Is twin A always born first?

No, Twin A is not always born first; while "Twin A" usually refers to the baby closest to the birth canal during pregnancy, their position can change, and they might be delivered second, especially in C-sections, though doctors often try to deliver "Twin A" first to keep the tracking consistent. It's a common convention for Twin A to be the firstborn in vaginal deliveries, but it's not a rule, and label-switching does happen, with rates up to 10% in some studies.

Which twin will be born first?

In prenatal ultrasounds, the baby positioned lowest in the uterus is given the designation of "Baby A." Under this convention, Baby A will likely be born first in a vaginal delivery.

Is the bigger twin always born first?

In addition, previous studies have shown that first-born twins are, on average, taller and heavier than second-born twins until adolescence (Silventoinen et al., 2007; Pietiläinen et al., 2002).

Does it matter which twin is born first?

Despite the clinical impression that firstborn twins do better than second-born twins, recent reports have shown no difference in perinatal mortality between them.

Is twin a always twin a?

Most often, fetuses known in utero as twin A are also first born and thus retain their label. However, this is not always the case, such that the twin A newborn was previously labeled twin B in utero and vice versa.

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Which twin is the eldest?

The twin born first is technically older by birth date, but medically they are considered the same age as they developed from the same pregnancy; however, cultural views vary, with some traditions (like some in China) considering the twin born last as older, as they were "deeper" in the womb. For most practical purposes and legal definitions, the one who emerges first is the elder, though many twins just consider themselves the same age. 

How to determine twin a and b?

Doctors determine Twin A and Twin B using prenatal ultrasounds, labeling the baby closest to the cervix (presenting twin) as Twin A, while the other is Twin B; this helps track them during pregnancy and birth, though their positions can sometimes swap, leading to potential confusion at delivery, especially with C-sections, as the first-born is officially Twin A post-birth, regardless of prenatal labels.
 

Can a baby have two fathers DNA?

Heteropaternal superfecundation is an extremely rare phenomenon that occurs when a second ova released during the same menstrual cycle is additionally fertilized by the sperm cells of a different man in separate sexual intercourse taking place within a short period of time from the first one 1-4.

Is one twin always more dominant?

“In most cases, one of the twins was almost always more dominant and more in control than the other. Also, one was usually more confident or willing to take charge in how they posed for their portrait.

Who carries the gene for twins?

The tendency for fraternal twins is genetic and carried by the mother, specifically a gene for hyperovulation (releasing multiple eggs) that she inherits from her mother or father, but it's the woman who ovulates multiple eggs who has twins, not the father. A father can pass the gene to his daughters, increasing their chances, but his own family history of fraternal twins doesn't directly affect his partner's odds, though factors like age, diet, and fertility treatments also play a role. Identical twins, however, are generally not genetic and occur randomly when one fertilized egg splits.
 

When do most twin moms go into labor?

You should be prepared for the possibility that your babies may come early and spend some time in neonatal care. Doctors consider 37 weeks to be full-term for most twin pregnancies. The average length of pregnancy for twins is 36.4 weeks.

Why do twins not go past 38 weeks?

Most patients with twins do not make it past 38 weeks due to labor, ruptured membranes, or some other compelling reason to deliver (hypertension or fetal growth restriction, for example).

Can two sperm fertilize one egg?

Yes, two sperm can fertilize one egg, a rare event called polyspermy, which usually leads to an unviable embryo with three sets of chromosomes, often causing early miscarriage. However, in extremely rare cases, it results in semi-identical twins (sesquizygotic twins), where a single egg is fertilized by two sperm, creating offspring sharing all maternal DNA but only some paternal DNA, a unique form of chimerism.
 

Which twin is the father?

A standard paternity test won't be able to tell which twin is the true father. Even a more sensitive ancestry-type test (like 23andMe) won't be able to answer this question. You'd need to look at each twin's complete set of DNA (all 6 billion letters!) and see if there are any random differences between them.

Do twin babies usually come early?

Yes, twins are very often born early, with over half arriving prematurely (before 37 weeks), usually around 36 weeks, much earlier than single babies (40 weeks). This increased risk of preterm birth is due to the greater demands on the mother's body and uterine environment, with the more babies carried, the higher the likelihood of an early delivery, sometimes requiring special care in a NICU, say experts at Brigham and Women's Hospital, KidsHealth, and Johns Hopkins Medicine.
 

Why can't you say siamese twins?

You can still say "Siamese twins," but it's outdated and often replaced by the more accurate and sensitive term, "conjoined twins," because the original term links to historical "freak shows," isn't geographically accurate for most cases (as it comes from Chang and Eng Bunker of Siam, now Thailand), and can feel dehumanizing, similar to outdated terms for other conditions. "Conjoined twins" is the preferred medical and respectful term for twins physically joined in utero. 

What gender of twins is most common?

The most common twin gender combination is boy-girl (mixed-gender) for fraternal twins, making up about half of those births, while overall, female twins are slightly more common than male twins due to higher male fetal loss in the womb; identical twins are always the same sex.
 

Can a woman have twins with two different guys?

It is possible for a woman to have twins, with each twin having a different father. This phenomenon is known as heteropaternal superfecundation. This can occur when a woman releases multiple eggs during her menstrual cycle and engages in sexual intercourse with different partners in close succession.

Can babies sense when their dad is gone?

Between 4–7 months of age, babies develop a sense of "object permanence." They're realizing that things and people exist even when they're out of sight. Babies learn that when they can't see their caregiver, that means they've gone away.

Can a baby have two biological moms?

Yes, two women can have a child with a biological connection to both partners through a process called Reciprocal IVF (or ROPA Method), where one woman donates an egg (genetic mother) which is fertilized with donor sperm and then implanted into her partner to carry the pregnancy (gestational mother), allowing both to be involved in conception. This shared IVF process creates a unique way for same-sex couples to experience both genetic and gestational motherhood within the partnership, though one partner provides the egg and the other carries the baby.
 

How much does a twin DNA test cost?

Only $119 with results in 3-5 business days

If you need to establish whether twins are monozygotic or dizygotic, we recommend Twin Zygosity DNA Testing. AffinityDNA offer a twin DNA test for just $119 with results emailed in 3-5 business days from receipt of samples.

What is the average length of a twin pregnancy?

The average gestation for twins is around 36 weeks, significantly shorter than the 40 weeks for a single baby, with most twin pregnancies ending between 35 and 37 weeks, making preterm birth very common (over half of twins arrive before 37 weeks). A full-term twin pregnancy is technically 39 weeks, but delivering around 37 weeks is considered successful and full-term for twins, with mature lungs and systems.
 

Do twins switch places in the womb?

Often, baby A (so named because she's closest to the cervix and therefore likely to be born first) will stay on one side while baby B stays on the other. The less room they have, the less likely they are to move around. But baby A may switch with B without your even realizing it (see, they're playing games already!).