Dr. Aruna Ashok MBBS, MS OG, DNB OG
- Clinical Director
Aruna Ashok | 18 September 2025
A very few people understand the journey of an egg from ovulation to implantation. Its entire journey can be defined as miraculous; yet, it is also important to be aware of, especially for those trying to conceive.
When you visit the physician to seek their help to become pregnant, you might have heard them using the word “fertile window” more often. Well, this blog is for such people wondering what a fertile window is.
The fertile window is nothing but how long does the egg stay in the fallopian tube for potential fertilisation. Understanding how long it stays (viable for fertilisation) can be a game-changer in the process of conception.
We suggest that you continue reading to learn everything about egg lifespan.
Egg. A human reproductive cell typically starts its journey from the ovaries to the uterus. This journey usually happens for about 30 hours in the mid-cycle. The ruptured egg, on its way to the uterus, typically stays in the fallopian tubes for around 12 to 24 hours. It’s like halting for someone before reaching their destination.
For instance, if you have your period on the 1st of October, the egg may start its journey on the 15th of October.
Further, either fertilised or unfertilised, it continues its journey towards the uterus for implantation or dissolution.
Let’s learn the step-by-step journey of an egg in the female reproductive system.
Each month, your ovaries produce multiple follicles. These follicles would mostly be in the form of fluid-filled sacs. As days progress, usually in the middle of every menstrual cycle, they mature fully and rupture, releasing the egg. All fertility specialists call this occurrence an ovulation.
Even though multiple follicles grow and mature inside the ovaries, only one ultimately reaches the maturity size first and ruptures to release the egg. The mature follicle generally measures around 18 to 25 mm in diameter. As it reaches this dimension, it indicates that the follicles are mature enough for ovulation.
It is important to understand that each month, your ovaries alternate sides in producing follicles. For instance, if the right ovary produces follicles this month, it would be the left ovary’s turn to produce follicles in the next month. Even though the alteration is common, it isn’t always regular.
After the release, the egg enters the fallopian tubes, sweeping in by the fimbriae. Fimbriae are the finger-like structures of the fallopian tubes, which are visible at their very end.
Once swept in, the fallopian tubes drive the ruptured egg’s journey to reach the uterus through muscular contractions and cilia. The egg halts in the fallopian tubes for about 12 to 24 hours before reaching its destination (uterus).
Remember that the egg would be viable in the fallopian tubes for fertilisation only for 12 to 24 hours. If it fails to fertilise with the sperm in this short period (fertile window), it continues to move, but dissolves and is reabsorbed by the female body. Meaning, fertilisation does not happen in the uterus; rather, it happens only in the fallopian tubes.
Do you remember the moment when the egg was ruptured? Haven’t you wondered what would happen to the unruptured follicles?
Well, after ovulation, unruptured follicles would generally transform into a temporary endocrine structure, which is referred to as the corpus luteum. This structure stays in the ovaries and produces progesterone and estrogen hormones to thicken the uterine lining.
If fertilisation happens, the corpus luteum continues to produce higher levels of hormones and thickens the lining to develop the pregnancy. If fertilisation doesn’t take place, the corpus luteum degenerates by itself within 10 to 14 days. This reduces the progesterone and estrogen levels. As it reduces, it stimulates the discharge of the uterine lining, resulting in menstruation.
So, after ovulation, the destiny of your released egg is decided whether to develop into an embryo or degenerate as menstruation.
If the ruptured egg finds no sperm in the fallopian tubes during its waiting period, it starts to degenerate and be reabsorbed by the female body, typically within the fertile window. Upon failing to fertilise, the spiking levels of hormones return to normal levels. This triggers the shedding of thickened uterine lining by the corpus luteum, resulting in menstruation.
If the ruptured egg finds sperm in the fallopian tubes during its waiting period, it strives to let the healthy one inside it. The egg may transform its shape soon after the sperm penetrates its outer layer. This transformation helps prevent another sperm from entering its surface and causing polyspermy.
Polyspermy is the biological situation where more than one sperm enters the egg and makes it a non-viable embryo.
During fertilisation, the sperm’s chromosomes may potentially determine the embryo’s sex. If the sperm has an X chromosome, the embryo would be a girl. Conversely, if the sperm has a Y chromosome, the embryo would be a boy.
The fertilised egg (now an embryo) stays in the fallopian tubes for up to 3 to 4 days. Soon after fertilisation, it starts to change its shape by doing rapid cell division. It continues to divide further as it moves towards the uterus even after 4 days.
Once the embryo reaches the uterus, it strives to penetrate the thickened uterine lining developed by the corpus luteum. This occurrence is widely referred to as implantation. As it strives to penetrate, some women may notice light bleeding or spotting. This is named as implantation bleeding.
Soon after the successful implantation, the corpus luteum continues to produce higher levels of hormones. This further thickens the lining to develop the pregnancy.
As days progress, the outer cell of an embryo develops into the placenta, and the inner cells form into the embryo itself.
Following the implantation, your body starts to produce hCG (Human Chorionic Gonadotropin) hormone. This is otherwise known as a pregnancy hormone. The very same hormone is detected during the home pregnancy test. The negative result denotes the unsuccessful fertilisation and conception.
Couples who are trying to become pregnant should understand the journey of an egg from ovulation to implantation. Tracking how long the follicle stays in the fallopian tube can help you achieve your dream. Fallopian tubes play a significant role in the fertilisation process. Being informed of your reproductive functions can be a game-changer since it empowers you to know when to seek medical help.
1. What happens to the unfertilised egg after release?
If the egg is unfertilised, it starts to degenerate and be reabsorbed by the female body, typically within the fertile window (12 to 24 hours). It does not further try to reach the uterus. Rather, only a fertilised egg reaches the uterus.
2. Can the fertile window show any symptoms?
The answer to the question is yes. The fertility window does show the symptoms. However, not everybody experiences it. The symptoms may include clear and slippery cervical mucus, mild pelvic pain, slight increase in BBT (basal body temperature), breast tenderness, light bleeding, and heightened libido.
3. Which facility in Chennai has the best fertility specialists?
Several facilities in Chennai have the best fertility specialists. However, A4 Fertility Centre in particular has the finest specialists who have higher success rates and are skilled in handling advanced medical technologies.
4. What is the lifetime of a ruptured egg in the fallopian tube?
In the fallopian tube, the lifetime of the ruptured egg is typically around 12 to 24 hours. This is where the egg is more feasible for fertilisation.
5. What are the early signs of fertilisation?
The early signs of fertilisation may include mood swings, vaginal discharge, fatigue, nausea, breast tenderness, and cramping. However, these symptoms are not standard and may vary from woman to woman. Experiencing no symptoms can also sometimes be the early sign of fertilisation.
