A question I am asked a lot. Here are several factors to influence whether or not twins run in families:
1) How many children you already have, i.e. after having two or three, Mom may have at least twins;
2) Age of Mom at conception, i.e. chances are higher of spontaneous conception (without fertility assistance) after the age of 30 and even higher after the age of 35 years. Having said that, I have worked with a 16-year old and an 18-year old, both of whom conceived twins spontaneously.
3) The closer they are to you in your Family Tree, the more likely it will be that you will conceive at least twins. So, if your grandmother or aunt had twins versus a second-cousin the chances of conceiving multiples would be higher.
4) MULTIPLES DO NOT SKIP A GENERATION. That is an Old Wives’ Tale. Important to be aware of.
5) Dizygotic (fraternal) twins occur because the Mother dropped at least two eggs in her fertility cycle and both were fertilized. There is always enough sperm available for fertilization, but there needs to be at least two eggs.
6) We do not know what happens to the fertilized egg to have Monogygotic (identical) multiples occur. It is rare, but not impossible, to have monozygotic triplets and quadruplets. The Dionne Quintuplets are the only recorded monozygotic quintuplets. I have a girlfriend who is a triplet and her brothers are monozygotic so what ever happened to their egg in the womb causing it to split, did not happen with hers. We do not always get to know everything. Also interesting with her birth is that they were their parents’ first children and they went on to have 7 more children, none of whom were multiples.
7) Multiples can have multiples. Happens more often than one would think.
8) If you have one set of multiples, there is a very good chance you will have another set in a subsequent pregnancy. We had one special Canadian family with 9 children, including 4 sets of twins!
9) Multiples begin at some point in families and start somewhere, so perhaps you are the lucky couple.
10) Just so you are aware, the gender of twins is generally broken down in thirds: 1/3 are boys, 1/3 are girls and 1/3 are boy/girl.
This amazing photo below shows how one family’s lineage worked out. It was shared by my friend Bonnie.
The lovely monozygotic young ladies in the back row are her daughters. Next to them stand their monozygotic twin cousins (sons of Bonnie’s youngest sister). In the front row are Bonnie’s husband’s nephew’s boy/girl twins. Next to them are dizygotic boys, belonging to Bonnie’s brother’s daughter. This family has two sets of monozygotic twins and two sets of dizyogtic twins…….so far!