28/06/2017 13:15 BST | Updated 28/06/2017 13:15 BST

Maternal PKU - Why I'm Having A Burrito Delivered To The Labour Ward

In my seventh month of pregnancy, like many mothers I'm looking forward to the moment when I can finally eat some of the foods I've missed.

I've not only had no sushi, no blue cheese, reduced caffeine and only occasional alcohol, I've also forsworn or seriously limited my intake of meat, fish, carbs including bread and pasta, cheese, beans, nuts, seeds, even soya-based meat replacements. I've carried scales with me to restaurants, sent dietary essays to friends who have hosted me, and done blood tests at home three days a week.

I'm not just a control freak; I have Phenylketonuria, or PKU, a genetic dietary disorder classed as a rare disease which affects approximately one in ten thousand people in the UK. I'm deficient in the enzyme that digests an amino acid called phenylalanine, common to high protein foods, so I restrict my intake of those foods and use supplements to get the nutrition I and now my growing baby need.

Every child born in this country is tested for PKU. Most people forget about it when it doesn't show up for their baby. The NSPKU describes the risks it carries as follows: "Sustained, high blood levels of phenylalanine can harm the brain and without early and effective treatment children with PKU can develop learning difficulties and developmental delay."

I was 'on diet' from birth to the age of 25 and thanks to the efforts of my parents this never felt like as great a hardship as it might have, but it was difficult for them and made me aware that I needed to be more independent about diet and food at an early age. The obscurity of the condition saw even family members try to persuade me that 'a wee piece of fish' would do no harm (it would); the supplements I took made a school friend sick when he insisted I let him try them, and as for turning down all of the food so carefully prepared by friends' mothers at children's birthday parties... My mum and I ran the gauntlet of seeming judgemental and difficult in an age when gluten intolerance and coconut milk belonged only in the health food stores so opposed in spirit to the bright pastel icing and Bananarama soundtrack of the eighties.

At 25 I went 'off diet' because my specialist permitted it. My form of PKU isn't the most severe (some people are allowed barely any natural protein; I can tolerate more) and he had to judge a whole range of nutritional factors, like the fact that I was managing my diet badly and risking other problems.

This was on the understanding that if I wanted children, I'd need to go back 'on diet' before conception, but I put that thought out of my mind because I had things to discover: my first steak, almost bloody I had it so rare; the sweet juiciness of prawns added to my usual vegetable curry recipes; the lazy joys of pizza and other fast foods I'd not been allowed as a teenager at sleepovers. After a few years of frenzied excitement eating everything I possibly could, sometimes in great quantities, I even enjoyed going on 'a diet' like other people would, obeying rules about food based not on protein content but calorie content.

Then the day came when my husband and I were ready to try for children. We went to the 'metabolic kitchen' and learned a strict version of the diet to avoid a frightening list of risks a PKU mother runs if a high concentration of phenylalanine crosses the placenta. This can interfere with the normal development of a baby and result in long-term or permanent damage. The main abnormalities associated with high blood phenylalanine in the mother are: congenital heart disease, damage to the brain, a small head, a low birth weight (under 2,500g), or even a non-viable pregnancy.

Fast forward a year and more and here I am, with a wish list as long as my arm of the foods I've gone without. My husband knows that upon successful delivery of our child I will expect an extra spicy chicken burrito, a Nando's delivery, some lobster linguine, a lasagne, and a three bean salad in vinaigrette. Maybe not all at once.

Once I've had my binge, I'm thinking of staying on diet, albeit not as strictly. I can't do myself as much damage as I would my child, but I've enjoyed some of the effects of managing my levels and I know that I'd be taking less long-term risk with my health, which will matter to my child too.

There's also the chance that my little girl might have PKU. If so, I hope she will have the same support from her family, friends and dedicated healthcare workers I have enjoyed. If you're pregnant and reading this, raise a chicken drumstick to all those who help me and others like me be healthy and have healthy children. It's a miracle of modern medicine and it's left me in awe, if a little bit jealous of what's on someone else's plate from time to time.

28th June is International PKU Day. Find out more at