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Sex chromosomal abnormalities. Etiology, phenotypic expression, and the role of lyonization.

Individuals with sex chromosomal abnormalities have significantly better chances of leading normal lives than individuals with autosomal abnormalities. This is due, in part, to the role of lyonization in the genetic inactivation of X chromosomes. In contrast to earlier studies contaminated with subject ascertainment bias, prospective studies of individuals with SCA generally indicate a relatively normal profile with respect to overall intellectual capacity and psychopathology. Although some SCAs affect neuromotor, speech, language, cognitive and emotional development to some degree, it is noteworthy that none of the effects necessarily occurs and that some of the deficits are amenable to corrective intervention. Results from prospective studies also indicate significant genotype-environment interactions that can have important implications for intervention.

Dosage Compensation, Genetic↗

Causes of chromosome anomalies suggested by cytogenetic epidemiology of induced abortions.

Women who visited hospitals requesting induced abortions were asked about their obstetric and medical histories by attending physicians prior to the operation. The information was solely based on their reports at the interview. The period of coverage was nine weeks, comprising six weeks before and three weeks after the onset of the last menstruation. Both the occurrence of acute respiratory infectious diseases, which included the common cold, upper respiratory tract infection (U.R.T.I.), influenza, and pneumonia, and the use of analgesics and antipyretics were most frequently reported. Regardless of whether they had an acute respiratory illness, the women who took analgesics and antipyretics (including antihistamine, cough remedy, and nasal decongestant) had 13.8% (8/58) gross chromosome anomalies. The women without the treatment had 6.3% (71/1136) anomalies. The difference was statistically significant (P less than 0.05). Triploid formation was particularly related to drug consumption, thus there were 5.2% (3/58) in the treated group and 0.5% (6/1136) in the untreated group (P=0.0074). In contrast, trisomy was not considered to be related to drug consumption on account of 8.6% (5/58) and 4.1% (47/1136) in the corresponding groups (0.10 less than P less than 0.20). When the occurrence of trisomy was examined in connection with two variables, i.e., the presence of drug consumption and the age of mothers, association was not evident (X2 assoc. = 0.883, d.f. = 1 by Cochran's method). Besides these results, neither maternal X-irradiation nor irregularity of the menstrual period was found to be related to the frequency of chromosome anomalies in the progeny.

Abortion, Induced↗

Aged gametes, adverse pregnancy outcomes and natural family planning. An epidemiologic review.

Unconfirmed epidemiologic studies suggest a possible increased risk of birth defects associated with Natural Family Planning (NFP) use, and an increased incidence of spontaneous abortion or frequency of chromosomal abnormalities in abortuses associated with conceptions outside the most "fertile period". The risk is approximately two- to four-fold, but the evidence is by no means conclusive. The implication for NFP depends on the frequency of method failures in user populations, but is not likely to constitute a major hazard. Further research could utilize a data bank of NFP charts.

Abortion, Spontaneous↗

Oral contraception and congenital abnormalities.

Of 10 479 single births in South Glamorgan between January 1974 and June 1976, 27.3 per cent of infants were born to women who had used oral contraception in the three months prior to their last menstrual period (users) and 72.3 per cent were born to women who had not used oral contraception during the same period (non users). There were significantly more infants with neural tube defects among users compared with non users. Abnormalities of the digestive, genito-urinary and cardiovascular system, bones, muscle, skin and connective tissues, endocrine glands, blood chromosomes and oral clefts, were of similar incidence in the two groups.

Abnormalities, Drug-Induced↗

Lack of association between spermicide use and trisomy.

It has been suggested that the maternal use of spermicidal contraceptives increases the frequency of certain congenital anomalies, including trisomy, but this issue is in dispute. This controversy led us to examine whether the use of spermicidal contraceptives is associated with an increased risk of fetal trisomy. A questionnaire concerning contraceptive use was completed by 13,729 women who were undergoing prenatal fetal chromosome studies but were as yet unaware of the results. Most women were at increased risk of having a trisomic fetus because of their advanced age. Of 154 fetuses with trisomy, 98 had trisomy 21. For each woman (case) with an affected fetus, four controls were selected from among women with chromosomally normal fetuses, matched for maternal age and medical center. Cases and controls were compared by matched-sample maximum-likelihood logistic regression, to examine the association between fetal trisomy and four measures of spermicide use: periconceptional use, timing of last use, duration of last use, and total lifetime use. No evidence was found for an association, either when all types of trisomy were combined or when trisomy 21 alone was considered. All point estimates of odds ratios relating spermicidal exposure to trisomy were approximately 1, and an effect greater than a twofold increase was excluded with 95 percent confidence in the combined-trisomy group for all measures of spermicide use.

Down Syndrome↗

Fetal anatomical abnormalities and other associated factors in middle-trimester abortion and their relevance to patient counselling.

Fetuses present in 91 consecutive spontaneous or missed middle-trimester abortions were studied anatomically and tissue karyotyping was attempted. Anatomical abnormalities were found in 32 fetuses, two of these also had chromosomal abnormalities, six of these abortions were associated with other possible aetiological factors. In a further 23 pregnancies there were probably significant aetiological factors associated with the abortion and in 10, where the fetus had arrested growth, there were two with other possible factors. From a prospective analysis of subsequent pregnancies it would appear that if all the factors relating to middle-trimester abortion, including fetal autopsy, are analysed, better patient counselling and realistic prognoses can be given for subsequent pregnancy.

Abortion, Spontaneous↗