A prospective study of spontaneous miscarriage in ultrasonically normal pregnancies and relevance to chorion villus sampling

Miscarriage risk from amniocentesis performed for abnormal maternal serum screening

OBJECTIVE

The purpose of this study was to evaluate miscarriage after mid-trimester amniocentesis for abnormal maternal serum screening.

STUDY DESIGN

An analysis of summary data from the California State maternal serum screening program on 32,050 women with an abnormal serum screen, a singleton fetus, and normal ultrasound was performed. Miscarriage before 24 weeks, days until miscarriage, gestational age at miscarriage, and maternal factors were compared. The power of this study could detect a 50% increase in miscarriage.

RESULTS

The miscarriage rate with amniocentesis, 0.46% (69/15,005), was no different than without, 0.53% (90/17,045), P = .38. There was no difference in maternal age, serum biochemical factors, gestational age at miscarriage (21.1 weeks for both groups), or days until miscarriage (23 after amniocentesis and 20.4 without). Log-rank test revealed no difference for gestational age at miscarriage (P = .61) or number of days until miscarriage (P = .40).

CONCLUSION

The rate and timing of miscarriage was similar with or without amniocentesis in California women with abnormal maternal serum screening.

A longitudinal study of pregnancy outcome following idiopathic recurrent miscarriage

Recurrent miscarriage is a difficult clinical problem occurring in approximately 1-2% of fertile women. Following investigation, most cases fail to reveal an identifiable cause and are therefore classified as idiopathic. The aim of this study was to identify important gestational milestones for pregnancy success prediction in women following idiopathic recurrent miscarriage. A total of 325 consecutive patients with idiopathic recurrent miscarriage was involved in a prospective longitudinal observational study. Patients were identified from a miscarriage database of 716 patients. Preconceptual presentation and investigation excluded patients from the study sample with known associations of recurrent pregnancy loss, such as antiphosholipid syndrome, oligomenorrhoea, mid-trimester loss and other rare causes, e.g. abnormal parental karyotype. Following early presentation in a subsequent pregnancy, all patients followed a standard clinic protocol including fetal viability ultrasonography on a fortnightly basis throughout the first trimester. Kaplan-Meier curves were constructed for pregnancy outcome. Out of 325 idiopathic cases, 70% (n = 226) conceived, with a 75% success rate. Of 55 miscarriages, longitudinal assessment showed that six losses occurred following detection of fetal cardiac activity (3%). Data from this large study group have enabled accurate prediction of future pregnancy success and have established important gestational milestones for women with idiopathic recurrent miscarriage.

First trimester prenatal diagnosis: amniocentesis

Twenty years after midtrimester genetic amniocentesis was first used, first trimester invasive prenatal procedures were introduced. Chorionic villous sampling presents some disadvantages that entitled many centers to look into an alternative for first trimester diagnosis. Early amniocentesis (EA) can be performed effectively, as shown over the years in many observational studies and partially randomized and randomized trials. Recently, a multicenter randomized trial (Canadian Early and Midtrimester Amniocentesis Trial) reported a higher total pregnancy loss, a significant increased incidence of musculoskeletal foot deformities, a significant increased culture failure rate, and an increased postamniocentesis rate of leakage in the EA group compared with midtrimester amniocentesis. These results concerning EA procedures from 11w(+0) to 12w(+6) should be included in any pre-EA counseling. However, further trials have started to evaluate EA procedures between 13w(+0) to 14w(+6).

Experience with 1251 transcervical chorionic villus samplings performed in the first trimester by a single team of operators

OBJECTIVE

We report our experience with 1251 chorionic villus samplings (CVS) performed by a single team of operators.

STUDY DESIGN

From April 1984 through August 1993, 1251 CVS were performed in 1236 pregnancies. The transcervical route was used in the vast majority and the sampling was performed during the 9th through 13th weeks of gestation in 1193 cases (96%). Follow-up was ensured to tabulate the pregnancy-related complications and fetal loss rate until 28 weeks' gestation. Pregnancy outcome was documented for all but 36 women (3%).

RESULTS

Most of the tests (72%-891/1236 pregnancies) were performed for advanced maternal age (> or = 35 years). The percentage of each indication remained relatively stable, around 90% for chromosomal indications and between 8 and 11% for DNA studies. Samples adequate for diagnosis were obtained in one or two sessions in 1179 pregnancies (95%). The rate of spontaneous abortion possibly related to CVS was 2.5% (28/1092). Mosaicism confined to the placenta was found in 23 cases (1.8%). The pregnancy outcome was known in 1098 pregnancies. There were 10 perinatal losses (0.9%) and nine congenital malformations (0.8%). No transverse limb defects were observed. The rate of premature deliveries (4.6%) and of small for gestational age were comparable to the general uninstrumented population.

CONCLUSION

CVS is a safe and effective mode of antenatal diagnosis when performed by a single team of experienced operators.

Risk assessment of amniocentesis between 11 and 15 weeks: comparison to later amniocentesis controls

We studied 693 consecutive early amniocenteses (prior to 15 weeks) and found a spontaneous abortion rate to 28 weeks' gestation of 1.5 per cent. A control group of women having standard amniocentesis (15-20 weeks) experienced a 0.6 per cent fetal loss in the same period. There were no other apparent differences between the two groups. Early amniocentesis results are generally available 4-6 weeks before standard amniocentesis and 1-3 weeks after chorionic villus sampling (CVS). Alpha-fetoprotein (AFP) can be accurately assayed in 11- to 15-week amniotic fluid samples but additional studies are necessary to determine the accuracy of neural tube defect (NTD) detection. Including the present study, over 5800 early amniocenteses have been reported and the results suggest that this is a relatively safe prenatal diagnostic test and an alternative to CVS and later amniocentesis.

Comparison of first-trimester transvaginal amniocentesis with chorionic villus sampling and mid-trimester amniocentesis

Between August 1989 and December 1991, 356 patients underwent first-trimester transvaginal amniocentesis (10-12 weeks). The same number of patients referred in the same period for mid-trimester amniocentesis (14-21 weeks) was matched also for maternal age and indication. A third group consisted of the first 356 cases in which chorionic villus sampling (CVS) was attempted. The overall success rate was 99.7 and 100 per cent for early and mid-trimester amniocentesis, respectively, and 97.2 per cent for CVS. The mean harvesting time was 12.8, 11, and 7.9 days, respectively. The percentage of patients rescheduled was 3.4 per cent in first-trimester amniocentesis, 1.7 per cent in mid-trimester amniocentesis, and 6.2 per cent in the CVS group. The early (less than 2 weeks) pregnancy loss was 1.7 and 0.6 per cent in early and mid-trimester amniocentesis, respectively, and 1.7 per cent in CVS. The total pregnancy loss was 3.2, 0.9, and 2.9 per cent, respectively. The rate of preterm birth was 6.0, 5.2 and 6.9 per cent, respectively. The results indicate that CVS has the shortest procedure-result interval, but the highest rescheduling rate. First-trimester amniocentesis has a higher procedure and laboratory success rate but, until otherwise proved, mid-trimester amniocentesis is the most efficient and safest procedure.

Transabdominal chorionic villus sampling: fetal loss rate in relation to maternal and gestational age

In this paper we report the fetal loss rate in relation to both maternal and gestational age in 1764 pregnant women who underwent transabdominal chorionic villus sampling (TA-CVS) between January 1986 and August 1990. The fetal loss rate, considered as a proportion of continuing pregnancies, decreased with advancing gestational age at sampling from 4.3 per cent before 9 weeks to 0.4 per cent at or after 13 weeks, the difference being statistically significant (p < 0.025). The fetal loss rate increased from 1.6 per cent in women under 30 to 2.4 per cent in women of 40 years or over, but the difference was not statistically significant. Considering that the total fetal loss rate before 28 weeks' gestation was on average 1.91 per cent (1.3 per cent under 35 years and 2.8 per cent in women of 35 or over), we believe that TA-CVS is a safe and effective technique for prenatal diagnosis of genetic diseases.

Early amniocentesis: outcome, risks, and technical problems at less than or equal to 12.8 weeks

OBJECTIVE

It is the purpose of this report to evaluate our experience with amniocentesis at less than or equal to 12 weeks' gestation.

STUDY DESIGN

Medical records of 936 patients at less than or equal to 12.8 weeks' gestation undergoing genetic amniocentesis between Oct. 1, 1986, and June 30, 1990, were evaluated for gestational age, indication, frequency of needle insertion, amniocentesis complications, and pregnancy outcome.

RESULTS

There were seven miscarriages within 2 weeks of amniocentesis (0.7%), 21 miscarriages before 28 weeks (2.2%), and four stillbirths or neonatal deaths (0.4%), resulting in a total postprocedural loss rate of 3.4%. There were 26 chromosomally abnormal fetuses (2.8%). The spontaneous abortion rate in ultrasonographically normal pregnancies at less than 14 weeks, not undergoing amniocentesis, has been estimated at 2.1% to 3.2%.

CONCLUSION

Amniocentesis at 12 weeks is a viable option for patients desiring earlier prenatal genetic diagnostic information.

Amniocentesis or chorionic villus sampling for prenatal genetic testing: a decision analysis

We used decision analysis to examine the strategies of amniocentesis, chorionic villus sampling, and no prenatal testing for a pregnant woman who would be 35 years of age at the expected date of delivery. Probabilities were obtained from the obstetric and genetic literature, and utilities from previously published standard reference gambles and from responses of obstetric residents and students recorded on a linear rating scale. The expected utility of amniocentesis exceeded that of chorionic villus sampling by 0.1 utility units, and of no prenatal testing by 0.12 utility units. The decision was insensitive to clinically plausible values for the probabilities of spontaneous abortion after amniocentesis and chorionic villus sampling, the probabilities of abnormal and indeterminate chorionic villus sampling results, the probability of an abnormal amniocentesis result after an indeterminate chorionic villus sampling, the sensitivities and specificities of amniocentesis and chorionic villus sampling, and the probabilities of significant maternal morbidity after first- and second-trimester therapeutic abortion. Chorionic villus sampling was preferred to amniocentesis when the utility of a first-trimester therapeutic abortion exceeded that of a second-trimester abortion by 23.2 utility units, or when the anxiety "cost" of awaiting second-trimester amniocentesis results exceeded 0.1 utility unit. We conclude that over a range of assumptions concerning the probabilities involved in the prenatal testing decision, amniocentesis was preferred to chorionic villus sampling. However, for a decision maker for whom a second-trimester therapeutic abortion would be significantly less acceptable than a first-trimester procedure, or for whom the anxiety of awaiting second-trimester chromosomal diagnosis might be an important consideration, chorionic villus sampling could become the procedure of choice.

Predicting pregnancy outcome by the observation of a gestational sac or of early fetal cardiac motion with transvaginal ultrasonography

Transvaginal ultrasound (US) allows for observation of the gestational sac and cardiac motion as early as 3 and 4 weeks after ovulation, respectively. The purpose of this study was to determine how well the first observation of cardiac motion, using weekly transvaginal US examinations, predicted pregnancy outcome. Three hundred sixteen pregnancies wherein the date of ovulation was known and a single gestational sac was visualized at 3 weeks after ovulation were studied. Cardiac motion was first detected at 4 weeks after ovulation in 226 (71.5%), and at 5 weeks in 67 (21.2%). In 23 patients, cardiac motion was never observed. In those patients with cardiac motion visible at 4 weeks after ovulation, 94.2% have subsequently delivered viable infants. This contrasts with only 70.1% for those patients who first had observable cardiac motion 1 week later (P = 6.7 X 10(-6]. This study demonstrates that the solo finding of a gestational sac is a poor predictor of pregnancy outcome (82.3% accurate) and that the earlier that cardiac motion is initially observed, the better the pregnancy prognosis.

Spontaneous abortion rate and advanced maternal age: consequences for prenatal diagnosis

Maternal age related and procedure-related fetal abortion rates were studied in 384 women aged 36 and over scheduled for transabdominal chorionic villus sampling (TA-CVS) at 12-14 weeks of gestation. The pre-TA-CVS abortion rate within 30 days of intake (at 6-10 weeks of gestation) rose from 1.9% at age 35-36 years to 10.9% at 40 years and older. Women entering in the 6th week of gestation had a greater probability of aborting before TA-CVS than women entering after day 48. 26 women aborted spontaneously before TA-CVS, the majority of abortions occurring at 10-12 weeks. TA-CVS was done in 346 women. 11 pregnancies were terminated because of genetic anomalies, and 8 women had spontaneous fetal loss. These findings justify delaying prenatal diagnosis in older pregnant women until 12 weeks of gestation.

Ultrasonography-guided early amniocentesis in singleton pregnancies

Between October 1, 1986, and September 30, 1987, 1721 amniocenteses were performed at the University of California, Davis, Medical Center. Of these procedures 527 (30.6%) were early amniocenteses. Medical records were reviewed for maternal age, amniocentesis indication, color of amniotic fluid, gestational age, frequency of needle insertion, complications of amniocentesis and delivery, results of prenatal testing, and pregnancy outcome. Complete follow-up data were available for 517 (98.1%). There were 10 miscarriages before 28 weeks' gestation (1.9%), one loss after 28 weeks (0.2%), and one stillbirth (0.2%), resulting in a total postprocedural loss rate of 2.3%. Miscarriage within 2 weeks of amniocentesis occurred in four subjects (0.8%).

