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Historical aspects of genetic counseling: why was maternal age 35 chosen as the cut-off for offering amniocentesis?

The justification for offering amniocentesis to women age 35 or older is that by age 35 the risk of having a child with chromosome problem is greater than the risk of amniocentesis. In fact, this seemingly objective statement is not supported by historical analysis. Maternal age 35 was chosen for the cutoff based mostly on economic cost-benefit analysis rather than objective medical assessment. The story of why 35 was chosen illustrates how collective memory can affect, and be influenced by, the guiding ethical principles of a medical profession.

Age Factors↗

The sensitivity of the trivariate analysis using maternal serum alpha-feto protein, human chorionic gonadotrophin and maternal age in screening for fetal aneuploidy in mothers above the age of 35.

This study was undertaken to assess the usefulness of maternal serum human chorionic gonadotrophin, alpha-fetoprotein and maternal age in screening for fetuses with abnormal chromosomes in pregnant women aged 35 years and over. From 1989 to 1991, 1208 women seen at the National University Hospital had karyotyping procedures performed for maternal age > 35 years as well as second trimester serum samples taken for alpha-fetoprotein and human chorionic gonadotrophin. Sixteen (1.3%) chromosomal abnormalities were present. Using cut off risk levels of 1:250 and 1:384, the sensitivity of the analysis in screening for Down's syndrome pregnancies was 71.5% and 86% respectively. For the non Down's chromosomal abnormalities, using cut off risk levels of 1:250 and 1:384, the sensitivity of the analysis was only 22.3% and 33.4% respectively. Thus risk calculations based on the two serum markers and maternal age failed to identify all fetuses with abnormal chromosomes.

Adult↗

Aneuploidy in twin gestations: when is maternal age advanced?

OBJECTIVE: To determine the maternal age at which twin gestations have a risk of fetal aneuploidy comparable to that of singleton pregnancies at maternal age 35, accounting for variation in dizygotic twinning rates by maternal age and race. METHODS: Known aneuploidy risks and rates of dizygotic twinning by maternal age and race were used to calculate the risk of fetal aneuploidy at term and in the second trimester by maternal age and race in twin gestations, using previously published calculations. RESULTS: The risk of at least one aneuploid twin at term is 1/193 at maternal age 31 for both white and African-American women, which is comparable to the risk of 1/192 for an aneuploid singleton term pregnancy at maternal age 35. The risk of at least one aneuploid twin at amniocentesis at maternal age 31 is 1/190 for white and 1/187 for African-American women, which is slightly lower than the rate in singletons of 1/135. CONCLUSION: Invasive prenatal diagnosis for detection of fetal aneuploidy should be offered to all women with twin gestations at age 31, regardless of race.

Adult↗

Down syndrome: clinical and cytogenetic analysis.

OBJECTIVE: To describe the clinical features and cytogenetic analysis of patients with Down syndrome (DS). DESIGN: An observational study. PLACE AND DURATION OF STUDY: The Departments of Paediatrics and Internal Medicine of Military Hospital, Rawalpindi (MH, RWP) from January 1998 to December 2001. PATIENTS AND METHODS: Two hundred and ninety-five children <18 years of age clinically diagnosed as DS were included. The clinical presentation features, associated anomalies and maternal characteristics were noted. RESULTS: Out of 295, 170 boys and 125 girls had chromosomal findings consistent with the diagnosis of DS. The mean presentation age was 16.2 months while 49 (16.6%) children presented in the neonatal period and 124 (42%) in infancy. Mongoloid slant, epicanthal folds, hypertelorism, simian crease, flat nasal bridge, and microcephaly were observed in >60% of cases. Congenital heart disease was documented in 103 (34.9%) cases and ventricular septal defect was the commonest cardiac anomaly. The cytogenetic analysis revealed that 282 (95.6%) had trisomy 21, 11(3.7%) had translocation, and only 2(0.7%) were mosaic. The mean maternal age was 29.8 years. One hundred and sixty (56.7%) cases with trisomy 21 had maternal age> 35 years, whereas 9/11(81.8%) cases of translocation had maternal age < 35 years. CONCLUSION: The cytogenetic pattern of DS was similar to previously described series. Inadequate antenatal screening and scarce neonatal examination results in late presentation of DS. Majority of cases can be diagnosed on the clinical features of DS.

