The main durations of embryo culture are until cleavage stage (day two to four after co-incubation) or the blastocyst stage (day five or six after co-incubation).[71] Embryo culture until the blastocyst stage confers a significant increase in live birth rate per embryo transfer, but also confers a decreased number of embryos available for transfer and embryo cryopreservation, so the cumulative clinical pregnancy rates are increased with cleavage stage transfer.[30] Transfer day two instead of day three after fertilisation has no differences in live birth rate.[30] There are significantly higher odds of preterm birth (odds ratio 1.3) and congenital anomalies (odds ratio 1.3) among births having from embryos cultured until the blastocyst stage compared with cleavage stage.[71]

Psychological factors: Studies on infertile groups of men and women have produced contradictory findings of the importance of psychological factors in causing infertility. Emotional disturbances undoubtedly appear to have some significance. This is only reasonable if you realize that the whole hormonal cycle, with its delicate adjustments, is controlled from the brain. This is an area which needs further investigation.

Heavy, as in a pad and a tampon still doesn’t feel like enough. Certain medical conditions, like thyroid problems or kidney disease, can cause excessive menstrual bleeding, medications (such as anti-inflammatory drugs or anti-coagulants) may as well; or the reason may be a condition linked to infertility. In a normal menstrual cycle, the hormones estrogen and progesterone work together to regulate the buildup of the lining of the uterus—that’s the stuff that sheds during your period. But if, for example, your ovaries don’t release an egg, the dominoes are tipped: your body produces less progesterone, hormones become imbalanced, the lining in your uterus over-develops, and you end up bleeding extra heavily. Fibroids in your uterus can also cause heavier or longer-than-normal periods; some types of these benign tumors can block fallopian tubes or interfere with the implantation of a fertilized egg. Up to 10 percent of infertile women have fibroids, according to the American Society for Reproductive Medicine. If you soak through at least one pad or tampon an hour for more than a few hours, see your doctor.  This is the worst health advice gynecologists have ever heard.
In IUI, this natural sequence of events is given some assistance. A sample of sperm is prepared in the laboratory so that only the best moving sperm are concentrated together. This sperm is then deposited directly into the uterus without having to swim there on its own, which can be challenging, especially if the sperm do not swim well. IUI places a higher concentration of moving sperm closer to the ovulated egg. Often a woman will have taken medication prior to the IUI procedure to ensure she will ovulate around the time of the procedure, so egg and sperm can meet.
Repeated failed rounds of IVF can help identify causes of infertility. For example, if sperm and egg quality are normal, then the conception issue may be rooted at the embryonic or implantation level. In other words, if IVF fails to result in pregnancy despite successful fertilization, embryonic development or implantation may be to blame. Still this is a very expensive way to start getting answers.