Julia Zachary

A Randomized Comparison of Transcervical and Transabdominal Chorionic-Villus Sampling

BACKGROUND Chorionic-villus sampling is done in early pregnancy to obtain fetal cells for the prenatal diagnosis of genetic and chromosomal defects. Transcervical chorionic-villus sampling has been shown to be safe and effective in national trials. Recently, an alternative transabdominal technique has been suggested as potentially easier and safer. METHODS From April 1987 through September 1989, we prospectively compared transcervical and transabdominal chorionic-villus sampling in 3999 women with singleton pregnancies in whom the risk of a genetically abnormal fetus was increased. Women between 7 and 12 weeks of gestation underwent ultrasonographic evaluation of placental and uterine position. Those with active vaginal infections, active bleeding, or cervical polyps were excluded. If the obstetrician thought either sampling procedure was acceptable, the woman was asked to consent to random assignment to one of the two procedures. Both groups were followed to determine the outcome of pregnancy and the rate of spontaneous fetal loss after chorionic-villus sampling. RESULTS Among the 3999 women who entered the study, sampling was attempted in 3873 (97 percent), 1944 of whom had been assigned to undergo transcervical sampling and 1929 to undergo transabdominal sampling. Of these 3873 women, sampling was eventually successful in 3863. Sampling was successful after a single insertion of the sampling instrument in 94 percent of the transabdominal procedures and 90 percent of the transcervical procedures. Among the women with cytogenetically normal pregnancies who had sampling because of maternal age, the rate of spontaneous fetal loss through 28 weeks of pregnancy was 2.5 percent in the transcervical-sampling group and 2.3 percent in the transabdominal-sampling group (difference, 0.26 percent; 95 percent confidence interval, -0.5 to 1.0 percent). CONCLUSIONS Transabdominal and transcervical chorionic-villus sampling appear to be equally safe procedures for first-trimester diagnosis of fetal abnormalities.

Randomised comparison of amniocentesis and transabdominal and transcervical chorionic villus sampling

We have compared three methods of prenatal diagnosis in two large obstetric centres in Denmark. Women were randomly assigned transabdominal (TA) chorionic villus sampling (CVS), transcervical (TC) CVS, or second-trimester amniocentesis (AC); women at high genetic risk were randomised between the two CVS groups only. Analysis of 45 epidemiological variables showed the three procedure groups to be similar at enrollment. All women were followed up until completion of pregnancy. Among 3079 women at low genetic risk total fetal loss rates were 10.9% for TC CVS, 6.3% for TA CVS, and 6.4% for AC (p < 0.001). More women had bleeding after the procedure in the CVS groups (p < 0.001), whereas more amniotic fluid leakage (p < 0.001) was reported after AC. No uterine infections occurred in any group. No case of oromandibular-limb abnormality was seen in the CVS groups, but 1 child in the AC group had aplasia of the right hand. The two CVS approaches were compared among 2882 women at low and high genetic risk who were found to have cytogenetically normal fetuses. Rates of unintentional loss after the procedure were 7.7% for TC CVS and 3.7% for TA CVS (p < 0.001; 95% Cl of difference 2.3-5.8%). At baseline ultrasound scanning after establishment of optimum sampling conditions, more TC than TA procedures (p < 0.001) were judged not to be feasible. We found that TA CVS allows better access to the placental site than TC sampling, is an easier skill to acquire, and has the potential that more villi can be aspirated when needed. The risk of fetal loss is similar after TA CVS and AC. However, losses after AC are at a later stage and are therefore more distressing. TA procedures remain the first choice for prenatal diagnosis. Since, in our hands, TC sampling carries a greater risk to the fetus, we have abandoned TC CVS in our two study centres.

Cytogenetic results of chorionic villus sampling: high success rate and diagnostic accuracy in the United States collaborative study.

Cytogenetic results of first-trimester chorionic villus sampling are reported from seven U.S. medical centers. For 6033 patients who had a successful chorionic villus sampling procedure, the rate for obtaining a cytogenetic diagnosis was 99.6% with the direct method, long-term culture, or both. There were no incorrect sex predictions and no diagnostic errors involving trisomies 21, 18, or 13, sex chromosome aneuploidies, or structural abnormalities. There were no cases of normal cytogenetic diagnosis followed by birth of a cytogenetically abnormal infant. Three cases of unusual aneuploidies (tetraploidy, trisomy 16, and trisomy 22) detected by the direct method only were not confirmed by cytogenetic follow-up. Mosaic cytogenetic abnormalities were observed in 0.83% of all cases in which chorionic villus sampling was done but were confirmed by amniocentesis or in fetal tissues in only 7 of 30 cases (23.3%). Maternal cell contamination occurred in 1.9% of long-term cultures, although this did not present any cytogenetic diagnostic difficulties. Overall, a very high degree of laboratory success and diagnostic accuracy was observed with either cytogenetic method, although fewer predictive errors were observed with the long-term culture method and none were observed when both methods were used.