Transabdominal villus sampling in early second trimester: a safe sampling method for women of advanced age

Transabdominal chorionic villus sampling (TA-CVS) was performed in 707 viable singleton pregnancies to exclude chromosomal abnormalities. Maternal age ranged between 36 and 49 years (mean 37.9 years); gestational age varied between 10.2 and 18.3 weeks (mean 13.3 weeks). In 639 women (90.4 per cent), a sufficient amount of chorionic tissue (greater than or equal to 10 mg) was obtained after one needle insertion; in 66 women (9.3 per cent) two insertions were needed. An abnormal chromosome pattern was established in 19 cases (2.9 per cent). Vaginal bleeding or spotting within 28 days after TA-CVS occurred in 11 cases (1.5 per cent). The completed follow-up of 678 chromosomally normal pregnancies showed an overall fetal loss rate of 2.6 per cent before 28 weeks. The overall perinatal mortality was 0.9 per cent. When relating fetal loss to gestational age at TA-CVS, this was 6.6 per cent in women sampled before 12 weeks against only 1.8 per cent after 12 weeks. At the same time, the percentage of fetal loss occurring within 2 weeks following the procedure was 75 and 30 per cent, respectively. It is suggested that these data reflect the decline in spontaneous abortion rate during this particular period of pregnancy. It is concluded that TA-CVS is an effective procedure which, when performed after the natural decrease of fetal loss, appears to be a safe option for women of advanced maternal age.

Current assessment of fetal losses as a direct consequence of chorionic villus sampling

Chorionic villus sampling has been developed as a method of first trimester prenatal diagnosis. In order to evaluate this new approach, accurate risk figures for the procedure must be obtained. This has been difficult for a number of reasons, including establishment of baseline fetal loss rates in the first trimester, procedural "learning curves," and reporting biases. This review will discuss these problems and use data from the chorionic villus sampling program at the University of California, San Francisco, to illustrate difficulties in data interpretation.

Integration of the transabdominal technique into an ongoing chorionic villus sampling program

Data are presented on 869 patients undergoing chorionic villus sampling procedures by one of two sampling techniques: 544 by a transcervical catheter aspiration method and 325 by a transabdominal two-needle aspiration method. The transcervical approach was the only procedure used in the first 330 cases, at which time the transabdominal technique was incorporated into our program. After an initial learning curve in the first 100 procedures the transcervical fetal loss rate stabilized at 2.7%, the number of patients requiring more than one catheter insertion decreased to 11%, and tissue weights greater than or equal to 10 mg were obtained in 88% of cases. The fetal loss rate for transabdominal chorionic villus sampling was 2.6%, indicating the addition of this new method did not significantly alter the fetal loss rate. Transabdominal chorionic villus sampling had an overall success rate of 99%, with only one insertion of the guide needle required for 98% of patients. Tissue weights of greater than or equal to 10 mg were obtained in 99% of cases. These results demonstrate that the transabdominal procedure can be rapidly and effectively incorporated by an operator already experienced with transcervical chorionic villus sampling. Since several contraindications exist for either chorionic villus sampling method, the availability of both techniques at a single center greatly enhances the ability to offer first-trimester fetal diagnosis to a majority of patients.

Bleeding as a consequence of chorion villus sampling

A series of 4 separate studies were conducted to assess the incidence and short term consequence of bleeding associated with chorion villus sampling. Results support previous reports that risk of foetal-maternal transfusion as suggested by a rise in maternal serum alpha-fetoprotein (MSAFP) can occur. This occurrence is not consistent and need not be obvious even after therapeutic abortion. It is also transient and did not complicate mid-trimester neural tube screening or subsequent course of pregnancy. Eighty-seven percent of blood contaminating villus samples are of maternal origin. Following diagnosis 37% of patients reported some vaginal bleeding. This is mainly in the form of spotting which did not preclude normal pregnancy. Foetal loss occurred in 4 of the patients when bleeding considered heavier than spotting continued. In rhesus negative patients prophylactic anti-D gamma-globulin is advised, since neither Kleihauer counts nor MSAFP estimation reliably detect all foetal-maternal transfusions.