Why semen is cleaned of abnormal sperms

Semen in a test-tube set for analysis. [iStockphoto]

In Vitro Fertilization (IVF) is a technology in which an egg (from a woman) is fertilized outside the human body (with sperms from a man), in a lab setting.

"The fertilized egg is then transferred into the womb of the woman where it should implant and develop into a pregnancy," explains Dr Kireki Omanwa, a fertility expert.

Dr Omanwa, also the President of Kenya Obstetrical and Gynaecological Society (KOGS), says before a woman is put on IVF, they require a first consultation which is intense and tedious to extract as much info as possible. Counselling may come into play as IVF is the only hope of conceiving.

Dr George Ogweno, an IVF specialist in Nairobi says after consultation, tests and screening including blood tests, hormonal tests and fertility evaluation follows. A male partner, on the other hand, undergoes sperm tests.

"Once treatment starts, serial hormonal checks and ultrasounds are done periodically," explained Dr Ogweno.

Here is what happens thereafter:

• IVF starts on Day 1 or 2 of a woman's menses. A blood test to check hormone levels is done. A scan checks if the ovaries are healthy.

If okayed, the daily injections of a hormone called FSH - to stimulate the ovary to start maturing the eggs, starts. The injections happen daily at specific times for between 10 and 14 days.

• As the injections continue, regular scans monitor how follicles are responding to injections to gauge whether dosage needs increasing or not.
• After 10-14 days of daily injections, a last scan to gauge maturity of follicles (between 18 and 20 ml in diameter) is done.

A trigger injection - which finally matures the egg - is given and after 36 hours, eggs are aspirated through the vagina using a special needle in the theatre. The harvest is given to an embryologist while the male partner provides semen sample.

• The semen sample is cleaned of abnormal sperms and the best sperms picked, its tail cut and the head injected into one egg. The fertilised egg is put in a warm place (at 37.2).
• The embryo starts growing from one cell to eight and so on. After three days, the embryologists checks for successfully developed embryos-of which a maximum of three are then transferred into the woman's womb (or a surrogate) using ultrasound. At least one embryo is expected to implant.
• The patient is then put on progesterone - the hormone that sustains the pregnancy - either through injections, swallow-able tablets or medication through the vagina.

In natural setting, the follicle that gives the egg collapses into a corpus luteum - which naturally produces progesterone.

But in IVF, the follicles are punctured during egg harvesting, hence the need for progesterone injections. Progesterone is given until the pregnancy reaches 13 weeks; after which it is left to naturally progress.