Down Syndrome↗

Pregnancy outcome distribution and prenatal diagnosis of autosomal abnormalities, Hawaii, 1986-1999.

BACKGROUND: Approximately 10% of birth defects result from chromosomal abnormalities. This study investigated the pregnancy outcome distribution of autosomal abnormalities and impact of prenatal diagnosis on autosomal abnormalities. METHODS: Data were obtained from a population-based birth defects registry and included all autosomal abnormalities delivered in Hawaii during 1986-1999. RESULTS: There were 1,015 autosomal abnormality cases, consisting of 523 (52%) live births, 38 (4%) late fetal deaths, 187 (18%) early fetal deaths, 265 (26%) elective terminations, and 2 unknown pregnancy outcome. Live births comprised the majority of translocations (81%), inversions (93%), and deletions (84%) but a smaller proportion of trisomies (42%). Autosomal abnormalities were prenatally diagnosed in 489 (48%) of the cases, of which 243 (50%) were subsequently electively terminated. By type of autosomal abnormality, prenatal diagnosis rates were trisomy (44%), translocation (68%), inversion (91%), deletion (29%), and subsequent elective termination rates were trisomy (73%), translocation (11%), inversion (4%), deletion (50%). The prenatal diagnosis rate was higher for maternal age 35 years or greater than for maternal age less than 35 years (relative risk (RR) 1.8, 95% confidence interval (CI) 1.6-2.0), as was the elective termination rate (RR 1.3, 95% CI 1.1-1.6). The prenatal diagnosis rate was higher in 1993-1999 than in 1986-1992 (RR 1.2, 95% CI 1.1-1.4), although there was no statistically significant difference between the two time periods for subsequent elective termination rate (RR 0.9, 95% CI 0.8-1.1). CONCLUSIONS: Pregnancy outcome distribution, prenatal diagnosis rates, and subsequent elective terminations rates vary by type of autosomal abnormality.

Abortion, Legal↗

The 75-gram glucose load in pregnancy: relation between glucose levels and anthropometric characteristics of infants born to women with normal glucose metabolism.

OBJECTIVE: To investigate, in pregnant women without gestational diabetes mellitus (GDM), the relation among obstetric/demographic characteristics; fasting, 1-h, and 2-h plasma glucose values resulting from a 75-g glucose load; and the risk of abnormal neonatal anthropometric features and then to verify the presence of a threshold glucose value for a 75-g glucose load above which there is an increased risk for abnormal neonatal anthropometric characteristics. RESEARCH DESIGN AND METHODS: The study group consisted of 829 Caucasian pregnant women with singleton pregnancy who had no history of pregestational diabetes or GDM, who were tested for GDM with a 75-g, 2-h glucose load, used as a glucose challenge test, in two periods of pregnancy (early, 16-20 weeks; late, 26-30 weeks), and who did not meet the criteria for a GDM diagnosis. In the newborns, the following abnormal anthropometric characteristics were considered as outcome measures: cranial/thoracic circumference (CC/TC) ratio </=10th percentile for gestational age (GA), ponderal index (birth weight/length(3) x 100) >/=90th percentile for GA, and macrosomia (birth weight >/=90th percentile for GA), on the basis of growth standard development for our population. For the first part of the objective, logistic regression models were used to identify 75-g glucose load values as well as obstetric and demographic variables as markers for abnormal neonatal anthropometric characteristics. For the second part, the receiver operating characteristic (ROC) curve was performed for the 75-g glucose load values to determine the plasma glucose threshold value that yielded the highest combined sensitivity and specificity for the prediction of abnormal neonatal anthropometric characteristics. RESULTS: In both early and late periods, maternal age >35 years was a predictor of neonatal CC/TC ratio </=10th percentile and macrosomia, with fasting 75-g glucose load values being independent predictors of neonatal CC/TC ratio </=10th percentile. In both periods, 1-h values gave a strong association with all abnormal neonatal anthropometric characteristics chosen as outcome measures, with maternal age >35 years being an independent predictor for macrosomia. The 2-h, 75-g glucose load values were significantly associated in both periods with neonatal CC/TC ratio </=10th percentile and ponderal index >/=90th percentile, whereas maternal age >35 years was an independent predictor of both neonatal CC/TC ratio </=10th percentile and macrosomia. In the ROC curves for the prediction of neonatal CC/TC ratio </=10th percentile for GA in both early and late periods of pregnancy, inflection points were identified for a 1-h, 75-g glucose load threshold value of 150 mg/dl in the early period and 160 mg/dl in the late period. CONCLUSIONS: This study documented a significant association, seen even in the early period of pregnancy, between 1-h, 75-g glucose load values and abnormal neonatal anthropometric features, and provided evidence of a threshold relation between 75-g glucose load results and clinical outcome. Our results would therefore suggest the possibility of using a 75-g, 1-h oral glucose load as a single test for the diagnosis of GDM, adopting a threshold value of 150 mg/dl at 16-20 weeks and 160 mg/dl at 26-30 weeks.