Sequential pathways of testing after first-trimester screening for trisomy 21

OBJECTIVE: To evaluate the performance and use of second-trimester multiple-marker maternal serum screening for trisomy 21 by women who had previously undergone first-trimester combined screening (nuchal translucency, pregnancy-associated plasma protein A, and free β-hCG), with disclosure of risk estimates. METHODS: In a multicenter, first-trimester screening study sponsored by the National Institute of Child Health and Human Development, multiple-marker maternal serum screening with alpha-fetoprotein, unconjugated estriol, and total hCG was performed in 4,145 (7 with trisomy 21) of 7,392 (9 with trisomy 21) women who were first-trimester screen-negative and 180 (7 with trisomy 21) of 813 (52 with trisomy 21) who were first-trimester screen-positive. Second-trimester risks were calculated using multiples of the median and a standardized risk algorithm with a cutoff risk of 1:270. RESULTS: Among the first-trimester screen-negative cohort, 6 of 7 (86%) trisomy 21 cases were detected by second-trimester multiple-marker maternal serum screening with a false-positive rate of 8.9%. Among the first-trimester screen-positive cohort, all 7 trisomy 21 cases were also detected in the second trimester, albeit with a 38.7% false-positive rate. CONCLUSION: Our data demonstrate that a sequential screening program that provides patients with first-trimester results and offers the option for early invasive testing or additional serum screening in the second trimester can detect 98% of trisomy 21–affected pregnancies. However, such an approach will result in 17% of patients being considered at risk and, hence, potentially having an invasive test. LEVEL OF EVIDENCE: II-2

Late First-Trimester Invasive Prenatal Diagnosis: Results of an International Randomized Trial

OBJECTIVE: To assess, in a randomized trial, the safety and accuracy of amniocentesis and transabdominal chorionic villus sampling (CVS) performed at 11–14 weeks of gestation, given that this time frame is increasingly relevant to early trisomy screening. METHODS: We compared amniocentesis with CVS from 77 to 104 days of gestation in a randomized trial in a predominantly advanced maternal age population. Before randomization, the feasibility of both procedures was confirmed by ultrasonography, and experienced operators performed sampling under ultrasound guidance; conventional cytogenetic analysis was employed. The primary outcome measure was a composite of fetal loss plus preterm delivery before 28 weeks of gestation in cytogenetically normal pregnancies. RESULTS: We randomized 3,775 women into 2 groups (1,914 to CVS; 1,861 to amniocentesis), which were comparable at baseline. More than 99.6% had the assigned procedure, and 99.9% were followed through delivery. In contrast to previous thinking, in the cytogenetically normal cohort (n = 3,698), no difference in primary study outcome was observed: 2.1% (95% confidence interval 1.5, 2.8) for CVS and 2.3% (95% confidence interval, 1.7, 3.1) for amniocentesis. However, spontaneous losses before 20 weeks and procedure-related, indicated terminations combined were increased in the amniocentesis group (P = .07, relative risk 1.74). We found a 4-fold increase in the rate of talipes equinovarus after amniocentesis (P = .02) overall and in week 13 (P = .03, relative risk = 4.65), but data were insufficient to determine this risk in week 14. CONCLUSION: Amniocentesis at 13 weeks carries a significantly increased risk of talipes equinovarus compared with CVS and also suggests an increase in early, unintended pregnancy loss. LEVEL OF EVIDENCE: I

Pregnancy-associated Plasma Protein A, Free β-hcg, Nuchal Translucency, and Risk of Pregnancy Loss

OBJECTIVE: To estimate the likelihood of clinical early and late pregnancy loss as a function of first-trimester maternal serum analytes and fetal nuchal translucency measurements. METHODS: Study subjects were recruited for a National Institute of Child Health and Human Development–sponsored multicenter cohort study initially designed to study the detection of Down syndrome during the first trimester of pregnancy. The cohort consisted of women who had a live fetus between 10 and 14 weeks of gestation and had no significant vaginal bleeding. Women with prior fetal trisomy (T21/18) and those with structural or chromosomal abnormalities in the index pregnancy were excluded. First-trimester screening consisted of pregnancy-associated plasma protein A (PAPP-A), free β-hCG, and nuchal translucency. Pregnancy loss rates in women with various levels of PAPP-A, free β-hCG, or nuchal translucency (less than 1st, less than 5th, more than 95th, and more than 99th percentile) were compared with losses in women with normal values (5th to 95th percentile). RESULTS: The mean gestational age at screening of 7,932 women meeting study criteria was 12.1 weeks. Loss rates were only 0.36% at less than 20 weeks after normal free β-hCG, PAPP-A, and nuchal translucency. Conversely, low levels of PAPP-A and free β-hCG as well as increased nuchal translucency were individually associated with increased early loss. These associations persisted after controlling for maternal age and race using logistic regression analysis. CONCLUSION: Normal values of PAPP-A, free β-hCG, and nuchal translucency are associated with a very low risk of pregnancy loss at less than 20 weeks. LEVEL OF EVIDENCE: II-2

