Secondary infertility (SI) is defined by doctors as the inability to conceive or carry to term a second or subsequent child. You may not have heard of it but you probably soon will, because it's on the increase. A US study revealed that, in 1995, 1.8 million women suffered from secondary infertility; in 2006, it was 3.3 million. SI now accounts for six out of 10 infertility cases.

In egg donation and embryo donation, the resultant embryo after fertilisation is inserted in another woman than the one providing the eggs. These are resources for women with no eggs due to surgery, chemotherapy, or genetic causes; or with poor egg quality, previously unsuccessful IVF cycles or advanced maternal age. In the egg donor process, eggs are retrieved from a donor's ovaries, fertilised in the laboratory with the sperm from the recipient's partner, and the resulting healthy embryos are returned to the recipient's uterus.
Obesity: The obesity epidemic has recently become is a serious issue, particularly in industrialized nations. The rising number of obese individuals may be due in part to an energy-rich diet as well as insufficient physical exercise.  In addition to other potential health risks, obesity can have a significant impact on male and female fertility. BMI (body mass index) may be a significant factor in fertility, as an increase in BMI in the male by as little as three units can be associated with infertility. Several studies have demonstrated that an increase in BMI is correlated with a decrease in sperm concentration, a decrease in motility and an increase DNA damage in sperm. A relationship also exists between obesity and erectile dysfunction (ED). ED may be the consequence of the conversion of androgens to estradiol. The enzyme aromatase is responsible for this conversion, and is found primarily in adipose tissue. As the amount of adipose tissue increases, there is more aromatase available to convert androgens, and serum estradiol levels increase. Other hormones including inhibin B and leptin, may also be affected by obesity. Inhibin B levels have been reported to decrease with increasing weight, which results in decreased Sertoli cells and sperm production. Leptin is a hormone associated with numerous effects including appetite control, inflammation, and decreased insulin secretion, according to many studies. Obese women have a higher rate of recurrent, early miscarriage compared to non-obese women.

Any embryos that you do not use in your first IVF attempt can be frozen for later use. This will save you money if you undergo IVF a second or third time. If you do not want your leftover embryos, you may donate them to another infertile couple, or you and your partner can ask the clinic to destroy the embryos. Both you and your partner must agree before the clinic will destroy or donate your embryos.
Gathering the eggs. Your doctor gives you an anesthetic and inserts an ultrasound probe through your vagina to look at your ovaries and identify the follicles. A thin needle is then inserted through the vaginal wall to remove the eggs from the follicles. Eight to 15 eggs are usually retrieved. You may have some cramping and spotting for a few days afterward, but most women feel better in a day or two.
Alana Stewart, who was conceived using donor sperm, began an online forum for donor children called AnonymousUS in 2010. The forum welcomes the viewpoints of anyone involved in the IVF process.[121] Olivia Pratten, a donor-conceived Canadian, sued the province of British Columbia for access to records on her donor father's identity in 2008.[122] "I'm not a treatment, I'm a person, and those records belong to me," Pratten said.[119] In May 2012, a court ruled in Pratten's favour, agreeing that the laws at the time discriminated against donor children and making anonymous sperm and egg donation in British Columbia illegal.[122]
Intercourse must take place frequently, particularly before and around the time of ovulation, and the couple must have been trying to conceive for at least one year (6 months if the woman is over 35 years old). Using these criteria, about 10-20% of all infertile couples have unexplained infertility. However, the percentage of couples classified as having unexplained infertility will depend upon the thoroughness of testing and the sophistication of medical technology. 
3-6 months of treatment with Clomid pills (clomiphene citrate) might improve fertility by as much as 2 times as compared to no treatment. This is a very low level infertility treatment. Infertility specialists do not usually recommend Clomid treatment( without insemination) for unexplained infertility for women over the age of about 35. Most fertility specialists do not use it (without IUI) on any couples with unexplained infertility. If a woman is already having regular periods and ovulating one egg every month, giving Clomid, which will probably stimulate the ovaries to release 2 or 3 eggs per month (instead of one) is not really fixing anything that is broken - and is not likely to be successful.