**4. In-vitro fertilisation**

In vitro fertilisation resulted in the first live birth in 1978. Since that time the use of IVF technology has changed dramatically and the increased success and its widespread use to treat all manner of subfertility issues has meant currently in Australia 1 in 25 children born are the result of an IVF cycle [25]. Like ovulation induction and super ovulation, IVF is associated with increased rates of unintended multiple pregnancy, in comparison to spontaneous conception, plus there is also a greater risk of an embryo splitting and resulting in monozygotic twinning.

their first few cycles and who have an expected high fecundity per follicle, but also patients for whom multiple pregnancy would be particularly dangerous. This includes women with an independent risk of pre-term birth and women with underlying medical conditions mak-

Super ovulation and IUI involves stimulating the ovary with ovulation induction agents with the aim to produce two follicles, then with ovulation trigger performing IUI to allow the sperm to bypass the cervical environment. It is usually performed in patients with unexplained subfertility or mild male factor subfertility. Consequently, the purpose of the treatment is to increase the chance of a successful pregnancy by increasing the number of oocytes

Given it is used in women that are already ovulating, prudent use of ovulation induction agents is imperative and careful monitoring of the cycle with ultrasound and oestrogen levels is important, as in ovulation induction, to prevent multiple pregnancy and higher order multiple pregnancy. Unlike ovulation induction, where the aim is to produce a single dominant follicle, super-ovulation is aimed at producing two follicles, with well controlled cycles accepting up to three follicles, but certainly no more. The reason is in this situation there is a potentially as yet unrecognised factor limiting conception, whereas in standard ovulation induction treatment for the anovulatory woman, it is only the absence of ovulation that is limiting conception, hence when that is overcome the woman should conceive. Once four follicles are present there is no increase in the live birth rate, but a significant increase in the

As the aim is to produce more than one follicle the risk of multiple pregnancy is high, higher than that is seen with IVF or ovulation induction. Overall rates of multiple pregnancy are around 14% in well controlled cycles, involving cancellation when more than three follicles are identified [24]. This is higher than is seen with IVF cycles, even in well controlled ovarian hyperstimulation protocols. Like ovulation induction the discussion regarding switching to an IVF treatment course, or cancellation of the cycle is required to be had with the patient prior to embarking on treatment. Often the decision around opting for IVF, to minimise the risk of a multiple pregnancy, or to adopt the cheaper treatment of super ovulation and IUI, but a greater risk of a multiple, revolve around the costs to the patient. This situation is unfortunate as the cost to the health care system and the family, ultimately, are greater when a multiple pregnancy results.

In vitro fertilisation resulted in the first live birth in 1978. Since that time the use of IVF technology has changed dramatically and the increased success and its widespread use to treat all manner of subfertility issues has meant currently in Australia 1 in 25 children born are the

ing them more susceptible to the pregnancy complications of multiple pregnancy.

**3. Super ovulation and intra-uterine insemination (IUI)**

multiple pregnancy and higher order multiple pregnancy rate [21].

ovulated and the availability of sperm.

52 Multiple Pregnancy - New Challenges

**4. In-vitro fertilisation**

While the key to reducing rates of multiple pregnancy with ovulation induction and superovulation and IUI lies with careful monitoring of the cycle and judicious cancellation of cycles when multiple follicles develop, the cornerstone to reducing multiple pregnancy rates in IVF treatment is to ensure single embryo transfer is the norm.

As IVF technology has developed and successful live birth rates have increased the need to transfer more than one embryo has rapidly declined. There is no significant difference in the live birth rate for women aged under 37 years undergoing a single embryo transfer (sET) compared with a double embryo transfer (dET), only an increase in the multiple pregnancy rate and subsequent increased pregnancy complication rate [26]. For women aged under 37 years the rate of multiple pregnancy with a double embryo transfer is as high as 25% [27], compared with less than 6% for women undergoing single embryo transfer [28].

Although implantation rate is not the gold standard by which to measure success of a fertility treatment, when compared with sET, dET has been reported to be associated with lower implantation rates suggesting a deleterious effect on the intrauterine environment when dET is employed [29]. This observation is further supported by the increased rates of poor pregnancy outcome when dET is performed but only one embryo implants. This scenario is associated with increased rates of growth restriction and preterm delivery compared with singleton pregnancies resulting from a single embryo transfer [30]. A review of the American Society for Assisted Reproductive Technology outcomes between 2004 and 2013, of over 180,000 IVF cycles concluded that although the live birth rate may increase with a dET, this is substantially out-weighed by the risk of multiple gestations [31]. They demonstrated that for patients with favourable prognostic factors; including younger maternal age, transfer of a blastocyst, and additional embryos cryopreserved, the gain in the live birth rate from sET to dET was approximately 10–15%, however, the multiple birth rate increased from approximately 2% to almost 50% for both fresh and frozen embryo transfer cycles.