Blood Glucose↗

Maternal mortality in Nigerian women aged 35 years and above.

Maternal deaths over a 5-year period were reviewed retrospectively. The aim was to compare the incidence and causes of maternal deaths and the fetal outcome in women aged 35 years and above with women in the 20-24 age bracket. The classic triad of haemorrhage, sepsis and hypertensive disorders were the major causes of deaths in the 2 groups but were commoner amongst the elderly women. A higher incidence of perinatal mortality was also found in the elderly women's group compared to the younger women's group. Pregnancy and delivery at an advanced age is associated with increased risk and should be prevented by the use of effective contraception.

Adult↗

A survey of attitudes about maternal serum screening for fetal chromosome abnormalities in women 35 years of age and older.

We asked two groups of women their opinion on prenatal diagnosis and maternal serum screening (MSS): group 1 comprised women who had undergone a prenatal diagnostic procedure (amniocentesis or chorionic villus sampling) for advanced maternal age (>/=35 years) and group 2 women who had undergone MSS and were 30-34 years old. Women in group 1 were found significantly less likely to choose MSS over prenatal diagnosis than were women in group 2. The sensitivity of MSS and the age-related risk of chromosome abnormalities influenced opinions on whether to choose MSS or prenatal diagnosis. In both groups, the majority stated that they would accept MSS over prenatal diagnosis, if their obstetrician recommended it.

Adult↗

Prenatal diagnosis in 3,000 women for chromosome, X-linked, and metabolic disorders.

In 3,000 women referred for prenatal diagnosis, 110(3.7%) abnormal fetuses were detected and 85 therapeutic terminations were performed. These were five main reasons for referral. Among the 2,227 women referred because of maternal age 35 years and older, there were 51 (2.3%) who had aneuploid fetuses. In the 297 women referred because of a previous child with Down syndrome, 3 aneuploid fetuses (1.0%) were detected. Of the 55 couples where one spouse was a carrier of a balanced chromosome rearrangement, 6 chromosomally abnormal fetuses were found (10.9%) (all the offspring of maternal carriers). In the latter group, five of the six heterozygotes with abnormal findings were carriers of tdic (13;21) translocations. In the 82 cases with a history of X-linked disorders, there were 40 males (49%). Thirty-five women were referred because of inborn errors of metabolism: 10 affected fetuses were found (28%). There was a greater proportion of sex-chromosome aneuploids as compared to trisomy 21 fetuses in the 35 to 39 year maternal age group. This was reversed in the group of women 40 years old and older. Of the 25 abnormal fetuses not terminated, 6 were sex chromosome aneuploids and 10 involved X-linked conditions where the progeny could be further prenatally monitored (eg, X-linked hydrocephalus) or treated (eg, hemophilia). In the remaining 9 the parents expressed divers reasons for their choice. Repeat amniocentesis was required in 2.9% of cases. One case of maternal cell contamination and one case of unconfirmed mosaicism were the only diagnostic errors found in the study. In the last 1,000 specimens referred, the average time necessary for a karyotypic result was 15.6 +/- 5.6 days after amniocentesis.

