Amniocentesis for Twin Pregnancies: Is Alpha-Fetoprotein Useful in Confirming that the Two Sacs Were Sampled?

University of British Columbia - Vancouver, Vancouver, British Columbia, Canada
Fetal Diagnosis and Therapy (Impact Factor: 2.94). 02/2007; 22(3):221-5. DOI: 10.1159/000098722
Source: PubMed


To assess if amniotic fluid alpha-fetoprotein (AFAFP) could be useful to determine if both sacs are sampled during an amniocentesis for twin pregnancies.
We reviewed all amniocenteses performed on twin pregnancies over a 5-year period. Inclusion criteria were restricted to pregnancies where both karyotypes and AFAFP were available on each fetus. Pregnancies complicated by fetal anomalies were excluded. The following information was obtained: maternal age, gestational age at the procedure, karyotypes, AFAFP values, pregnancy and neonatal outcome. Placental pathology reports were used to confirm chorionicity. Analysis was performed to evaluate the impact of the fetal gender and chorionicity on the AFAFP values.
260 pregnancies were reviewed. Mean maternal age was 36.9 years (33.6, 40.1). Gestational age at the time of the procedure was 16.2 weeks (14.5, 17.9). Complications included 1.8% of misdiagnosis (discrepancy between karyotype and gender). The difference of AFAFP values between the two fetuses was statistically larger in dichorionic pregnancies than in monochorionic gestations. Fetal gender had no influence on the AFAFP.
Amniocentesis in twin pregnancies is associated with a 1.8% risk of misdiagnosis. AFAFP can help to assess the chorionicity of a twin pregnancy. When the difference between the two values is <0.2 MoM and the chorionicity was thought to be dichorionic and the two karyotypes are similar, then failure to sample both sacs should be suspected.

6 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Over the past few years, the rising rate of multiple pregnancies, attributed to both increasing reliance on infertility treatment modalities and delayed childbearing, has expanded the need for prenatal invasive genetic testing. In multiples, first-trimester chorionic villus sampling and second-trimester amniocentesis are relatively safe and efficient alternative procedures, whereas fetal blood sampling is reserved for cases where an indefinite result of fetal karyotyping needs elucidation. The choice of invasive technique should be based on gestational age at referral date, procedure related risks and technical demands, but experience of the center performing the modality should be emphasized in decision making. Technological advances in modern high resolution ultrasound equipment along with increasing operator experience available today result in more accurate and efficacious invasive prenatal diagnosis in twin or higher-order pregnancies, minimizing potential post-procedural fetal loss rate.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective was to determine the risk of sampling error in amniocentesis and chorionic villus sampling (CVS) in singleton and multiple pregnancies. Data from this and other published studies were used to discuss current practice guidelines for molecular identity testing. Clinical and laboratory records of all patients undergoing molecular-based identity testing in our clinical laboratory from July 2002 until March 2008 were reviewed. DNA microsatellite testing was performed to determine zygosity in multiple pregnancies and maternal cell contamination (MCC) in both singleton and multiple pregnancies. MCC was detected in 6/148 (4%) CVS and 1/87 (1%) amniotic fluids from singleton pregnancies. In two of the CVS, only maternal cells were found. In 2/24 (8%) twin pregnancies, the same fetus was tested twice. In a total of 285 pregnancies (235 singleton, 24 twin, 26 with >or= 3 fetuses), without molecular identity testing, four women would have received erroneous results. Current guidelines recommend molecular identity testing for MCC in conjunction with molecular diagnostic testing, but not for cytogenetic testing. No published guidelines were found for zygosity testing in multiple pregnancies. We suggest that identity testing be considered for all prenatal testing of multiple pregnancies, especially if CVS is performed.
    Prenatal Diagnosis 08/2010; 30(8):746-52. DOI:10.1002/pd.2530 · 3.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The rate of twin pregnancies in the United States has stabilized at 32 per 1000 births in 2006. Aside from determining chorionicity, first-trimester screening and second-trimester ultrasound scanning should ascertain whether there are structural or chromosomal abnormalities. Compared with singleton births, genetic amniocentesis-related loss at <24 weeks of gestation for twin births is higher (0.9% vs 2.9%, respectively). Selective termination for an anomalous fetus is an option, although the pregnancy loss rate is 7% at experienced centers. For singleton and twin births for African American and white women, approximately 50% of preterm births are indicated; approximately one-third of these births are spontaneous, and 10% of the births occur after preterm premature rupture of membranes. From 1989-2000, the rate of preterm twin births increased, for African American and white women alike, although the perinatal mortality rate has actually decreased. As with singleton births, tocolytics should be used judiciously and only for a limited time (<48 hours) in twin births. Administration of antenatal corticosteroids is an evidence-based recommendation.
    American journal of obstetrics and gynecology 10/2010; 203(4):305-15. DOI:10.1016/j.ajog.2010.04.031 · 4.70 Impact Factor
Show more