Having a child puts a strain on relationships, but staying in an unhappy marriage is the best thing you can do for its long-term success, according to a study.Researchers found the majority of couples who are unhappy when their first child is born feel fulfilled a decade later. Seven in ten couples stay together following the birth of their first child despite being unhappy, according to the Marriage Foundation. What the heart wants…Credit:Alamy “Most marriages have their unhappy moments, but apart from the fortunately extremely rare cases where the relationship involves abuse, most couples can work through the difficulties to be happy later on.” Research commissioned by the organisation found that 68 per cent of these couples report being happy 10 years on. Moreover 27 per cent said they were “extremely happy”, giving their relationships a score of seven out of seven .At current levels, a child born today only has a 50 per cent chance of living with both parents by the time they reach 15, but the research suggests a “grin and bear it” approach may well prove fruitful in the long run.Harry Benson, from the Marriage Foundation, said: “Contrary to popular belief, staying in an unhappy marriage could be the best thing you ever do. Relationship experts confirm the findings of previous studies that suggested that couples who regularly had a night out with their partner were less likely to suffer from a relationship breakdown.Sir Paul Coleridge, a former High Court Judge and the founder of Marriage Foundation said: “With family breakdown – especially in the first ten years – at peak levels, this is really important, myth-busting research. “This study shows that because a couple is having a tough time adjusting to the demands of children, does not mean they will not come through it and end up with a really high-quality, high-satisfaction relationship in the long term.“The problem lies in the misconceptions around the nature of long-term relationships. They do not just happen. “Talk to anyone who has a satisfying relationship 20 years on and they will tell you that it has had to be forged by sensitive, hard work by both sides over time. “Keeping your relationship working and going forward is the far and away the best and most important ingredient in your child’s development.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings.