A multiple pregnancy means being pregnant with more than one fetus. It could be two, three, four or even more babies. A multiple pregnancy can pose health risks to the mother as well as the unborn babies.
Natural Vs Assisted Reproduction
A multiple pregnancy that results from spontaneous conception without any intervention is not common; it has become more common due to an increasing number of couples opting for assisted reproduction. For women who become pregnant naturally, only one percent of them will have a multiple pregnancy. However, for women who become pregnant through assisted reproduction, the chance of a multiple pregnancy is 20-40%.
Assisted Reproduction and Multiple Pregnancy
During a normal menstrual cycle, only one egg is released during ovulation, which may be fertilized by a sperm and form an embryo, later growing into a foetus. Multiple pregnancy can occur if the fertilized egg then splits into two or more embryos that would be identical. This is thought to happen by chance.
If more than one egg are released, which are simultaneously fertilized by sperms, it results in a multiple pregnancy and these babies are called fraternal. Fraternal twins tend to run in families.
Ovarian stimulation, is an intervention in assisted reproduction. A drug is administered to the woman, which stimulates the ovary and facilitates maturation of follicles and ovulation. The woman releases more than one egg, which may get fertilized and results in a multiple pregnancy.
With in-vitro fertilization, the eggs are retrieved and the sperm and egg are fertilized in a laboratory. The embryo that results is then implanted in the uterus. The treating doctor may transfer more than one embryo to the uterus resulting in a multiple pregnancy.
Multiple Pregnancy- Risk to the mother and babies
The mother’s health is at greater risk when carrying more than one baby. These women experience severe morning sickness, fatigue, and other symptoms of pregnancy. Other risks are the development of gestational diabetes, high blood pressure, preeclampsia and ecclampsia, breathing problems, backache and the risk of a miscarriage. In addition, there is the risk of needing a caesarean section for the delivery. After the delivery, the woman is at risk of bleeding from the greatly enlarged uterus that may fail to contract. While these are all risks, it’s important to remember that there are many women who have a multiple pregnancy that goes through without any of this or have this under control.
There are practical concerns as well, of having to breastfeed the babies and care for them through their infancy and childhood. A multiple pregnancy could also raise financial concerns. Parents may not be mentally prepared to take care of more than one baby, and may need support to provide for the babies and raise them.
A multiple pregnancy is associated with increased risk to the fetuses. The risk of preterm birth is high and the other risks include the risk of impaired growth and development, congenital abnormalities and the risk of still birth. Babies born before their expected date would be low birth weight and at risk of having developmental physical or cognitive disability if not cared for properly.
If you’re pregnant with more than one baby, you should see your doctor more often than you would if you were having just one baby. This is because you and your babies have a greater chance of developing serious health problems
Preventing Multiple Pregnancy
Preventing multiple fetuses in a natural pregnancy is not possible. However, it is possible to prevent it even with assisted reproduction. The ovarian follicles when over-stimulated may release multiple eggs, which mean there is a high chance of successful fertilization and a pregnancy thereafter. If the ovarian follicles are monitored properly, it is possible to have only one egg released during ovulation, resulting in single pregnancy.
With in-vitro fertilization, the fertilized eggs (embryos) continue to grow in the laboratory for up to six days before being transferred into the womb. The best one or two embryos will be chosen for transfer.
A Blastocyst is an embryo that has developed for five to seven days after fertilization and has 2 distinct cell types and a central cavity filled with fluid (blastocoel cavity). The further developed the embryos, the better the team is able to select the most viable embryos to transfer. This will reduce the need to transfer multiple embryos and run the risk of a multiple pregnancy.
The number of embryos to be transferred is decided by the couple after a discussion with their doctor regarding the embryo quality and how it would impact the risk of a multiple pregnancy. With advancing age of the woman beyond 32 years, implantation rate of the embryos tends to decline. While a singleton pregnancy is safest, it may be decided to transfer more embryos to avoid the risk of failure.
Assisted reproductive technologies are a boon for the couple with fertility issues, but it should be undertaken with complete information about what it involves.