Every parent of twins faces the question "Are your twins identical or fraternal? Many think that being identical twins refers to how twins look and not how they form. Take a look at the biology that determines the sex combinations that are possible with identical and fraternal twins. The terms identical and fraternal don't describe what the twins look like, but actually how they form.
Fetal sex determination in twin pregnancies using non-invasive prenatal testing
Can Identical Twins Be Different Sexes?
Battles between the sexes have been waged endlessly, but a study gave a definite edge to females. Researchers at the Helen Schneider Hospital for Women and the Sackler School of Medicine at Tel Aviv University in Israel concluded that outcomes for twin pregnancy are enhanced when at least one of the twins is a girl. The study evaluated more than 2, twin pregnancies and contrasted the outcomes for girl-girl, boy-girl, and boy-boy twins. The researchers found that the incidences of preterm deliveries were higher in boy-boy twins, and the babies had lower average birth weights and lower growth rates when both twins were male.
One of the first decisions for many couples is whether to have Down syndrome screening in pregnancy. For those who choose to test, there are 2 main options — non-invasive prenatal testing NIPT and the nuchal translucency. Although people usually think the screening is just for Down syndrome, we also screen for some other common chromosomal problems.