Abortion, Induced↗

Efficacy of screening for fetal Down syndrome in the United States from 1974 to 1997.

OBJECTIVE: To estimate the 16-week prevalence of Down syndrome in the United States from 1974 to 1997 and to determine the efficacy of maternal age cutoffs and triple screens for detecting it antenatally. METHODS: Using natality statistics for the United States from 1974 to 1997 of maternal-age-specific live births to women 13-49 years old, we evaluated advanced maternal age (35-49 years at delivery) and the triple serum test (maternal serum alpha-fetoprotein, hCG, and unconjugated estriol) as screening tests for Down syndrome. Efficacy was evaluated using sensitivity, false-positive rate, positive predictive value, and likelihood ratio (likelihood ratio = sensitivity/false-positive rate). RESULTS: In 1974, the estimated second-trimester prevalence of Down syndrome was one in 740, but by 1997 that had increased to one in 504. The proportion of Down syndrome fetuses at 16 weeks' gestation in women 35-49 years old increased from 28.5% in 1974 to 47.3% in 1997. However, live births to women 35-49 years old increased more rapidly from 4.7% in 1974 to 12.6% in 1997. The likelihood ratio for maternal age to identify an affected pregnancy decreased during the study period and was substantially lower than that using the serum test. CONCLUSION: A maternal age cutoff of 35 years in the 1990s resulted in high false-positive rates and was less efficacious based on likelihood ratio and positive predictive value. Serum testing of all pregnant women would reduce the number of amniocenteses and decrease procedure-related losses.

Adolescent↗

Use of prescription drugs in the first trimester and congenital malformations.

A prospective survey of prenatal use of prescription drugs in Tasmania yielded detailed information on drug exposure, delivery and outcome for 56,037 births from 1982 to 1989. First trimester drug use was reported by 30.9% of women, and 17.9% used only supplements of vitamins and/or minerals; 40% used alcohol during the first trimester, and 28.8% smoked cigarettes. There were 1,035 (1.85%) congenital malformations, of which 885 (85.5%) were major. The malformation rate was not significantly different in the following exposure categories: supplements only (1.62%); other pharmaceuticals (1.92%); smokers (1.88%); alcohol users (1.89%); and maternal age 35 or more years (1.95%). Adjusting for alcohol use, smoking, maternal age and diabetes mellitus, significant associations [expressed as adjusted odds ratio and 95% confidence intervals (CI)] were found between aspirin and hypospadias (3.5, 95% CI 1.4 to 8.8); dicyclomine and phocomelia (4.4, 95% CI 1.0 to 19.5); and between oral contraceptive use and pes cavus (9.7, 95% CI 2.3 to 40.4). Although significant, these associations were based on very few cases and no direct supporting evidence could be found from other data sources.

Abnormalities, Drug-Induced↗

Impact of labor induction, gestational age, and maternal age on cesarean delivery rates.

OBJECTIVE: To quantify the impact of labor induction and maternal age on cesarean delivery rates in nulliparous and multiparous women between 36 and 42 weeks' gestation. METHODS: We performed a retrospective cohort study on 14,409 women delivering at two teaching hospitals in metropolitan Boston during 1998 and 1999. Women who had contraindications to labor, including a prior cesarean delivery, were excluded. The risks for cesarean delivery by induction status, gestational age by completed week between 36 and 42 weeks, maternal age <35, 35-39, and >/=40 years, and stratified by parity, were calculated by logistic regression. RESULTS: In nulliparas, labor induction was associated with an increase in cesarean delivery from 13.7% to 24.7% (adjusted odds ratio [OR] 1.70; 95% confidence interval [CI] 1.48, 1.95]). In multiparas, induction was associated with an increase from 2.4% to 4.5% (OR 1.49; 95% CI 1.10, 2.00). Other variables that placed a nulliparous woman at increased risk for cesarean delivery included maternal age of at least 35 years and gestational ages over 40 weeks. For multiparas, only maternal age 40 years or older and gestational age of 41 weeks were associated with an increase in cesarean deliveries. CONCLUSION: Induction of labor, older maternal age, and gestational age over 40 weeks each independently increase the risk for cesarean delivery in both nulliparous and multiparous women. Although the relative risk from induction is similar in nulliparas and multiparas, the absolute magnitude of the increase is much greater in nulliparas (11% versus 2.1%).

