The term “fertilization” usually refers to fertilization, which is the first step in the biological process that leads to pregnancy. This happens when a sperm fertilizes an egg.
After fertilization, the egg descends into the uterus and attaches itself to the uterine lining. This is known as implantation. Both fertilization and implantation must occur for someone to become pregnant.
Conception is not a medical term. Some people use it to refer only to conception, while others use it to refer to the overall process of creating a pregnancy. Because of this, scientists tend to use more precise terms.
This article discusses what conception is, when and how it happens, and how it works for those undergoing in vitro fertilization (IVF) or surrogacy.
People usually define fertilization as the moment when a sperm fertilizes an egg. This can happen inside the body or outside the body when people use IVF.
However, conception is not a scientific term. It comes from social and philosophical ideas about when human life begins. Some doctors use this word, but others may prefer “conception”, which is more specific.
Conception does not always lead to pregnancy. A person is technically not pregnant until implantation has occurred. This is the moment when the fertilized egg implants in the lining of a uterus, which occurs approximately 5-6 days after conception.
Not all fertilized eggs make it to this stage. It is estimated that 50% of all fertilized eggs do not implant and leave the body in the same way that unfertilized eggs do – during menstruation.
Fertilization can occur only after ovulation. Ovulation is the point in the menstrual cycle when the ovaries release an egg.
In a regular cycle, ovulation usually occurs about 10-16 days before a person’s next period. However, many have irregular cycles that change in length each month, so the exact day of ovulation often varies.
Fertilization can then take place in several ways:
- Sexual Intercourse: During sex, sperm can enter the vagina. From here it can swim up to the uterus and find its way to the egg. This can take a few days, with healthy sperm surviving in the body for up to 5 days.
- Intrauterine insemination (IUI): It involves a doctor placing sperm through a thin tube into the uterus. A doctor can do this for people trying to conceive through sperm donation or for those who choose surrogacy. Surrogacy is when a person other than the biological parents carries the pregnancy.
- IVF: It involves a doctor taking sperm and eggs from two people and combining them in a laboratory setting. IVF cannot guarantee that conception will occur, but creates the best possible conditions for it to happen.
Conception in IVF is unique as it takes place outside the human body. However, this is still conception.
The process
- a female taking a course of fertility drugs, which causes the ovaries to release more eggs than usual, and at predictable times
- a doctor who removes these eggs from the body after ovulation
- a doctor who fertilizes the eggs with sperm, either from a donor or a partner
- the fertilized eggs grow outside the body for several days until they become embryos
- a doctor who places the embryos in the womb
If at least one embryo implants, pregnancy begins.
With surrogacy, conception can take place inside or outside the surrogate’s body. It may depend on whether the surrogate’s eggs are involved, or whether they receive eggs from someone else.
If they are using their own eggs, a doctor can use IUI to create the conditions for fertilization inside the body. If the surrogate does not use their own eggs, a doctor will use IVF to fertilize eggs outside the body.
Learn more about IVF here.
After fertilization, a fertilized egg – or zygote – may or may not implant. If it does implant, pregnancy has begun.
At this stage, the zygote cells begin to divide, and the zygote becomes an embryo. This is the scientific name for an organism with multiple cells. After 8 weeks, the embryo becomes a fetus.
Learn more about pregnancy here.
How to tell that pregnancy has begun
The only reliable way to know if pregnancy has started is to take a pregnancy test. It will just work
This is because pregnancy tests detect human chorionic gonadotropin (HCG), an important pregnancy hormone. The body begins to produce it in larger quantities after implantation. Steady increases in HCG are a sign of early pregnancy.
Pregnancy loss
Although many pregnancies continue to full term, not all do. Around
Learn more about miscarriage here.
Fertilization is only possible when sperm has access to an egg. Anything that interferes with this can prevent conception. This may include:
- a low sperm count, which means there is a low volume of sperm in a man’s ejaculation
- sperm that are not motile, meaning they do not move or swim efficiently
- anovulation, which is when someone does not ovulate
- infrequent or irregular ovulation, which can make conception more difficult
- inflammation or damage to the ovaries or uterus
- blockages in the fallopian tubes
In IVF, conception can be prevented if fertilization does not occur successfully or if the embryos stop growing before a doctor implants them. Embryo quality can also be low, meaning there is a low chance of an embryo implanting in the uterine lining.
People can intentionally prevent conception through contraceptives, which are a group of devices and medications. They include:
- condoms
- diaphragms
- intrauterine devices (IUDs)
- hormone pills, patches, injections or implants
Learn more about the different types of contraceptives here.
People often use the term conception to refer to fertilization, when sperm fertilizes an egg. It can also refer to the overall process of becoming pregnant, which includes fertilization and implantation. A person is not pregnant until a fertilized egg, or zygote, implants in the uterine wall.
Conception can occur in several ways, both with or without the help of fertility treatments and reproductive technology.
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