Lack of correlation between contraceptive pills and Down's syndrome

Ovulation suppression protects against chromosomal abnormalities in mouse eggs at advanced maternal age

The frequency of egg aneuploidy and trisomic pregnancies increases with maternal age. To what extent individual approaches can delay the "maternal age effect" is unclear because multiple causes contribute to chromosomal abnormalities in mammalian eggs. We propose that ovulation frequency determines the physiological aging of oocytes, a key aspect of which is the ability to accurately segregate chromosomes and produce euploid eggs. To test this hypothesis, ovulations were reduced using successive pregnancies, hormonal contraception, and a pre-pubertal knockout mouse model, and the effects on chromosome segregation and egg ploidy were examined. We show that each intervention reduces chromosomal abnormalities in eggs of aged mice, suggesting that ovulation reduction delays oocyte aging. The protective effect can be partly explained by retention of chromosomal Rec8-cohesin that maintains sister chromatid cohesion in meiosis. In addition, single-nucleus Hi-C (snHi-C) revealed deterioration in the 3D chromatin structure including an increase in extruded loop sizes in long-lived oocytes. Artificial cleavage of Rec8 is sufficient to increase extruded loop sizes, suggesting that cohesin complexes maintaining cohesion restrict loop extrusion. These findings suggest that ovulation suppression protects against Rec8 loss, thereby maintaining both sister chromatid cohesion and 3D chromatin structure and promoting production of euploid eggs. We conclude that the maternal age effect can be delayed in mice. An implication of this work is that long-term ovulation-suppressing conditions can potentially reduce the risk of aneuploid pregnancies at advanced maternal age.

Epidemiology of Down syndrome: new insight into the multidimensional interactions among genetic and environmental risk factors in the oocyte

Down syndrome birth is attributable to multiple maternal risk factors that include both genetic and environmental challenges, but there is limited understanding of the complicated interactions among these factors. In the present study, a case-control analysis of approximately 400 infants with or without suspected Down syndrome reported between 2003 and 2009 and their parents in and around Kolkata, India, was conducted. Maternal exposure to 2 environmental risk factors (smokeless chewing tobacco and oral contraceptive pills) was recorded, and families were genotyped with microsatellite markers to establish the origin of nondisjunction errors as well as recombination patterns of nondisjoined chromosome 21. With logistic regression models, the possible interactions among all of these risk factors, as well as with maternal age, were explored. Smokeless chewing tobacco was associated with significant risk for meiosis II nondisjunction and achiasmate (nonexchange) meiosis I error among young mothers. By contrast, the risk due to oral contraceptive pills was associated with older mothers. Study results suggest that the chewing tobacco risk factor operates independently of the maternal age effect, whereas contraceptive pill-related risk may interact with or exacerbate age-related risk. Moreover, both risk factors, when present together, exhibited a strong age-dependent effect.

Recent oral contraceptive use and adverse birth outcomes

OBJECTIVE

To examine the possible association between oral contraceptive use and adverse birth outcomes.

STUDY DESIGN

We conducted a population-based cohort study of pregnant women who used oral contraceptives within 3 months before their last menstrual period. Subjects were divided into three groups, according to the interval (0-30, 31-60, and 61-90 days) between the dispensing date and their last menstrual period. For each exposed subject, 4 subjects without exposure to oral contraceptives were individually matched by infant's year of birth and plurality and by mother's age and parity.

RESULTS

Oral contraceptive use within 30 days prior to the last menstrual period was associated with increased risks of very low birth weight (OR: 3.24, 95% CI: 1.18, 8.92), low birth weight (OR: 1.93, 95% CI: 1.17, 3.20), and preterm birth (OR: 1.61, 95% CI: 1.01, 2.55); however, oral contraceptive use 31-90 days prior to the last menstrual period did not increase the risk of low birth weight or preterm birth.

CONCLUSION

Our results indicate the use of oral contraceptives near the time of conception may be associated with an increased risk of low birth weight and preterm birth.

Pregnancy outcome after exposure to oral contraceptives during the periconceptional period

To evaluate whether periconceptional exposure to oral contraceptives (OCs) increased adverse pregnancy outcomes, 136 pregnant women taking OCs within the periconceptional period were identified at the Korean Motherisk Program. Of them, 120 pregnant women accepted to participate in their study and were followed up until completion of the pregnancy. A control group of 240 age- and gravidity-matched pregnant women exposed to non-teratogen drugs for at least 1 month before pregnancy was also included. The median gestational age at delivery was 39.1 (27.0-41.0) weeks in the exposed group and 39.3 (27.4-42.0) weeks in the control group (P = 0.19). In the exposed group, 7.1% of babies were born with low birth weight versus 2.6% in the control group (P = 0.068). The number of preterm deliveries or babies born large for gestational age did not differ between the two groups. In the exposed group, the rate of birth defects was 3.2% (n = 3/99) versus 3.6% (n = 7/193) in the control group (P = 1.0). There were 15 women who took high doses of progesterone (emergency contraception) and no adverse fetal outcomes were observed. In conclusion, periconceptional exposure to OCs does not appear to increase the risk for adverse pregnancy outcomes.