Adult↗

Manual rotation of the fetal occiput: predictors of success and delivery.

OBJECTIVE: The purpose of the study was to define predictors of successful rotation and rate of cesarean delivery after manual rotation of the fetal occiput from occiput posterior or transverse position. STUDY DESIGN: A retrospective cohort study comprised patients who underwent a trial of manual rotation of the fetal occiput from occiput posterior or occiput transverse position. Successful rotation was defined as delivery in the occiput anterior position. We examined maternal, fetal, and labor characteristics as predictors of both fetal position at delivery and cesarean delivery. RESULTS: Multiparity (odds ratio, 2.5; 95% CI, 1.5-3.8) and maternal age < 35 years (odds ratio, 2.0; 95% CI, 1.1-3.4) were associated with successful manual rotation of the fetal occiput. After successful rotation, the cesarean delivery rate was 2%, compared with 34% if the rotation failed (P < .001). Asian ethnicity, nulliparity, age > 35 years, labor induction, and epidural usage were associated with higher rates of cesarean delivery. CONCLUSION: After successful manual rotation of the fetal occiput, women had lower cesarean delivery rates than women with unsuccessful rotations. Multiparity and maternal age of < 35 years were associated with more successful rotations.

Adult↗

[The monitoring of cleft lip with or without cleft palate in China: 1996 - 2000].

OBJECTIVE: To describe the epidemiological features of cleft lip with or without cleft palate (CL +/- P) in Chinese perinatals. METHODS: From 1996 through 2000, hospital-based cluster sampling method was adopted for collecting data. During that period all live or still births with 28 weeks of gestation or more delivered in monitoring hospitals were assessed within 7 days after birth. RESULTS: The birth prevalence rates of cleft lip (CL) and of cleft lip with cleft palate (CLP) were 5.03/10,000, 8.97/10,000 respectively, then the rate of CL +/- P was 14.0/10,000. The prevalence rates in urban and rural area, in male and female births were 13.28/10,000 and 15.57/10,000, 16.06/10,000 and 11.40/10,000 respectively. Significant difference was found among maternal-age-specific prevalence rates, and the highest one was observed in >or= 35 maternal age group. 87.25% of CL +/- P was isolated forms. No secular trend was found during that period. The perinatal fatality rate of CL +/- P was 19.04%, and the rate in isolated forms was 12.69%, but the rate in syndromic CL +/- P was as high as 62.60%. CONCLUSIONS: No decline trend in prevalence rate of CL +/- P was observed during 1996 approximately 2000. Compared with prevalence rates of CL +/- P in some foreign countries, it was higher in China during same period.

Adult↗

Characteristics of preterm delivery and low birthweight among 113,994 infants in Alberta: 1994-1996.

This study examined the impact of infant and maternal factors on preterm delivery and low birthweight (LBW) in Alberta between January 1, 1994 and December 31, 1996. Data on 113,994 births were collected from vital statistics registration birth data. Logistic regression models for preterm and LBW delivery suggested the key risk factors were multiple and still birth (odds ratios > 22.0). Other characteristics included female gender, birth defects, nulliparous women, maternal age 35 and greater, unmarried, history of abortion, maternal smoking, maternal street drug use, and having less than 4 prenatal visits (odds ratios 0.86-2.54). Interactions between smoking and alcohol, and smoking and parity were noted. Efforts to improve the currently low rates (8.2%) of smoking cessation during pregnancy are required. Social, economic and medical factors associated with delayed childbearing and birth outcomes should be investigated.

Adolescent↗

Risk factors for gestational impaired glucose tolerance in the Maltese population: a cross-sectional study.

