Pregnancy is the most defining moment in a woman’s life. It is an exciting and challenging period for expectant mothers with many physical and hormonal changes happening in her body to support the development of the fetus and healthy pregnancy.
But what if something unusual happens? What if a woman becomes pregnant while she already is?
Sounds like a supernatural phenomenon. Right? But it can happen, and it does happen.
Believe it or not, though rare, there have been instances where some women have got pregnant, even while they were already pregnant.
Eager to know about this incredibly unusual phenomenon?
Let’s dive into the details.
Though most people are familiar with the basics of how a woman gets pregnant, here is a little guide for those who are not aware of the conception process.
How does pregnancy occur?
Ovulation, fertilization, and implantation are the three significant events for a successful pregnancy.
- During each menstrual cycle of a woman, one of the two ovaries releases an egg or ovum. This process is called ovulation.
- When a woman has unprotected sexual intercourse during the ovulation period, one of the sperm cells travels through the cervix and uterus into the fallopian tubes and fertilizes the egg. This process of penetrating and fertilizing the egg is called fertilization.
- The fertilized egg then travels down the fallopian tube into the uterus and attaches to the uterine wall. This process is called implantation.
Can a woman get pregnant again during pregnancy?
No. Except in rare cases, a woman cannot get pregnant during pregnancy.
Once a woman becomes pregnant, the hormonal and physical changes of pregnancy work together to prevent another conception.
Three distinct barriers prevent a woman from becoming pregnant again if she is already pregnant.
1. The ovulation cycle stops after pregnancy
The release of eggs ceases once a woman is pregnant. Once a fertilized egg successfully gets implanted into the lining of the uterus (endometrium), the hormonal changes alert the body to stop ovulation and the menstrual cycle.
2. Mucus plug inhibits sperm entry into the uterus
Typically, the cervix, located at the top of the vagina, acts as a gateway to the uterus. The cervix should be open enough for the sperm to travel into the uterus and fertilize the egg.
During early pregnancy, the cervical cells secrete a thick, jelly-like fluid called mucus which eventually accumulates and seals the cervical canal, creating a thick plug of mucus.
The mucus plug sits at the top of the vagina and acts as a barrier to stop any bacteria or other sperm from entering the uterus.
The sperm cells find it difficult to move past the mucus plug and reach the uterus after pregnancy.
3. The thick uterine lining prevents the implantation of the second egg
Usually, the fertilized egg must get implanted into the uterine wall for a successful pregnancy.
Once a fertilized egg gets implanted into the lining of the uterus (endometrium), it thickens considerably, making it more difficult for another fertilized egg to attach to the uterine wall.
Even if a woman has a double uterus, it will not increase the chances of superfetation. That is because high progesterone levels prevent the uterus lining from being receptive to another embryo.
If the ovulation continues after pregnancy, if the sperm manages to fertilize the egg and if an egg gets implanted into the uterine lining, it results in a strange phenomenon called superfetation.
What is Superfetation?
In simple terms, superfetation is when a woman conceives a second baby a few weeks after becoming pregnant with the first. A woman can get pregnant after two weeks of her first pregnancy.
With superfetation, a woman continues to ovulate even after pregnancy. Her ovaries release another egg that is fertilized and implanted, resulting in a second pregnancy.
Though superfetation is found to be common in some species of animals, it is extremely rare in humans.
Why is superfetation rare in humans?
Superfetation is a rare and unusual phenomenon in humans. For superfetation to happen, a series of uncommon events must occur.
1. The ovulation cycle continues after pregnancy
Ovulation is very uncommon during pregnancy because the hormones released during pregnancy result in the shutdown of a woman’s menstrual cycle, making it impossible for her to ovulate.
2. Sperm is present to fertilize an egg
Even if ovulation happens during pregnancy, the sperm must move past the mucus plug into the uterus to fertilize the egg, which is very unlikely.
3. The second fertilized egg gets implanted successfully on the uterine wall.
It is a rare situation where the second fertilized egg gets attached to the thick uterus lining resulting in the second pregnancy.
Only about ten cases of superfetation have been documented, in the medical literature to date. Of the few reported cases of superfetation, it is supposed to occur in women undergoing fertility treatments.
Is superfetation the same as carrying twins?
No. Superfetation is different from having twins.
Superfetation happens when two eggs belonging to different menstrual cycles are fertilized, at varying times. Having been conceived days or even weeks apart, the two babies differ in size and gestational age.
Twin pregnancy happens when two eggs are released and fertilized by two sperms in a single menstrual cycle. It can also occur when a single fertilized egg divides into two and develops into two fetuses.
As with twins, superfetation babies are born at the same time but depending on the length of time between the two conceptions, there is a higher risk of preterm birth for the younger ones. The older one will be much bigger than the younger one, as they had more time to grow.
Sometimes, superfetation may be mistaken for a twin pregnancy in an ultrasound, but it is not the same thing.
Superfetation Vs Superfecundation
Superfecundation is a phenomenon of twin pregnancy in which two or more eggs released during one menstrual cycle get fertilized by the sperms from separate acts of sexual intercourse, usually from two different fathers.
Superfecundation can happen when two separate eggs are released in the same ovulatory cycle and when a woman has sexual intercourse with two different men within the fertility window period. Since sperms can survive for a few days in the female reproductive tract, it is likely that the two eggs get fertilized and implanted in the same cycle. It results in twins with two different biological fathers.
Are there any risks of superfetation?
Superfetation carries similar risks as with any twin or triplet pregnancies. The main risk associated with superfetation is the preterm birth of the second baby due to the short gestation period in the mother’s womb.
As the delivery of the young baby occurs at the same time as the full-term baby, regardless of their gestational ages, this can result in problems like the low birth weight of the younger baby and other cognitive complications.
Superfetation, though rare, carries significant risks to the mothers as with twin pregnancies like high blood pressure and preeclampsia.
However, all cases of superfetation reported so far have been of twins that are 10 to three weeks apart, and the deliveries of both babies have been safe.
While many remarkable things happen inside a woman’s body while she is pregnant, superfetation is one of the rarest and the most surprising ones.
As the chances of superfetation are nearly impossible with one out of a few million pregnancies, there is no need to panic that it can happen to you.
If you think it happened to you, discuss it with your gynecologist to confirm the case. Advanced medical technology has made it possible to plan for both pregnancies to ensure the health of both babies, along with your health.
Featured image courtesy : https://www.invitra.com/en/superfetation/risks-of-superfetation/