIPT findings in twin pregnancies:
- Fetal Fraction Correlation: The percentage of cell-free fetal DNA fraction in the maternal bloodstream must meet a specific threshold to ensure reliable results. Fetal fraction estimation can vary depending on maternal weight, gestational age, and maternal risk factors (Majid Zaki-Dizaji et al., 2023).
- Placental Mosaicism: Instances of placental mosaicism, where abnormal cells are present in the placenta but not in the fetus, may affect gender determination and lead to false-positive results or false-negative results (Anne Mardy et al., 2016).
- Monochorionic Monoamniotic Twins: In rare cases of monochorionic monoamniotic twins, NIPT cannot differentiate fetal DNA contributions, increasing the likelihood of gender assignment error (Darine Villela et al., 2019).
- Vanishing Twin Syndrome: Vanishing twin syndrome occurs when one fetus is lost early in pregnancy. Residual cfDNA from the demised twin can lead to false-positive or false-negative results for chromosomal abnormalities and gender assignment errors (Jacintha C A van Eekhout et al., 2023).
NIPT in Twin Pregnancies vs. Singleton Pregnancies
NIPT (Non-Invasive Prenatal Testing) is widely used in both singleton and twin pregnancies, but its accuracy and complexity differ between the two. In singleton pregnancies, the test analyzes cell-free DNA (cfDNA) from the fetus present in the mother’s bloodstream, achieving high accuracy in detecting chromosomal abnormalities like Down syndrome (trisomy 21) and determining the baby’s gender. The straightforward nature of analyzing DNA from a single fetus makes NIPT in singleton pregnancies highly reliable, with detection rates often exceeding 99%.
In twin pregnancies, however, the process becomes more complex. NIPT must analyze cfDNA contributions from both fetuses, which are mixed together in the mother’s blood. Advanced algorithms are required to differentiate between the two DNA sources, especially when screening for chromosomal abnormalities or determining fetal sex. Challenges arise in cases of monochorionic twins (twins sharing a placenta) or when the fetal DNA fraction is low.
Is an NIPT Test More Accurate than an Ultrasound?
An NIPT test is generally more accurate than an ultrasound for gender assignment accuracy and detecting genetic disorders. While ultrasounds can estimate fetal gender around 18-20 weeks, NIPT offers a non-invasive, highly precise accurate sex prediction model using maternal blood to analyze cell-free DNA as early as 10 weeks into the pregnancy. This method detects chromosomal abnormalities and can identify conditions like sex chromosome aneuploidies much earlier.
Whilst, NIPT is essentially a definitive diagnosis; in some cases, additional testing like chorionic villus sampling (CVS) or amniocentesis may be recommended for a conclusive result. Healthcare providers rely on both methods for comprehensive prenatal care and chromosome detection.
When Can You Get an NIPT Test?
You can get an NIPT test as early as 10 weeks into pregnancy, making it an excellent option for expectant parents who want early insights into fetal health. EarlyReveal’s NIPT test is a leading option, offering 99.9% accurate chromosome detection and fetal sex determination from a simple blood sample.
Take Advantage of EarlyReveal’s Fetal Gender Identification Tests
At EarlyReveal, we offer two convenient options for early fetal gender determination. Our at-home blood test and clinical blood test, both available as early as 7 weeks, provide accurate results for gender identification from a simple blood sample.
For those seeking a more comprehensive screening, our NIPT Trisomy test, available at 10 weeks, screens for common chromosomal abnormalities like Down syndrome while also confirming fetal gender. Whether you prefer the convenience of home testing or the thoroughness of a clinical setting, we provide reliable, early results to help guide your pregnancy decisions!
