While Terry Caldow adores her five-month-old daughter Ruby, she was not told her weight would render the emergency contraceptive pill useless when she went to get it.

Clinics and pharmacists are prescribing the morning-after pill to women, too embarrassed to warn them it is unlikely to work for any woman of above-average weight.

In May last year, Terrie Caldow, 33, had no idea her weight would mean the emergency contraceptive pill (ECP) would not prevent an unwanted pregnancy when she went to a sexual health clinic in Tauranga.

Weighing more than 70kg at the time, Caldow says she was not told her weight was a risk factor. The pill didn't work – she now has a five-month-old daughter.

DANIEL TOBIN/FAIRFAX NZ The emergency contraceptive pill is increasingly ineffective in women weighing more than 70kg, so why don't women know this?

Despite a warning issued by Medsafe in 2014, pharmacies are failing to warn women their weight could render the ECP ineffective.

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Pharmacies visited by women journalists, asking for the ECP, failed to follow the dispensing guidelines, which instruct them to refer women of above-average body-mass index to a doctor. And that experience was echoed by other women.

123RF Pharmacy Council best practice guidelines highlight a threefold increased risk of pregnancy for women who take the ECP with a BMI of 30 or higher.

The Medsafe warning was issued after research revealed the most popular type of morning after pill made from Levonorgestrel was ineffective in preventing pregnancies in women weighing more than 80 kilograms, and became increasingly ineffective in women over 70kg.

The Pharmacy Council of New Zealand then issued its own guidelines showing the risk of pregnancy was three times higher for women with a body mass index (BMI) of 30 or more, than those who were smaller.

The average New Zealand female over the age of 15 weighs 72.6kg, statistics from a 2011 University of Otago and Ministry of Health survey show.

Despite national best practice guidelines stating the ECP would be of "no advantage" to women with a BMI of more than 30, pharmacists still aren't warning women of the risks, and there is no legal obligation for them to do so.

One 25-year-old woman said she took the ECP six months ago.

A pharmacist took her into a meeting room to discuss whether she understood how the ECP works: explaining what it does and what side effects she might experience.

SUPPLIED Of three pharmacies visited by Stuff, none advised of the possible risks in heavier women until they were asked outright.

But there was no mention of weight, which in hindsight "was insane," she said.

Another woman, 23, has taken the ECP twice, most recently a year ago when she was "definitely over" 70kgs. She wasn't warned about the possible risk due to her weight either time. "The first time I took it my doctor gave me a prescription, and told me some of the issues, but didn't mention weight."

A 36-year-old woman said she weighed around 94kg when she went to a chemist for the ECP last year. "I was already taking the ECP later than I should have so the effectiveness was already low," she said.

MY DOCTOR ONLINE The copper IUD is a "far better option" for heavier women in need of emergency contraception, Family Planning's Christine Roke said.

The pharmacist did tell her of the increased risk from the delay in taking the pill, but again, weight didn't come into it.

She wouldn't have been offended if a pharmacist had asked about her weight: "It's more awkward telling a stranger that you've had sex and need the ECP than asking me what my weight is."

Journalists weighing more than 70kg, identifying themselves as women requiring the morning-after pill, visited three pharmacies this week to see if pharmacists were giving women all the information they need. None fully informed the women of the risks weight could play in the effectiveness of the ECP.

The Pharmacy Council's best practice guidelines say pharmacists "must ensure that all necessary advice and information is provided in an appropriate manner to enhance the woman's understanding, to enable her to make an informed choice".

They also suggest a pharmacist should refer a woman to a doctor or family planning clinic if there are any concerns about the efficacy of the ECP.

Medsafe general manager Chris James said: "Medsafe and the Medicines Adverse Reactions Committee reviewed the issue and considered that while there was a lack of conclusive evidence, women should be informed that Levonogestrel may not be effective for women with increased body weight."

Asking a woman about her weight is a "delicate" subject to approach, said Bob Buckham, chief pharmacist advisor for the Pharmaceutical Society.

While pharmacists are obliged to ensure women are fully informed of all risks associated with the ECP, there is no legal obligation to ask their weight, or even advise them, he added.

Instead, some pharmacists may size women up, he said, making a visual assessment, as opposed to using the scales.

"For some women it's already a very delicate, sensitive issue anyway.

"Some pharmacists possibly make a judgment call about the women they might have to explain this to, and others make an assumption that they don't need to explain it depending on the woman's size."

The notion that doctors and pharmacists might not be advising patients in an attempt to be inoffensive, made no sense to Caldow.

She would still have taken ECP if she had known it was less effective, but might have asked for a double dose, she said.

"It's crazy to think that was the difference between a baby or no baby," she said. ​

"I love, and adore, and idolise my daughter, and in hindsight, I am so glad the pill did not work, but I took the ECP to prevent a pregnancy."

Pharmacists, doctors and clinicians are required to ask a set of standard questions during each ECP consultation. These include when the woman had unprotected sex; where they are in their menstrual cycle; whether they have any medical conditions; and what medications they're taking or are allergic to.

But Family Planning's national medical director Christine Roke said the checklist was put together before the issues with weight were known.

"To be honest, I'm not sure whether it has weight on it."

In 2016, the Faculty of Sexual and Reproductive Health in the UK found doubling the dose in heavier women could mimic the efficacy of the pill in smaller women.

Their recommendation is that all women over 70kgs or with a BMI of 26 or more are given two levonogestrel pills, something that Family Planning had already been doing "on supposition," Roke said.

"There's certainly no harm in it - it may well be more effective," she said.

WHAT YOU SHOULD KNOW ABOUT THE EMERGENCY CONTRACEPTIVE PILL

The emergency contraceptive pill (generic name Postinor/Postinor-1) can be used up to 72 hours after unprotected sexual intercourse.

Levonorgestrel, the hormone in Postinor, is similar to the progesterone hormone made in the body.

The pill works by delaying the release of an egg to prevent pregnancy. It will not work if a woman is already pregnant. It cannot terminate a pregnancy.

There is another form of emergency contraceptive pill, ulipristal acetate or EllaOne, which is not available in New Zealand. It is not known to be affected by weight.

Medsafe are currently considering the drug for the New Zealand market, the Pharmaceutical Society said.

Last year, there were more than 11,000 emergency contraception consultations through Family Planning. Pharmac statistics showed a further 14,000 scripts were made out for the ECP in 2016.