All reasons the morning after pill doesn't always work as woman has twins despite taking it

A woman who took the morning after pill was rather surprised to learn afterwards that she was pregnant with twins, with her deciding to keep the kids and become a mother.

29-year-old Holly Firth had a one-night stand with a fellow guest at a friend's wedding and took the morning after pill afterwards, then 'thought nothing more' of the moment until a few weeks later.

She started thinking that the air freshener at work was unpleasant, and this sent alarm bells ringing so she decided to take a pregnancy test.

When she attended a scan she was told she'd be having twins, who were born on 27 February with Holly thinking it was 'meant to be'.

She said the morning after pill had 'never failed' her before, but explained that it 'doesn't work if you've already ovulated', and since her period was due on the day of her friend's wedding she reckons that's the reason why it didn't work.

There are a number of other reasons why the morning after pill isn't always effective.

The pills are not infallible, and there's a number of things which would throw them off (Getty Stock Photo)

Timing

According to the Cleveland Clinic, the most common reason that the morning after pill fails is due to when it is taken.

The sooner the pill is taken the more effective it is expected to be, and the NHS says that you should take it within a time window of three to five days after having sex.

They say that there are two main types of pill on offer in the UK, pills with levonorgestrel which must be taken within three days and pills with ulipristal acetate which need to be taken within five days.

It's no time to be playing the waiting game, the sooner you take the pill the better according to the experts.

The Terrence Higgins Trust says that the effectiveness of the morning after pill can drop from around 95 percent if taken within 24 hours of unprotected sex to about 85 percent in 48 hours, and down to 58 percent within 72 hours.

Basically, when it comes to the task of taking the morning after pill one ought to get on it as though it were the proverbial car bonnet.

There are many factors which can have an impact, time being one of the most important (Getty Stock Photo)

Weight

The Cleveland Clinic says that the morning after pill may be less effective if you're overweight.

Apparently if the pill contains levonorgestrel then women with a higher Body Mass Index may not find it to be as effective, though it seems that pills containing ulipristal acetate may not lose their potency in this way.

If you throw up within a couple of hours of taking the pill, you may need to go to a pharmacy and get another one (Getty Stock Photo)

Vomiting

According to the experts, if you throw up within a couple of hours of taking the pill then it can mean it doesn't have time to do its thing.

One of the side effects of the pill is that it can make you feel nauseous, but if you end up throwing up then you may need to take another pill.

While the advice is to only take one morning after pill, the NHS says that if you're sick within two hours of taking the pill then you should go and talk to a pharmacist to see if you need another one as 'you may need to take another dose as soon as possible'.

"This is going to be an expensive change to my life" (Getty Stock Photo)

Other medication

If you're already taking other medication then it might impact the workings of the morning after pill.

Certain types of barbiturates, which are often used as sedatives, and those containing St John's Wort, which is a plant that forms part of medication used to treat depression, have been suggested to make the morning after pill 'less effective'.

One of the earliest signs that the morning after pill didn't work is missing the menstrual cycle, and if a period is more than seven days late then taking a pregnancy test is recommended.

Holly's early sign was a heightened sense of smell, which does occur for many women during pregnancy.