In the UK, parents of multiple babies receive no additional benefits
Families with multiple births face an extra burden of financial hardship and are more likely to have marital problems, a study suggests.
University of Birmingham research found parents who had twins, triplets or more babies at once were more likely to separate or divorce.
The Twin and Multiple Birth Association said it was more expensive and mothers found it harder return to work.
Researchers analysed the the annual Family Resources Survey for 2004-2007.
This data, which is a government source of statistics on poverty and low income, was analysed alongside the Millennium Cohort Study.
It found that 62% of multiple-birth families said they were financially worse off after their babies were born, compared with 40% of other parents.
And families who had experienced a multiple birth were nearly twice as likely to say they were finding the financial pressures "quite difficult" - 13% were in this category, compared with 7% of families whose children had been born singly.
Between 2004 and 2007, the poorest quarter of all families were living on £192 per week or less. However, the poorest quarter of families with twins or triplets had to get by with £181 per week or less.
And nine months after giving birth, mothers who had had multiple births were nearly 20% less likely to have returned to work than other mothers.
Many mothers reported that the cost of childcare for twins or triplets meant that their families would lose even more money if they returned to work sooner.
And the report revealed that parents of a multiple birth are more likely to separate or divorce.
Some 28% of multiple birth families who had been married had subsequently divorced or separated, compared with 24% for other families with children.
It emerged that financial distress tends to be among the most commonly cited reasons for family breakdown.
In the UK, parents of multiple babies receive no additional entitlement to benefits or parental leave.
By contrast, many countries take account of the different circumstances of those raising multiple birth children, both in terms on ongoing costs and one-off costs.
The Twin and Multiple Births Association (Tamba), which supported the research, wants government policies to change.
It has called for higher child benefit payments and extra grants for multiple births, as well as increased financial support for families who wished to use childcare and extended maternity and paternity leave for parents.
Keith Reed, chief executive of Tamba, said: "The main parties say they are committed to strong families, and helping mothers back to work, but many families with multiple births are in dire straits because successive governments have ignored their needs."
She said "urgent measures" were required to "ensure that the UK's twins, triplets and other multiple births no longer pay the price for a short-sighted one-size-fits-all approach".
"We call on the government to join other countries, like the Republic of Ireland, in supporting families of multiple births with common sense measures, including amendments to child benefit provisions and support for those who wish to use preschool or other childcare providers so that they can return to work," she added.
The Millennium Cohort Study, which was partly used by researchers for the study, is following a group of 18,500 children born in 2000/2001.
The annual Family Resources Survey, which was also used, covers more than 25,000 households with over 16,000 children, and is a source of statistics on poverty and low income.