Pre-eclampsia risk factor checker

The list nobody reads out to you

Somewhere in the first appointment, a midwife runs through your history and either does or does not mention aspirin. If she does, you may be handed a prescription and very little explanation. If she does not, you may never learn that there was a list at all.

The list is short, it is public, and several of the things on it are not conditions. Being pregnant for the first time is on it. Being 40 is on it. Having a ten-year gap since your last baby is on it. A first-time mother of 41 has two of the six moderate factors and meets the threshold, and in a busy booking appointment nobody may ever say why.

How the counting works

NICE splits the factors into high and moderate. One high factor is enough on its own. Moderate factors need more than one — the precise wording matters, because two qualify and one does not.

The high-risk list is genuinely medical: high blood pressure or pre-eclampsia in a previous pregnancy, chronic kidney disease, an autoimmune condition such as lupus or antiphospholipid syndrome, type 1 or type 2 diabetes, or chronic high blood pressure. Any one of those, and aspirin is advised.

The moderate list is the one full of ordinary facts: a first pregnancy, being 40 or older, more than ten years since the last pregnancy, a BMI of 35 or more at the first visit, a mother or sister who had pre-eclampsia, and expecting twins or more. Two of those together, and aspirin is advised.

Why aspirin, of all things

Pre-eclampsia is a disorder of the placenta. Early in pregnancy the spiral arteries supplying the placenta are meant to be remodelled into wide, low-resistance vessels. When that remodelling is incomplete, the placenta is under-perfused and releases factors into the maternal circulation that damage blood vessel linings throughout the body. That is why a placental problem shows up as high blood pressure, protein in the urine, liver and kidney changes and headaches: the target is the endothelium everywhere.

Low-dose aspirin acts on platelets and on the balance of prostaglandins involved in that process. It has to start early — NICE says from 12 weeks — because the window it is acting on is placental development, not the symptoms that appear months later.

The dose range, and why your friend was given a different one

NICE gives a range: 75 mg to 150 mg daily. That is deliberately wide, and units differ within it. If you were prescribed 150 mg and someone else was given 75 mg, neither of you was given the wrong dose. What matters far more than the exact milligrams is starting at the right time and continuing until the birth.

Do not buy it off a shelf in England

This trips people up. NICE notes that aspirin does not hold a UK marketing authorisation for preventing pre-eclampsia, and that community pharmacies in England cannot legally sell it as a pharmacy medicine for that purpose. It has to be prescribed. If this checker says you meet the threshold, the next step is your midwife or GP, not a supermarket.

The longer list of things that do not work

This is the part of NG133 that deserves more attention than it gets, because almost everything on it is still being sold to pregnant women.

NICE says do not use nitric oxide donors, progesterone, diuretics or low molecular weight heparin to prevent hypertensive disorders in pregnancy. It says do not recommend magnesium, folic acid, antioxidants — vitamins C and E — fish oils or algal oils, or garlic. And it says do not recommend salt restriction during pregnancy solely to prevent gestational hypertension or pre-eclampsia.

Folic acid appears on that list only in this specific context. It remains essential for preventing neural tube defects; it simply does not prevent pre-eclampsia. Similarly, salt restriction may be advised for other reasons, just not this one.

Is it safe?

This is the question most people actually want answered, and the short version is that low-dose aspirin in pregnancy is not the same proposition as taking painkillers. The doses here are 75 to 150 milligrams, against 300 to 900 milligrams in a standard painkilling dose, and the evidence base for it in pregnancy is large. It is one of very few interventions NICE recommends actively rather than merely permits.

People worry particularly about bleeding at the birth. Ask your team when they want you to stop, because practice varies and NICE's own wording is to continue until the birth of the baby. Ask too if you have a specific reason to be cautious — a bleeding disorder, a history of stomach ulcers, asthma that has been made worse by aspirin or ibuprofen in the past. Those are conversations with a prescriber, and they are the reason it is prescribed rather than sold.

What aspirin is not

It is not a treatment. Once pre-eclampsia has developed, aspirin is not what manages it — monitoring, antihypertensive treatment and ultimately the birth are. Aspirin reduces the chance of developing it in the first place, particularly the preterm form, which is the version that does most harm.

It also does not remove the need for the rest of antenatal care. Blood pressure and urine are checked at every appointment whether or not you are taking it.

Symptoms that override everything on this page

NICE recommendation 1.1.1 says to see a healthcare professional immediately with any of: severe headache; problems with vision such as blurring or flashing before the eyes; severe pain just below the ribs; vomiting; or sudden swelling of the face, hands or feet. That advice does not depend on your risk score, on whether you are taking aspirin, or on how many weeks you are.

Pre-eclampsia can develop in a pregnancy with no risk factors at all. A clear result here is a reason not to take a daily tablet; it is not a reason to ignore a symptom.

This checker counts published risk factors and applies a published rule. It does not diagnose anything, it produces no probability, and it does not replace the risk assessment your midwife does at the booking appointment.