What every patient needs to know about their sperm, eggs and embryos
Dr Sai , Embryologist, Malpani Infertility Clinic
Embryologists are the scientists who make your embryos from your eggs and sperms in the IVF lab. In many clinics, the embryologists are tucked away in the IVF lab, which is why most infertile couples don’t have a clue as to what we do and how we do it.
At Malpani Infertility Clinic, I routinely show our patients their embryos in the IVF lab. It’s much easier for them to understand what we do in the IVF Lab when they know the basic biology of sperm, eggs and embryos.
Here’s a basic Reproductive Biology 101 course you should review before going in for IVF treatment.
There are two type of gametes- sperm and eggs.
Sperms (Male Reproductive Cells) :
 
- A Sperm has a tail which helps it move and an oval shaped head to penetrate an egg in order to fertilise it.
- The normal human testes produces millions of sperms. But to fertilise an egg , only one sperm is required.
- Qualitatively sperms would be Good , Bad and Ugly.
- A semen sample is mainly screened in an Andrology Lab for the following parameters:
Sperm Count : >= 20 mill./ml [ Normal parameter according to WHO ]
Total Motility : > 50 % [ Normal parameter according to WHO ]
Grade IV : Rapidly progressive motility : 25 % of total Motility
Grade III : Moderately progressive motility
Garde II : Sluggish motility
Total Abnormal Sperms : < 30% [ Normal parameter according to WHO ]
Semen Samples with certain deficiencies are termed as follows :
Oligospermia : Semen samples with sperm count lesser than Normal values (< 20 mill./ml.)
Asthenospermia : semen samples with total motility lesser than Normal values(< 50%)
Teratospermia : semen samples with total abnormal sperms more than Normal values ( > 30%) Abnormal sperm samples will often have combinations of above conditions.
Azoospermia : Semen samples with no sperms at all. This may be due to obstruction or
testicular failure.
Egg (Female Reproductive Cell):
 
In a normal menstrual cycle, a woman produces one egg in either ovary.- Ovulation is the time when this mature egg is released into the fallopian tube
- The ovulation occurs only if the egg matures.
- Once the egg ovulates, it goes in to fallopian tubes, where it waits for the sperms to fertilise it.
- A human egg is about 100 microns in size – which makes it the largest cell in the body. If it is not fertilized within 24 hours of its ejection from the ovary, it dies.
How does fertilization occur?
Fertilization occurs when a live sperm penetrates the newly released mature egg successfully and cell division starts.
  
The successful sperm fuses with the egg. This is called fertilization and the fertilized egg is now called a “zygote” or embryo.
The Fertilised egg will develop further as follows:
The Cell divides into 2
Will further divide into 4-Cells
4-Cells will further divide into 6-Cells
Division continues
All Cells fuse together and get compacted
The Embryo will hatch (come out of its shell, called the zona)
This hatched blastocyst will finally implant in the uterus. |
ASSISTED REPRODUCTIVE TECHNIQUES- ART allow us to achieve fertilization outside the human body.
Superovulation
The ovaries are stimulated to produce many follicles. The eggs are retrieved by egg collection.
These retrieved eggs are then fertilized in the IVF lab by IVF or ICSI.
IVF:
This is a simple technique of achieving fertilization : - The wife’s eggs and partner’s sperms (washed sperms) are kept together in a culture dish in an incubator, allowing the sperm to penetrate into the egg and fertilise them
- The eggs are then checked next day for presence of 2 pronuclei to confirm fertilization.
- They are allowed to divide further and the best embryos are transferred into wife’s uterus.
Limitations of Conventional-IVF : In IVF, to fertilise one single egg, we require 100,000 normal, rapidly motile sperms. If the man does not have enough sperm, we can use ICSI. ICSI (Intracytoplasmic Sperm Injection): - ICSI is an advanced assisted fertilization technique.
- Fertilization is achieved by injecting one single sperm into each egg.
- To perform ICSI, we require a special instrument called a micromanipulator.
- This allows us to handle the microscopic eggs and sperms.
- All injected eggs are incubated and checked the next day for presence of pronuclei, to confirm fertilization.
- They are allowed to divide further and the best embryos are transferred into wife’s uterus.
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