Single embryo transfer is associated with not just a reduction in multiple pregnancy rates, but also a reduction in overall pregnancy complication rates with little effect on the live birth rate compared with double or higher number embryo transfer rates [32]. Double embryo transfer rates are occasionally recommended or supported when a patient has particular barriers to implantation success and thus have a perceived lower rate of risk to multiple pregnancy with dET. These may include advanced maternal age, poor embryo quality or multiple previous unsuccessful attempts at single embryo transfer.

The barrier to implementing universal single embryo transfer appears to lie in the cost of IVF treatment to the patient. In countries or regions where state funded or supported fertility treatment exists, the rates of single embryo transfer are far higher. The factor most influencing the likelihood a patient will undergo a single embryo transfer over a double or greater number embryo transfer is whether or not they have health insurance, a greater influencing factor than that of maternal age [33]. In Australia where fertility treatment is subsidised by the state and rates of health insurance are high, the rate of single embryo transfer is over 75% and reflected in the multiple pregnancy rate from IVF being below 6% [34]. In comparison, in the United States sET recorded in the same year was less than 25% [35]. This is also a reflection of the strict regulations that exist in Australia governing IVF treatment.

to the embryo splitting anywhere from Day 4 through to Day 8. Transfer in the middle of this time period involves subtle changes to the pH, temperature and nutrient environment that could explain the increased rate during blastocyst transfer. The actual mechanics of the transfer may also play a role in making the embryo more likely to split. Blastocyst transfer is associated with nearly a three times increased chance of embryo splitting and resultant monozygotic twinning compared with cleavage stage transfer [42]. This finding has not lead to a change in practice due to the significantly greater live birth rate seen overall with blastocyst transfer due to the ability to select an embryo that has survived until day 5 of development and also result in transfer at a similar time to when the blastocyst would be reaching the uterine cavity in a natural conception [43]. The increased rate of monozygotic twinning for blastocyst transfer is not replicated, or at least not as pronounced, when the transfer is a result of a frozen cycle, rather than a fresh transfer [41]. An explanation for this is the freezing/thawing cycle may harden the zona pellucida making the blastocyst more robust against the process of embryo transfer and reduce the chance of splitting. A regime of 'freeze all' may be worthwhile to further reduce rates of

Judicious Fertility Treatment to Minimise the Risk of Multiple Pregnancy

http://dx.doi.org/10.5772/intechopen.79288

55

Micro-manipulation techniques of the egg and embryo such as ICSI and pre-implantation genetic diagnosis have long been thought to play a role in increased rates of monozygotic twinning through weakening of the zona pellucida making it prone to splitting. Like blastocyst transfer, if this effect exists, it is likely associated with fresh transfers rather than frozen transfers. Because of this it is recommended that conventional IVF be used over ICSI unless

Embryo quality has an association with the chance of monozygotic twinning. Poorer embryo quality has been shown to increase the rate of monozygotic twinning [44]. An appreciation of this is important when considering double embryo transfer due to poorer embryo quality. An awareness that the resultant pregnancy may develop into a higher order pregnancy, such as a

Not all multiple pregnancies that develop after single embryo transfers are monozygotic. A review of twin pregnancies following single embryo transfer found 18% of twin pregnancies were dizygotic [45]. The explanation for this was likely concurrent spontaneous conception with a frozen transfer or ovulation of uncollected eggs and subsequent fertilisation with fresh transfers. This hypothesis is supported by the fact that unexplained subfertility, with an underlying chance of conception, and obesity, that increases chance of uncollected oocytes due to limitations of ultrasound, was the main risk factors for dizygotic twinning in this scenario. The importance of abstaining from unprotected sexual intercourse at time of transfer is imperative when counselling couples on how to reduce the risk of multiple pregnancy.

The rate of multiple pregnancy associated with ART has fallen steadily with the implementations of better practices. As pregnancy success rates have increased the belief that more follicles or more embryos equates to better outcomes has been disproven. Close monitoring of

multiple pregnancy from monozygotic twinning with blastocyst transfer.

significant male factor fertility issues exist.

**5. Conclusion**

dichorionic-triamniotic triplet pregnancy is crucial.

Regulations and policy governing single embryo transfer also exist in many Scandinavian and some European countries, such as Belgium, as well as Australia, with reflective low rates of multiple pregnancy and high rates of cycle success. The transfer of more than two embryos is banned in Australia and double embryo transfer only allowed in the setting of significant advanced maternal age or multiple failed attempts at single embryo transfer [36]. In comparison, other European countries like Greece, Montenegro and Lithuania have few regulations governing IVF protocols and treatment and overall data from Europe show rates of double embryo transfer well over 50% and rates of transfer of three or more embryos as high as 12.5% [37]. The multiple birth rate is reflected in this practice with the multiple birth rate following IVF being 18.7% in Europe compared with 5.6% in Australia and New Zealand [37]. The multiple birth rate following IVF is even higher in the United States at 26.6% [35]. This is despite slightly higher rates of double embryo transfer in Europe, however this is thought to reflect the high rate of fetal reductions that occur in Europe as a management strategy for multiple pregnancy.