Epidemiology of Down syndrome in 118,265 consecutive births

The epidemiology of Down syndrome (DS) was studied in the area which is covered by our registry of congenital malformations. For each of the 139 new DS cases which were ascertained during the period 1979 to 1987 more than 50 factors were studied and compared to those from control infants. The prevalence of DS was 1.17%; 3.6% of the DS cases were stillbirths and 14.4% were induced abortions. Karyotypes were obtained in 137 cases of which all but 7 were 47, + 21, 4 were mosaics (2.8%), and 5 had translocations (3.6%). Interchromosomal effect was a question in 3 cases. The most common types of associated malformations were cardiac anomalies (44.6%) and intestinal atresia. We did not observe seasonality or time/space clusters in spite of the Chernobyl nuclear accident. No paternal age effect was demonstrated. In our material the first-born infants were at lower risk of DS than the later born. Five percent of the mothers of DS had 2 previous spontaneous abortions (controls 2.8%). At birth, the DS infants measured less and their head circumference was lower than in control infants. Weight of placenta was also lower than in control infants. In our material there were 7.9% of consanguineous marriages (P = .010). The pregnancies of the DS children were often complicated by threatened abortions; 6.4% of the mothers of the DS children were diabetic (P = .069). For all other factors studied no statistically significant difference with respect to controls could be demonstrated.

Periconceptional exposure to contraceptive pills and risk for Down syndrome

OBJECTIVE

There are some studies which analyzed the relationship between prenatal exposure to oral contraceptives (OCs) and Down syndrome, with conflicting results even in women using OCs and conceiving at different intervals after discontinuing the use of contraceptive pills. We analyzed the risk for Down syndrome in infants of women who become pregnant while taking OC.

STUDY DESIGN

We used the data from the Spanish Collaborative Study of Congenital Malformations (ECEMC). The ECEMC is a case-control study and surveillance system. For each malformed infant (case), the next non-malformed infant of the same sex born in the same hospital is selected as a control subject, from whom the collaborating physicians collected the same data as for the malformed infant. For the present study, we used two different approaches. First, the pair-matching analysis. Second, a case-control using the rest of the total of 17,183 controls from the ECEMC database with specified data on maternal use of OCs and maternal age. To control for maternal age, we used a logistic regression analysis.

RESULTS

The results show an increased risk of 2.8-fold for infants with Down syndrome in women younger than 35 years of age if the mother became pregnant while she was taking OCs. We did not observe this result for women older than 34 years of age.

CONCLUSION

Our results showed that the risk for Down syndrome in infants born to mothers with less than 35 years of age (as a group) who became pregnant while taking OCs is near the risk for Down syndrome of mothers with more than 34 years of age, women who are candidates for prenatal diagnosis. Thus, based on our results, one may consider the possibility of offering prenatal diagnosis for Down syndrome to young women who became pregnant while taking OCs.

Risk factors for trisomy 21: maternal cigarette smoking and oral contraceptive use in a population-based case-control study

PURPOSE

We examined maternal smoking and oral contraceptive use as possible risk factors in the genesis of cases of trisomy 21 of maternal origin. This is the first epidemiological study to categorize cases of trisomy 21 by parent of origin and timing of the meiotic error before assessing possible risk factors.

METHODS

We used chromosome 21-specific DNA markers to assign origin to each case. Structured interviews were employed to determine maternal smoking and oral contraceptive use around conception.

RESULTS

The odds ratio (OR) for maternal smoking was significantly increased among younger mothers (OR = 2.98; 95% CI = 1.01-8.87), but only in a particular subset of meiotically-derived cases. The combined use of cigarettes and oral contraceptives increased the risk further (OR = 7.62; 95% CI = 1.63-35.6); however, oral contraceptive use alone was not a significant risk factor.

CONCLUSION

Our results indicate that categorizing cases of trisomy 21 by parent and timing of the meiotic error allows more precision in identifying risk factors and may shed light on mechanisms of meiotic nondisjunction.

Maternal use of oral contraceptives and Down syndrome

The date of stopping oral contraceptives (OC) in relation to the last menstrual period was studied in 458 women with Down syndrome infants born in 1983-1986 and compared with the expected distribution estimated from the total population of births for these years, after stratification for year of birth, maternal age, and parity. No deviations were seen for the total group, for women less than 30 or 30+ years old, or for Down syndrome infants with known trisomy 21. This is the third study showing no effect and in contrast to the only study which indicates an association between OC use and the birth of an infant with Down syndrome.

Down's syndrome and maternal cancer. A preliminary study

The possible association between maternal cancer and Down's syndrome was studied in a register-based case-control study of 962 women who had an infant with Down's syndrome born during 1973-1981, and to each two controls, matched for maternal age, parity, and year of delivery. A total of 952 complete triplets was obtained. Among them, 63 Down's syndrome mothers and 79 control mothers were found in a cancer registry for the period 1958-1982 (odds ratio 1.6;95% conf. interval 1.3-2.0). Of these, 14 Down's syndrome mothers and 20 controls had malignant lesions (odds ratio 1.4, 0.9-2.2), and 49 Down's syndrome mothers and 55 controls had cervical cancer in situ (odds ratio 1.8, 1.4-2.3). This risk increase was present both before and after the delivery of the Down's syndrome infant. Various explanations of these findings are discussed and the need for further data is stressed.