Screening criteria for impaired carbohydrate metabolism problems during pregnancy include the use of specified risk factors, which are generally considered to be inadequate. The value of these risk factors in a population characterised by a high prevalence of abnormal carbohydrate metabolism is investigated. The study identified biological characteristics such as a maternal age >35 years, previous early pregnancy loss, a maternal family history of DM/IGT, pre-prandial glucosuria and an operative delivery with resuscitation as significant risk factors for the development of G-IGT. There appeared to be no statistical association with a history of multiparity, previous perinatal loss, congenital anomalies or macrosomia and a parental and grandparent family history of DM/IGT. There appeared to be a statistical difference in fasting blood glucose values, but no difference in glycosated haemoglobin. The risk factors for the development of G-IGT are shown to have a high specificity and negative predictive value, but overall moderate to low sensitivity and positive predictive values when used in isolation. The prevalence of the various identified risk factors was very high, a feature which would require at least a third of the population to be screened with an oral glucose tolerance test. These features suggest that the historical and clinical risk criteria are not ideal screening tools to identify G-IGT and a routine early third-trimester oral glucose tolerance test remains the ideal screening tool to identify these cases.

Journal Article↗

Detection and false-positive rates of maternal serum markers for Down syndrome screening according to maternal age in women over 35 years of age. A study of the agreement of eight dedicated software packages.

Maternal serum markers for trisomy 21 screening (MSS) can be assayed in women > or =35 years in an attempt to reduce the need for invasive procedures and thereby avoid their side effects. Our objective was to compare, in women > or =35, eight different software packages dedicated to second trimester MSS, thus providing reliable data for patient counselling. A simulation study was carried out on 189 sera from women with Down syndrome fetuses and 11 962 sera from mothers of unaffected babies. The first step was to estimate the joint distribution of alpha-fetoprotein (AFP) and free beta-human chorionic gonadotrophin (beta-hCG). The second step was to calculate trisomy 21 detection and false-positive rates for each software according to maternal age (35-45 years), using the usual 1:250 risk threshold. Agreement between software packages was measured using 2 x 2 kappa coefficients. Detection rates and false-positive rates increased with maternal age. Depending on the software, 57-71% detection rates were achieved at 35 years with 12-18% false-positive rates. At 45 years, 61-100% detection rates were achieved with 66-95% false-positive rates. Up to 39 years, all softwares were concordant (kappa coefficients >0.75). In the range 35-45 years, false-positive and detection rates increased substantially with maternal age and differences between software packages are observed.

Adult↗

Spontaneous abortion-related deaths among women in the United States--1981-1991.

OBJECTIVE: To examine trends in spontaneous abortion-related mortality and risk factors for these deaths from 1981 through 1991. METHODS: We used national data from the Centers for Disease Control and Prevention's Pregnancy Mortality Surveillance System to identify deaths due to spontaneous abortion (less than 20 weeks' gestation). Case-fatality rates were defined as the number of spontaneous abortion-related deaths per 100,000 spontaneous abortions. We calculated annual case-fatality rates as well as risk ratios by maternal age, race, and gestational age. RESULTS: During 1981-1991, a total of 62 spontaneous abortion-related deaths were reported to the Pregnancy Mortality Surveillance System. The overall case fatality rate was 0.7 per 100,000 spontaneous abortions. Maternal age 35 years and older (risk ratio [RR] 1.7, 95% confidence interval [CI] 0.9-3.0), maternal race other than white (RR 3.8, 95% CI 2.2-5.9), and gestational age over 12 weeks (RR 8.0, 95% CI 4.2-11.9) were risk factors for death due to spontaneous abortion. Of the 62 deaths, 59% were caused by infection, 18% by hemorrhage, 13% by embolism, 5% from complications of anesthesia, and 5% by other causes. Disseminated intravascular coagulation (DIC) was an associated condition among half of those deaths for which it was not the primary cause of death. CONCLUSION: Women 35 years of age and older, of races other than white, and in the second trimester of pregnancy age are at increased risk of death from spontaneous abortion. In addition, DIC complicates many spontaneous abortion cases that end in death. Because spontaneous abortion is a common outcome of pregnancy, continued monitoring of spontaneous abortion-related deaths is recommended.

Abortion, Spontaneous↗