Which twin is conceived first

Because fraternal twins form from separate eggs and sperm, this can lead to some uncommon circumstances in which the twins have different gestational ages or even different fathers. Sometimes hyperovulation happens a few days apart. After one egg is fertilized and begins to travel to the uterus for implantation, another egg is fertilized by sperm from a later incident of sexual intercourse. The result is fraternal twins who are conceived a few days apart.

This is known as superfetation. There have even been instances of fraternal twins with different fathers.

This occurs when a woman releases multiple eggs and has sexual relations with more than one partner. If an egg is fertilized by sperm from one man, and then another egg is fertilized by sperm from another man, the result is fraternal twins with different fathers. This phenomenon is called superfecundation. During pregnancy, the placenta provides vital sustenance to the baby.

In a multiple pregnancy with fraternal twins, a placenta develops for each baby. Sometimes, however, the two placentas fuse together and appear to be one single placenta.

Because they have their own placentas, fraternal twins are not at risk for some of the conditions that affect monozygotic twins, such as twin-to-twin transfusion syndrome TTTS or monoamniotic twins.

Each person receives half of their DNA from their mother's egg and the other half from their father's sperm, and so any two offspring will have some overlapping qualities. Monozygotic twins share the same genetic makeup, or genotype although their DNA is not necessarily identical. This shared DNA is what makes them often have remarkably similar appearances and characteristics. Unlike monozygotic twins, fraternal twins may look nothing alike, including having different:. Or, they may indeed be so similar that they are assumed to be identical, just as some siblings would be remarkably indistinguishable if they were the same age.

Twins and multiples are also shaped by their environment after they are born. Some similarities are enhanced because they are raised in the same home, share the same experiences, and are educated in the same schools at the same time. Because fraternal twins originate from separate conceptions, they can both be boys, both girls, or one of each just like a singleton baby.

Chromosomes from the father's sperm determine gender: XX for a girl and XY for a boy. As a result, the chances of fraternal twins resulting in boys, girls, or a combination are the same as for any other pair of siblings. Monozygotic twins, on the other hand, are always the same gender, either two girls or two boys. Twins are affected by your health and habits during pregnancy.

Fraternal twins share increased or decreased health risks due to sharing the pregnancy environment. While it's not possible to completely eliminate the risks that come with having fraternal twins, you can take some healthy steps to reduce those risks, including:. Your fraternal twins will share many things throughout their lives after starting out in the womb together. Enjoy their similarities and differences as they grow.

With these facts, you'll be able to tell them how they truly are unique. Get diet and wellness tips to help your kids stay healthy and happy. Columbia University Department of Obstetrics and Gynecology. Dichorionic twins. Flais SV. The difference between identical and fraternal twins. American Academy of Pediatrics. Updated November 7, Dizygotic twinning. Hum Reprod Update.

Body composition, smoking, and spontaneous dizygotic twinning. Fertil Steril. Adashi EY, Gutman R. Everyone has the same chance of having identical twins: about 1 in Identical twins do not run in families. But there are some factors that make having non-identical twins more likely:. IVF can increase the chance of twins, as more than 1 embryo may be transferred.

The most accurate way to tell if twins are identical is through a DNA test. This can only be done after your babies are born. The placenta could also provide clues. If your first ultrasound scan is done before 14 weeks, it should be possible to tell accurately what kind of placenta your twins have.

For more information on this and birth options, read about giving birth to twins. Read more about the different types of twins on the Twins Trust website. More detailed information on DNA testing and how to find out whether twins or triplets are identical is available on the Multiple Births Foundation website. This is because, if there are problems, it's easier and quicker to assist the delivery when the mother already has good pain relief.

If the first twin is in a head down position cephalic , it's usual to consider having a vaginal birth. However, there may be other medical reasons why this would not be possible.

If you have had a previous caesarean section, it's usually not recommended you have a vaginal birth with twins. If you have a vaginal birth, you may need an assisted birth , which is when a suction cup ventouse or forceps are used to help deliver the babies. Once the first baby is born, the midwife or doctor will check the position of the second baby by feeling your abdomen and doing a vaginal examination.

If the second baby is in a good position, the waters will be broken and this baby should be born soon after the first as the cervix is already fully dilated. If contractions stop after the first birth, hormones will be added to the drip to restart them.

You may choose to have an elective caesarean from the outset of your pregnancy, or your doctor may recommend a caesarean section later in the pregnancy as a result of potential complications. The babies' position may determine whether they need to be delivered by caesarean section or not.

If the presenting baby - the one that will be born first - is in a breech position feet, knees or buttocks first , or if one twin is lying in a transverse position with its body lying sideways , you will need to have a caesarean section. Some conditions also mean you will need a caesarean section; for example if you have placenta praevia a low-lying placenta or if your twins share a placenta.

If you have previously had a very difficult delivery with a single baby, you may be advised to have a caesarean section with twins. Even if you plan a vaginal birth, you may end up having an emergency caesarean section. In very rare cases, you may deliver one twin vaginally and then require a caesarean section to deliver the second twin if it becomes distressed. After the birth, your midwife will examine the placenta to determine what type of twins you have.

Twins can either be fraternal or identical. Depending on where you plan to give birth, you may need to go to another hospital with appropriate facilities if complications in your pregnancy indicate you're likely to have an early delivery. This may not be near to home, so make sure to check there are enough beds for both your babies in the neonatal unit.

Ask if your chosen hospital has a transitional care unit or a special care nursery. These are places that allow mothers to care for their babies if they need special care but not intensive care. These hospitals are more likely to be able to keep you and your babies in the same place. You might also want to ask if your hospital has cots that allow co-bedding where your babies sleep in a single cot , if this is appropriate and if you want your babies to sleep together.

If you have one baby in the hospital and one at home, you will need to think about splitting your time between the two.

When you visit your baby in hospital, ask if you can bring their twin and if co-bedding is allowed during visits. If you want to breastfeed and only one twin can feed effectively, you may need to express milk to feed the twin who is having trouble feeding. You may then need to put the twin who can feed on the breast to encourage milk production in order to get enough milk to feed both babies.

Check if your hospital offers support from a community neonatal nurse, which would allow for you and your babies to leave hospital earlier, for example if your baby is still tube-fed. When you go to clinics for follow-up appointments, it's a good idea to ask not to be booked into early morning appointments.