Genetic factors in assisted reproduction

Paternal age and congenital malformations

BACKGROUND

Spontaneous mutations in germ cells increase with male age, but an association between paternal age and congenital malformations is not well established. We conducted a population-based cohort study to estimate this association.

METHODS

A study population of couples and their firstborn children were identified in the Danish Fertility Database between 1980 and 1996 (n = 71937). Diagnoses of congenital malformations in children were obtained by linkage to the nationwide hospital register (1980-1999).

RESULTS

Overall, there were no differences in the prevalence of malformations as a function of paternal age. However, the prevalence of malformations of extremities and syndromes of multiple systems, as well as Down's syndrome, increased with increasing paternal age. For example, in comparison with fathers age 20-29 years, adjusted hazard ratio of syndromes of multiple systems was 1.15 [95% confidence interval (CI) 0.81-1.65] for age 35-39 years, 1.33 (95% CI 0.79-2.25) for age 40-44 years, 1.73 (95% CI 0.82-3.65) for age 45-49 years, and 3.20 (95% CI 1.37-7.48) for age > or = 50 years (test for trend P = 0.01).

CONCLUSIONS

Our data suggest that advanced paternal age may be associated with an excess occurrence of some specific malformations. The association could be caused by mutations of the gametes in men induced by biological or environmental factors.

Prevalence of chromosome defects in azoospermic and oligoastheno-teratozoospermic South Indian infertile men attending an infertility clinic

The prevalence of chromosomal abnormalities in azoospermic and oligoastheno-teratozoospermic infertile men of South Indian origin undergoing assisted reproductive technologies was evaluated. In addition, the study aimed to investigate new abnormal karyotypes involving autosomes in azoospermia and sex chromosomes in oligoastheno-teratozoospermic individuals that are supposed to be rare. Metaphase chromosomes of 744 infertile men, including 272 men with azoospermia and 472 men with oligoastheno-teratozoospermia (OAT), were analysed using Giemsa-trypsin-Giemsa banding and fluorescence in-situ hybridization (FISH) wherever necessary. Chromosomal abnormalities were observed in 59 (7.9%) individuals of the total studied population. Among these, 30 out of 272 (11.0%) azoospermic men and 29 out of 472 (6.1%) infertile men with OAT showed chromosomal abnormalities. A strong and statistically significant association (OR = 1.89; P = 0.0235) of chromosomal abnormalities and sex chromosome abnormalities (OR = 4.29; P = 0.001) with azoospermia when compared with OAT was observed. In addition, six autosomal abnormalities associated with azoospermia and two abnormalities involving Y chromosome, which include a novel karyotype (mos 46,XY/51,XYYYYYY) in OAT individuals, were detected.