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NaturalCycles users : “Twin pregnancies, can they be planned?”

Today I got a very interesting question from one of our NaturalCycles users.

Her grandfather was a fraternal twin, which means that hyperovulation might run in the family. She is wondering if one can tell if more than one egg is being released in a cycle and hence plan/avoid having twins. Also Raoul and I were wondering if we would find more than one person in there, when we went for the first ultrasound last week. Raoul thinks it would be more “efficient” to have twins. I, on the other hand, was pretty scared to find two heart-beats in there, as I’d like to continue working on NaturalCycles shortly after the birth, and I think twins are more than a full time job on its own.

Questions from NaturalCycles users

Let’s first back up a little and see what causes pregnancies with multiples. As you probably know there are identical twins and fraternal twins. Identical twins emerge from one egg, fertilized by one sperm, which splits and forms two embryos. Identical twins therefore share the exact same setup of DNA. Fraternal twins occur when the woman releases two eggs within the scope of 24h, which both get fertilized by a sperm from the father. Fraternal twins are thus no more related than other siblings.

While studies have shown that having identical twins does not run in the family, having fraternal twins certainly does. Only the family of the woman’s side matter, as the fraternal twin gene causes hyperovulation. Usually a woman carrying such a gene does not release two eggs every cycle and in addition, the probability of both eggs being fertilized is rather small. Therefore there is definitely no certainty of actually having twins even if you do carry the gene.

There are other factors affecting the probability of having fraternal twins. The older a woman is, the higher the probability – the twin rate doubles for women above 35 years old. Also being above the average height and weight makes it more likely to have twins. The twin rates are quite different in different locations around the world, probably not only due to the variations in the genome but also due to different diets. In the US, the twin rate increased by 52% between 1980 and 1997 and reached 3% of all live births in 2001. More and more women taking fertility drugs and going through IVF explain part of the increase, but it might also be due to other factors like the increase of growth hormones in food. In fact, vegan mothers are only one fifth as likely to have twins as other mothers, probably due to the exclusion of dairy in their diet. This is even more pronounced in areas where growth hormones are given to cattle. The rate of having identical twins, on the other hand, seems to remain stably around 0.3% throughout time and location.

So let’s come back to the question. Can hyperovulation be detected by studying the fertility signs, such as measuring the temperature, LH hormone or cervical mucus? Unfortunately, this does not seem to be the case, at least not with the current technology available at home. Since the time between the two eggs being released is maximally 24h, as the progesterone increase followed by ovulation inhibits a second ovulation, it is very difficult to find any differences in the standard fertility signs. One must probably use ultrasonography to be able to detect it and that might get expensive if performed every cycle.

What it comes down to is thus simply a probability, which always can go either way. While identical twins mainly occur randomly, one can maybe affect the probability of having fraternal twins by controlling the age of when the conception occurs as well as the intake of diary products.

Temperature chart for a cycle that includes conception

Looking promising so far! A temperature chart for a cycle that includes conception is usually triphasic.

Firstly, the temperature rises with ovulation, and then the second rise is due to the further increased progesterone levels caused by the very early stage of pregnancy.

I am now 9 days past ovulation and implantation of the fertilized egg in the uterus should occur about now. My period is expected on Sunday and usually my temperature starts decreasing a day or two in advance, which means tomorrow. It will therefore be very interesting to see if the temperature will rise further tomorrow or if it will go down, implying that the higher levels today and yesterday were simply fluctuations.

Temperature chart - NaturalCycles