Despite implementing a single embryo transfer an IVF cycle may still result in a multiple pregnancy due to monozygotic twinning. Monozygotic twins are at increased risk of significant complications including Twin-Twin Transfusion Syndrome (TTTS) and Twin Anaemia-Polycythaemia Sequence (TAPS), fetal anomalies and perinatal morbidity. The rate of monozygotic twinning is increased in IVF pregnancy by 6 times compared with spontaneously conceived pregnancies [38], occurring at a rate of around 2.5% [39]. The reason for this is likely multifactorial. Culture media, embryo quality, use of gonadotropins and manipulation of the zona pellucida are all thought to play a role in the increased rates of monozygotic twinning following IVF [40].

In natural conception the rate of monozygotic twinning increases with age, likely a reflection of egg quality, however the inverse has been seen in pregnancies conceived with IVF. Women under 35 are twice as likely to have a monochorionic twin pregnancy following IVF treatment compared with women aged over 35 [41]. The mechanism for this may include the zona pellucida experiencing increased thickening with advancing maternal age, resulting in the embryo of an older patient being more robust to the manipulation exerted on it during IVF or Intracytoplasmic Sperm Injection (ICSI), or during embryo biopsy. This is an important observation and further supports the argument for single embryo transfer for younger patients with a good chance of implantation per embryo transfer. If a patient is at increased risk of monozygotic twinning, and has a double embryo transfer the risk of a higher order multiple pregnancy, with the added complication of a monozygotic twin pair develops.

The stress that a developing blastocyst and embryo undergoes during an IVF cycle may rationalise the increased rates of monozygotic twinning. Monozygotic twin pregnancies are more likely in day 5 blastocyst transfer than day 2 or 3 cleavage stage transfer, perhaps reflective of the strain that may be put on the embryo the day of transfer. Monozygotic twinning occurs due to the embryo splitting anywhere from Day 4 through to Day 8. Transfer in the middle of this time period involves subtle changes to the pH, temperature and nutrient environment that could explain the increased rate during blastocyst transfer. The actual mechanics of the transfer may also play a role in making the embryo more likely to split. Blastocyst transfer is associated with nearly a three times increased chance of embryo splitting and resultant monozygotic twinning compared with cleavage stage transfer [42]. This finding has not lead to a change in practice due to the significantly greater live birth rate seen overall with blastocyst transfer due to the ability to select an embryo that has survived until day 5 of development and also result in transfer at a similar time to when the blastocyst would be reaching the uterine cavity in a natural conception [43].

The increased rate of monozygotic twinning for blastocyst transfer is not replicated, or at least not as pronounced, when the transfer is a result of a frozen cycle, rather than a fresh transfer [41]. An explanation for this is the freezing/thawing cycle may harden the zona pellucida making the blastocyst more robust against the process of embryo transfer and reduce the chance of splitting. A regime of 'freeze all' may be worthwhile to further reduce rates of multiple pregnancy from monozygotic twinning with blastocyst transfer.

Micro-manipulation techniques of the egg and embryo such as ICSI and pre-implantation genetic diagnosis have long been thought to play a role in increased rates of monozygotic twinning through weakening of the zona pellucida making it prone to splitting. Like blastocyst transfer, if this effect exists, it is likely associated with fresh transfers rather than frozen transfers. Because of this it is recommended that conventional IVF be used over ICSI unless significant male factor fertility issues exist.

Embryo quality has an association with the chance of monozygotic twinning. Poorer embryo quality has been shown to increase the rate of monozygotic twinning [44]. An appreciation of this is important when considering double embryo transfer due to poorer embryo quality. An awareness that the resultant pregnancy may develop into a higher order pregnancy, such as a dichorionic-triamniotic triplet pregnancy is crucial.

Not all multiple pregnancies that develop after single embryo transfers are monozygotic. A review of twin pregnancies following single embryo transfer found 18% of twin pregnancies were dizygotic [45]. The explanation for this was likely concurrent spontaneous conception with a frozen transfer or ovulation of uncollected eggs and subsequent fertilisation with fresh transfers. This hypothesis is supported by the fact that unexplained subfertility, with an underlying chance of conception, and obesity, that increases chance of uncollected oocytes due to limitations of ultrasound, was the main risk factors for dizygotic twinning in this scenario. The importance of abstaining from unprotected sexual intercourse at time of transfer is imperative when counselling couples on how to reduce the risk of multiple pregnancy.