Association of copy number variants with specific ultrasonographically detected fetal anomalies

OBJECTIVE: To evaluate the association of other-than-common benign copy number variants with specific fetal abnormalities detected by ultrasonogram. METHODS: Fetuses with structural anomalies were compared with fetuses without detected abnormalities for the frequency of other-than-common benign copy number variants. This is a secondary analysis from the previously published National Institute of Child Health and Human Development microarray trial. Ultrasound reports were reviewed and details of structural anomalies were entered into a nonhierarchical web-based database. The frequency of other-than-common benign copy number variants (ie, either pathogenic or variants of uncertain significance) not detected by karyotype was calculated for each anomaly in isolation and in the presence of other anomalies and compared with the frequency in fetuses without detected abnormalities. RESULTS: Of 1,082 fetuses with anomalies detected on ultrasound scan, 752 had a normal karyotype. Other-than-common benign copy number variants were present in 61 (8.1%) of these euploid fetuses. Fetuses with anomalies in more than one system had a 13.0% frequency of other-than-common benign copy number variants, which was significantly higher (P<.001) than the frequency (3.6%) in fetuses without anomalies (n=1,966). Specific organ systems in which isolated anomalies were nominally significantly associated with other-than-common benign copy number variants were the renal (P=.036) and cardiac systems (P=.012) but did not meet significance after the adjustment. CONCLUSIONS: When a fetal anomaly is detected on ultrasonogram, chromosomal microarray offers additional information over karyotype, the degree of which depends on the organ system involved. LEVEL OF EVIDENCE: II

Late first-trimester placental disruption and subsequent gestational hypertension/preeclampsia.

OBJECTIVE: To evaluate the potential relationship between placental disruption in weeks 13 and 14 and the subsequent development of gestational hypertension or preeclampsia. METHODS: Using subjects recruited during a randomized trial funded by the National Institute of Child Health and Human Development, which compared early amniocentesis and late transabdominal chorionic villus sampling (CVS) in weeks 13 and 14, rates of gestational hypertension and preeclampsia were compared between cases with varying degrees of placental disruption. RESULTS: A total of 3,698 of 3,775 randomized subjects had cytogenetically normal pregnancies and were analyzed. A significantly higher rate of hypertension/preeclampsia was observed in the late CVS group (5.4%, n = 1,878) compared with the early amniocentesis cohort (3.5%, n = 1,820; P = .005). This difference persisted after controlling for maternal age, body mass index, parity, previous preterm delivery, smoking, and fetal gender. Early amniocentesis cases were further stratified on the basis of whether the placenta had been penetrated (n = 460) or not (n = 1,360). Risk of hypertensive complications was lowest if the placenta was not traversed (3.4%), greater with placental penetration (3.9%), and highest when the placenta was directly sampled during CVS (5.4%, P = .02). CONCLUSION: We hypothesize that focal disruption of the placenta at 13–14 weeks may increase the risk of hypertension/preeclampsia. These findings provide support for the theory that disturbances in early placentation lead subsequently to maternal hypertension. LEVEL OF EVIDENCE: II-1

Progestogens to prevent preterm birth in twin pregnancies: an individual participant data meta-analysis of randomized trials

BackgroundPreterm birth is the principal factor contributing to adverse outcomes in multiple pregnancies. Randomized controlled trials of progestogens to prevent preterm birth in twin pregnancies have shown no clear benefits. However, individual studies have not had sufficient power to evaluate potential benefits in women at particular high risk of early delivery (for example, women with a previous preterm birth or short cervix) or to determine adverse effects for rare outcomes such as intrauterine death.Methods/designWe propose an individual participant data meta-analysis of high quality randomized, double-blind, placebo-controlled trials of progestogen treatment in women with a twin pregnancy. The primary outcome will be adverse perinatal outcome (a composite measure of perinatal mortality and significant neonatal morbidity). Missing data will be imputed within each original study, before data of the individual studies are pooled. The effects of 17-hydroxyprogesterone caproate or vaginal progesterone treatment in women with twin pregnancies will be estimated by means of a random effects log-binomial model. Analyses will be adjusted for variables used in stratified randomization as appropriate. Pre-specified subgroup analysis will be performed to explore the effect of progestogen treatment in high-risk groups.DiscussionCombining individual patient data from different randomized trials has potential to provide valuable, clinically useful information regarding the benefits and potential harms of progestogens in women with twin pregnancy overall and in relevant subgroups.

Impacts of variants of uncertain significance on parental perceptions of children after prenatal chromosome microarray testing

There are concerns regarding the potential harms in receipt of prenatal chromosome microarray (CMA) results, particularly variants of uncertain significance (VUS). We examined the influence that the return of genomic results had on parental well‐being and perceptions of childrens development.