Twin births are more common than ever. The overall match rate has increased by a third globally over the past four decades, driven primarily by Europe and North America.
The growing popularity of assisted reproductive technology (MAR) has facilitated this upward trend in multiple births – procedures such as ovarian stimulation tend to produce more eggs, while in vitro fertilization (IVF) can sometimes involve the transfer of several embryos to increase the chances of success.
In the USA, it was estimated than 36% of twin births and 77% of higher order multiple births (three or more babies) are the result of fertility treatments.
This global upward trend is likely to continue as treatments like this become cheaper and more accessible in low- and middle-income countries, where multiple embryo transfer IVF procedures are still more common compared to wealthier countries, where the trend is towards more single embryo transfers.
This is because twins and higher order multiple births are considerably more likely than single people born prematurely and with low birth weight – two well-established risk factors for higher infant mortality.
In Australia, there are no national multidisciplinary guidelines for the care of multiple birth babies that encompass the prenatal and postnatal continuum, and very little government-mandated education is provided to maternal and child health nurses to help them support and adapt services for multiple birth families.
But multiple birth babies face unique risks, underscoring the need in our hospitals for specific guidelines for the care of multiple birth babies and increased specialist care.
For example, our new study of more than 28,000 pairs of male-female twins born in Brazil shows that male twins are 60% more likely to die in their first year of life than their co-twins.
This is even after accounting for differences in birth weight and birth order, since previous evidence shows that being born first can reduce the risk of dying during or shortly after birth.
The increased relative risk for males in male-female pairs is exacerbated in the early neonatal period, and particularly for longer pregnancies for which the overall mortality burden is lower.
In other words, if a male-female twin pregnancy continues near term or beyond, both twins are more likely to survive, but if one were to die, that twin is much more likely. to be a man.
Existing evidence also indicates that sharing the uterus with a female rather than a male co-twin may be linked to improved early life outcomes and results of placental pathology too differ by gender in twin pregnancies.
The study of opposite-sex, or male-female, twin pairs may offer us an informative window into the role of gender differences in twin pregnancies and childbirth outcomes.
The new proof
Our findings, combined with previous data on developmental disadvantage for opposite-sex versus same-sex twin pairs, could be used to establish new guidelines in Australia tailored to the care of newborn same-sex and opposite-sex twin pairs.
For example, specific guidelines for the care of opposite-sex twins that take into account the different risk profiles between male and female newborns could help address preventable mortality.
In addition, counseling on the health and care of twins and their families, before and after birth, is needed to reduce the early life inequities faced by these infants.
Specific guidelines are important for public health
Twin pregnancies, births and early care usually require special attention from doctors and additional resources from clinics and hospitals.
These resources may not be readily available, particularly in some low- and middle-income countries where progress in improving reproductive, maternal, newborn and child health standards was slow.
Questions for future researchers include understanding how we can reduce twin admissions and length of stay in neonatal care units – as well as assessing whether physicians with specialist training in multiple gestations could lead to better pregnancy and childbirth outcomes.
However, existing and widely adopted guidelines for reducing neonatal mortality World Health Organization (WHO) fail to adequately address the specific risks of twin pregnancies, hampering efforts to increase awareness and understanding of the issues facing twins and their parents.
This is, again, arguably even more relevant in low- and middle-income countries, where infant mortality rates are high and twins are almost eight times more likely die than single people.
Although guidelines on twin and multiple pregnancies exist in developed countries such as UKlow- and middle-income countries would greatly benefit from similar initiatives.
Additionally, guidelines that can be disseminated and adopted globally could be an important first step in improving care for twins and their families.
These guidelines should highlight the sex-specific risks described above, although further research will improve our understanding of the pathophysiological basis of this disparity and the strategies that could be used to ameliorate it.
Throughout pregnancy and after birth, parents of twins are also at higher risk of experiencing symptoms of stress, anxiety and depression than single parents.
Research on parenting during the COVID-19 pandemic has also revealed the additional challenges faced by parents of twins and other children of multiple births.
While ensuring access to mental health care is essential to prevent and treat mental health problems, new parents and expectant parents of multiple births can also turn to parent organizations and other groups community support. worldwide for additional support.
In Australia, parents-to-be and new parents can contact the Australian Multiple Birth Association (AMBA) for peer support and learn more about the specifics of twin pregnancies in the free resources provided by Twins Research Australia (TRA).
TRA is the largest volunteer twin registry in the world, and twins and their families can join the register participate in new studies aimed at generating scientific evidence, with the potential to improve our understanding of many health conditions across the lifespan.
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