Why are There More Twins, Triplets and Multiples?

You may have noticed that there seem to be more families with twins, triplets or more babies popping up these days. It’s not just your imagination, there really have been more multiple births in the recent past than there were just 25 years ago.

Between the years 1974 and 1990, the incidence of twin births rose an average of 35% (per 100,000 successful pregnancies) throughout the developed world. In the same time period, the incidence of triplets and higher order births increased by a staggering 250%. In Canada alone, 126.67 sets of triplets were born in the year 1997. Compare this number to 1980 when there were only 49 sets born.

This incredible rise in multiple births is a cause for concern because the risk of certain complications increases for every extra baby in a pregnancy. Preterm labor is probably the most well known complication. Babies born before 37 weeks are premature, which puts them at risk of developing serious short and long-term health complications.

There isn’t just one reason for the multiple birth explosion, there are a number of contributing factors to this phenomenon.

Causes of Multiple Births
The natural rate of occurrence for twins is 1/89 singleton births. Triplets occur at a rate of 1/89 twin births, and so on. This is known as Hellin’s Law. Generally, family and personal history are the best indicators of fraternal twin births. Obese women are also more likely to give birth to fraternal twins.

As women age, their fertility begins to decrease. Once a woman passes thirty, her fertility begins to decline more quickly and her chances of having a multiple pregnancy increases. As it is becoming more common for women to wait until they have established a career before having a baby, the number of multiple births has naturally risen. Approximately one in three multiple gestations are attributed to the fact that the mother was over the age of 30 at the time of conception.

The remainder of this increase in multiple gestations is due to the prevalence of fertility enhancing drugs and invitro fertilization treatments (IVF). In the United States, approximately 56 per cent of births that result from infertility treatments are multiples.

Due to this staggering number of multiple births due to infertility treatment, doctors are realizing that there is a need to monitor and control the use of fertility drugs. This is being achieved through the use of ultrasounds to monitor egg production in patients using fertility drugs. If there is a possibility that several eggs are about to be released, the treatments are stopped.

Stricter guidelines and regulations for IVF are also being implemented. There is now a limit placed on how many embryos can safely be implanted during a round of invitro treatment, and how many rounds of treatment a woman can under go.

Thanks to these kinds of measures, there has been a steady decline in the rate of high-order multiple births in the last three years.

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