How to have twins
What is the probability of having twins? What factors increase the risk of twin pregnancy? Are there “miracle recipes”? Professor Yves Ville and Pr Jean-Claude Pons, two gynecologists and obstetricians, specializing in a twin pregnancy, were briefed.
Twin Pregnancy: What is the probability of having twins?
On the Internet, there are no longer the number of forum pages and indefinite articles that give tips of grandmothers to have twins. However, are they based on scientific evidence? What are the factors that influence the risk (or chance according to the point of view) of having twins? The question was asked of two gynecologists specializing in a twin pregnancy, Prof. Yves Ville and Jean-Claude Pons, members of the scientific committee of the association Jumeaux et plus.
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Sweet potato to have twins: a simple correlation link
On some websites, drinking milk or enriching her dairy diet is cited as one of the ways to increase her chances of having twins. These foods would increase the level of FSH (stimulating follicle hormone, which comes into play in ovulation), which would promote multiple ovulations. In reality, there is no solid evidence to date to support such a claim. The only food factor accepted by gynecologists is the high consumption of sweet potato or yam. These two plants possess a molecule close to estrogen, which would affect the female menstrual cycle.
As a major consumer of yams, Nigeria records a huge number of twin pregnancies, almost four times higher than the rate observed in France. It is not obvious to say that it is indeed the high consumption of sweet potato and yam that causes these twin pregnancies. Other factors would also be involved, according to Professor Yves Ville, gynecologist-obstetrician and head of department at the Necker Hospital in Paris. If nothing prevents to put the sweet potato in its menus when one wishes to have twins, not sure that it suffices.
Brightness: A Statistical Finding
Another factor is favoring: the photoperiod. Behind this barbarous name is the relationship between the duration of the day and the night. According to specialists, the greater the length of the day, the greater the risk of twin pregnancy. Only statistically, this correlation explains why Scandinavian women have more twins conceived in summer (where the sun does not set completely) than in winter, where the duration of sunshine is only a few hours. However, again, this is merely a statement, which deserves to be explained and refined by further studies. Know in any case that this factor could account for why there are more conceptions of twins in summer than in winter in France, even if this difference is small.
Heredity, multiparity, ethnicity: other factors influential but difficult to quantify
The first thing we think about when we talk about the probability of having twins is, of course, heredity. In the ordinary imagination, having twins in one’s family is undeniably a factor that increases the chances of having oneself. However, the reality is more complicated. There seems to be a link between heredity and twinning in families where many dizygotic twins, the twin sibs, are observed. This could be explained by the presence of several genes playing on the ovulation of women and leading to more polyovulations. For monozygotic twins or real twins, heredity is not established. It is not yet clear whether genes are involved in the separation of an egg, once the egg-sperm encounter has occurred.
Other statistical studies have shown that the more a woman has children, the more her chances of having twins increase. However, again, this is only a statistical observation, which can be explained by the increased risk of polyovulation.
The ethnicity also plays a significant role. All the specialists make the same comment: black women are more at risk of twin pregnancy than white women, who are themselves at higher risk than Asian women . There is thus a maximum of 6 births of twins per thousand in Asia, compared with 17 per thousand in France and up to 45 births of twins per 1,000 in Nigeria. It should be noted that these data can also be attributed to other factors, such as the duration of daily sunshine or even feeding.
Age and LMA: Two major twin factors
If all of the following factors are to be taken with tweezers, there are two others that are no longer to be proven: age and medically assisted procreation ( PMA ) treatments. The older a woman is, the more likely she is to have a twin pregnancy. At issue is a greater risk of polyovulation, that is, multiple ovulations where several ova are expelled into the uterus, instead of just one per cycle. If they are each fertilized by spermatozoa, these ova will give two embryos and two false twins, or twins dizygotic.
From 8 per thousand to 20-24 years, the frequency of twin pregnancies increases gradually until reaching a peak of about 14 per thousand around 37 years. The rate of twin pregnancies then decreases, due to more miscarriages spent 37 years. It is still higher (around 13 per thousand pregnancies) at 40 years of age compared to the frequency observed in the 20s.
The use of medically assisted procreation (PMA) is also a major risk factor for a twin pregnancy. According to Prof. Yves Ville, the use of PMA increases the risk of having twins par 5, or even 6. In the PMA pathway, two methods explain this increased risk: ovarian stimulation and the transfer of several embryos. The first is to boost the ovaries to force them to ovulate, which often leads to multiple ovulations. The second consists of selecting at least two embryos designed in vitro from the couple’s gametes and inserting them into the uterus. This approach generates 20% risk of twin pregnancy since both embryos have a chance each to implant.It should be noted that it also happens that we implant only one embryo, but that it splits in spite of everything in two and leads to multiple pregnancies.
However, for a woman under 30 years of white ethnic type, without a family history, without recourse to PMA and gynecological disease favoring multiple ovulations, the percentage of chance of having twins is about 1%.
We recommend reading the article: How to conceive twins naturally