OBJECTIVE: To clarify the prenatal sex ratio, and types and frequencies of chromosome anomalies in relation to gestational weeks in women of advanced maternal age. METHODS: Chromosomal analysis was performed in 894 induced abortuses derived from elderly pregnant women 35 or more years of age. RESULTS: The embryonic sex ratio in the chromosomally normal (abnormal) gave a preponderance of females over males in lower gestational weeks [366/458 (63/73); 79.9 to 100 (86.3 to 100) in 4-10 weeks]; the reversal of dominancy in those from females to males occurred in the 11th gestational week [41/29(5/4); 141.4 to 100 (125.0 to 100) in 11-20 weeks]. The frequency of trisomy in females at 10 weeks of gestation was significantly high (7/28; 25%). CONCLUSIONS: This study showed that the existence of a difference of and a reversal of the sex ratio in gestational weeks. It was considered that there might be a lower viability of genetically handicapped males as compared to such females. However, the reversal of the sex ratio, such as that observed between 9th and 10th gestational weeks, might reflect events occurring after implantation.
OBJECTIVE: To clarify the prenatal sex ratio, and types and frequencies of chromosome anomalies in relation to gestational weeks in women of advanced maternal age. METHODS: Chromosomal analysis was performed in 894 induced abortuses derived from elderly pregnant women 35 or more years of age. RESULTS: The embryonic sex ratio in the chromosomally normal (abnormal) gave a preponderance of females over males in lower gestational weeks [366/458 (63/73); 79.9 to 100 (86.3 to 100) in 4-10 weeks]; the reversal of dominancy in those from females to males occurred in the 11th gestational week [41/29(5/4); 141.4 to 100 (125.0 to 100) in 11-20 weeks]. The frequency of trisomy in females at 10 weeks of gestation was significantly high (7/28; 25%). CONCLUSIONS: This study showed that the existence of a difference of and a reversal of the sex ratio in gestational weeks. It was considered that there might be a lower viability of genetically handicapped males as compared to such females. However, the reversal of the sex ratio, such as that observed between 9th and 10th gestational weeks, might reflect events occurring after implantation.
Authors: Steven Hecht Orzack; J William Stubblefield; Viatcheslav R Akmaev; Pere Colls; Santiago Munné; Thomas Scholl; David Steinsaltz; James E Zuckerman Journal: Proc Natl Acad Sci U S A Date: 2015-03-30 Impact factor: 11.205