Maternal age

A total of 448 of the 500 pregnancies were monitored for cytogenetic Indications exclusive of fetal sex. Of these, 332 were for advanced maternal age, with 172 of that group being between 35 and 39 years of age and 160 being 40 years or over ... 

The mean maternal age for the 12 mothers included in this study was 25.8 years, with a range of 20 to 31 years. Mother s race was 75 percent black, 17 percent white, and 8 percent Hispanic. All were low income. Eighty-three percent of the women were multiparas with an average of 5.2 previous pregnancies and 2.7 live births. 

T3. Thompson, M. W., Heredity, maternal age, and birth order in etiology of celiac disease. Am. J. Human Genet. 3, 159 (1951). 

Clinical Coirelate Maternal Age, Risk of Down Syndrome, and Prenatal Dia wsis... 

The increased risk of trisomy with advanced maternal age motivates more than half of pregnant women in North America to undergo prenatal diagnosis (most commonly, amniocentesis or chorionic villus sampling, discussed in Oiapter 6). Down syndrome can also be screened by assaying maternal serum levels of a-fetoprotein, chorionic gonadotropin, and unconjugated estriol. This so-called triple screen can detect approximately 70% of fetuses with Down syndrome. 

Although there is conclusive evidence for an increased risk of Down syndrome with advanced maternal age, there is little or no evidence for a paternal age effect on Down syndrome risk (choice B),... 

Figure 5. Correlation of maternal age with incidence of human diseases caused by chromosome abnormalities (redrawn from Ref. 5)...

Figure 4.9 Maternal age and the production of Down syndrome offspring. (Redrawn from Penrose and Smith, 1966.)...

In Sweden, analysis of birth registries showed that the population of subfertile women (defined as those who did not become pregnant after more than 1 year) actually decreased from 12.7% in 1983 to 8.3% in 1993 in the general population ( et al., 1999a). The decrease, which was independent of maternal age, was considered linked to a decrease of sexually transmitted disease incidence in Sweden. 

Biotinidase activity can be measured in cultured amniotic fluid cells and in amniotic fluid. Therefore, prenatal diagnosis of biotinidase deficiency is possible. Prenatal diagnosis has been performed in two at-risk pregnancies in which amniocentesis was performed because of advanced maternal age. The fetuses were found to be unaffected, and this was confirmed after birth. In addition to enzyme determination in amniocytes, a fetus was correctly shown to be a heterozygote by molecular mutation analysis in an at-risk pregnancy. Because treatment is so effective in this disorder, some laboratories are now performing prenatal diagnosis. 

V6. Virro, M. R., and Shewchuk, A. B., Pregnancy outcome in 242 conceptions after artificial insemination with donor sperm and effects of maternal age on the prognosis for successful pregnancy. Am. J. Obstet. Gynecol. 148, 518-524 (1984). 

The auditory brainstem responses (ABR) in neonates who were exposed prenatally to cocaine showed prolonged absolute peak latencies compared with non-exposed neonates and may indicate compromise of the auditory system from gestational exposure to cocaine (333). Among 58 infants studied, 21 (36%) were positive by meconium analysis for cocaine, and five (8.5%) were also positive for cannabinoids. There were significant differences in mean maternal age, gravidity, parity, birth weight, and head circumference among cocaine-exposed infants. 

Spermicide use for more than a year at any time before conception was more common in cases aborting a trisomic conception than in controls. The association varied with maternal age, and was confined to women aged 30 years or older (13). However, it has since been concluded that there is no convincing evidence of an increased risk of fetal abnormalities in women who become pregnant while using spermicides, or in women who have used them before realizing that they were pregnant (14). 

An excess number of autosomes or the absence of one or more autosomes can either be lethal to the embryo or result in well-known conditions. For example, the risk of Down s syndrome (trisomy 21 or mongolism) increases with maternal age - being one in 2000 for mothers aged 40 or more years. Extra chromosomes 17 and 18 result in micro- or anophthalmia (congenital absence of the eyeball), mental retardation, cleft lip, cleft palate, and deafness this condition occurs on average once in every 5000 births. 

Figure 54-4 The relationship of maternal age and the risk of having a pregnancy affected with Down syndrome. Dotted line, Second trimester risk so/id line, term risk. Vertical line at age 35 is the cutoff used for selecting women at increased risk based on maternal age.

The detection and false-positive rates achievable depend on many factors includmg (1) the test combination chosen, (2) the risk cutoff chosen, (3) the method of dating used to establish gestational age, and (4) the maternal ages of the women being tested. Table 54-3 summarizes the impact of these factors in a hypothetical cohort of women having the maternal age distribution found in the United States in 2000. In the United States, many laboratories use the triple test (AFP, uEj, CG) and a cutoff equivalent to the risk of a 35-year-old woman (1 270 in the second trimester or 1 350 at term). At this risk cutoff and with use of the date of the... 

Second Trimester Maternal Age and Risk Cutoff (term) Serum Markers DR (%) FPR (%) OAPR(l n) ... 

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