Implantation in patients over 40 and raising FSH levels--a review.

There is an evident decline of female fertility with age. This decline is mainly due to increased risk of pregnancy termination either after conception or after embryo implantation. Very likely the major cause of this embryo and pregnancy loss is chromosomal aneuploidies caused mostly by increasing rates of 'poor quality' oocytes. This phenomenon can be explained either by an age dependent accumulation of damage and/or by the hypothesis that the defective oocytes are there in the ovaries from the fetal life. 'Good quality' oocytes are ovulated first, leaving 'poor quality' oocytes to be ovulated later in life. Besides the quality of the oocytes which is mainly responsible of the embryo quality (we have not to forget a paternal effect) the process of implantation is dependent upon two variables: the probability of a viable embryo and that of a receptive uterine environment. From the oocyte donation model it seems that the endometrium also plays a minor role in human reproductive ageing as it does in some laboratory animals. However, besides some macroscopic possible causes which may play a role in the reduction of the age-related endometrial receptivity, there are so many endometrial factors possibly related to its receptivity which need to be further studied especially in older women.