Pregnancy headaches: why they happen and when they need assessment

Headache is one of the commonest physical complaints of early pregnancy, and for most people it is also one of the least worrying. The first weeks bring a steep change in hormone levels, a circulating blood volume that is already climbing, broken sleep, nausea that interrupts both eating and drinking, and very often an abrupt end to coffee. Every one of those is a recognised headache trigger on its own, and in early pregnancy they tend to arrive at the same time. The result is usually a dull, pressing, both sided headache that comes and goes across the day and responds to ordinary measures.

There is a second reason headache matters in pregnancy, and it has nothing to do with how common the ordinary kind is. In a small number of pregnancies a headache is the first thing a person notices when blood pressure is rising, and from around 20 weeks that possibility changes the urgency completely. This article keeps the two apart: what ordinarily causes a headache in pregnancy and what genuinely helps, and the particular pattern of symptoms that needs to be assessed the same day rather than slept on. The urgent list is placed near the start on purpose.

Why headaches are so common in early pregnancy

The headache of early pregnancy is rarely caused by one thing. It is usually the sum of several ordinary changes that happen to overlap in the first trimester, which is why it often improves when two or three of them are addressed together rather than when a single cause is found. Several ordinary changes contribute, and in any one person it is rarely clear which one dominates: the hormonal shift itself, disturbed sleep, reduced fluid and food intake because of nausea, the circulatory changes of early pregnancy, and the sudden withdrawal of caffeine in someone who has stopped coffee overnight.

Most of these headaches have the features of what doctors call a tension type headache. The pain is on both sides, described as pressure, tightness or a band around the head rather than as throbbing, and it builds across the day rather than striking suddenly. It does not usually come with vomiting, and bright light and noise are irritating rather than intolerable. Anyone who has had this kind of headache outside pregnancy will usually recognise it as the same thing, only more frequent.

Timing is reassuring in itself. Headaches that belong to the ordinary group tend to be worst in the first trimester and to ease as the second begins, because the hormonal curve flattens and nausea usually settles. A headache pattern that begins in the first weeks, fluctuates, and is gradually improving by the middle of pregnancy fits the common picture. A headache that is new in the second half of pregnancy, or that is getting steadily worse rather than better, does not, and belongs in the section that follows.

Headache in pregnancy that needs assessment the same day

Most of this article is reassuring. This part is not, and it sits here rather than at the end so that nobody reads past it. From around 20 weeks of pregnancy, and occasionally earlier, headache can be the presenting symptom of pre-eclampsia, a condition in which blood pressure rises after 20 weeks and one or more organ systems are affected with it. Most often that shows up as the kidneys leaking protein into the urine, but the liver, the blood, the nervous system or the placenta can be affected instead, so a clear urine test on its own does not settle the question. It can develop in someone who felt entirely well the week before. The first two steps in detecting it are measuring blood pressure and testing the urine for protein, which is exactly why those checks are repeated at every antenatal appointment.

• A headache that is severe, or that comes on suddenly and reaches full intensity within minutes
• A headache with visual disturbance: flashing lights, blurring, spots or sparks in the vision, or loss of part of the visual field
• Swelling of the face, around the eyes, or of the hands and fingers, particularly if it has appeared quickly
• Pain under the ribs or in the upper abdomen, often on the right side, with or without vomiting
• Heartburn that will not settle with the remedies that normally work for it, or vomiting that is new in the second half of pregnancy
• A sense of feeling generally very unwell that you cannot account for, alongside the headache
• A headache after 20 weeks that is not settling with rest, fluid and the ordinary measures described below
• A headache unlike any you have had before, one that wakes you from sleep, or one that is clearly worse on coughing, straining or lying flat
• Any headache with fever, a stiff neck, new confusion, weakness or numbness down one side, or difficulty speaking

If any of those applies, contact your maternity unit, your midwife, your obstetrician or your own doctor the same day, or go to the nearest maternity or emergency department if you cannot reach them and ask for your blood pressure and urine to be checked. That takes a few minutes and it settles the question. Do not wait for the next scheduled appointment, and do not decide to see how things look in the morning. A sudden headache described as the worst you have ever had, a seizure, collapse, or new weakness or speech difficulty is an emergency: call your local emergency number or go straight to an emergency department rather than arranging a visit.

Two further points are easy to miss. Pre-eclampsia and its complications can also appear in the days and first weeks after birth, so the same list applies postnatally, including to anyone whose pregnancy and delivery were straightforward. And the published wording genuinely differs here. The NICE guideline on hypertension in pregnancy, and the NHS patient pages, both ask people to seek advice immediately for a severe headache, the NHS adding one that does not go away with simple painkillers; the urgent maternal warning signs promoted by the CDC name a headache that will not go away or that is getting worse over time, without qualifying how severe it must be. Where thresholds differ, use the lower one: after 20 weeks, a headache that is not settling is a reason to have blood pressure and urine checked, whether or not you would call it severe.

Oestrogen, progesterone and the headache pattern

Oestrogen and progesterone both rise steeply from conception, and both act on structures involved in headache. Oestrogen influences the tone of blood vessels and modulates serotonin signalling in pathways that are central to migraine, which is why so many people can map their usual headaches onto their menstrual cycle. Progesterone relaxes smooth muscle throughout the body, including the walls of blood vessels. The nasal congestion and sinus fullness of pregnancy, which is often reported as facial or frontal headache rather than as a blocked nose, is thought to come from the effect of the pregnancy hormones on the lining of the nose together with the increased blood volume.

What seems to provoke headache is change rather than absolute level. A falling oestrogen level is the classic trigger of the headache many people get just before a period, and the rapid climb in early pregnancy can be disruptive in a similar way before the body adapts. That adaptation is the reason the pattern so often improves once the second trimester is established and hormone levels, although high, are relatively steady.

The other hormone of early pregnancy, hCG, is the one measured in blood tests and is covered separately in the article on hCG levels in early pregnancy. It is worth saying plainly that the intensity of a headache tells you nothing about how a pregnancy is progressing. People with severe first trimester headaches and people with none at all go on to have entirely ordinary pregnancies, and symptoms are not a measure of anything.

Blood volume, blood pressure and the circulation

Circulating blood volume begins to expand within weeks of conception and keeps rising into the third trimester, while the resistance in the blood vessels falls. The usual consequence in the first half of pregnancy is that blood pressure sits a little lower than a person's own baseline, sometimes noticeably so. That is a normal adaptation, but it is also why light headedness on standing up quickly, and a dull headache that eases on lying down, are both common complaints in the first and second trimesters.

This matters for interpretation. Blood pressure in the first half of pregnancy usually sits at or a little below a person's own baseline, which is why a first trimester headache is generally not a blood pressure problem, and why light headedness on standing is the more typical circulatory complaint at that stage. The picture reverses in the second half. Pre-eclampsia is defined in part by a new blood pressure reading after 20 weeks of 140 mmHg or higher on the upper number, or 90 mmHg or higher on the lower number, either one being enough on its own, taken properly and repeated, together with evidence of protein in the urine or of other organ involvement.

Neither of those numbers can be assessed from how a headache feels, which is the single most useful thing to understand about this symptom. A headache that would be entirely trivial in a person who is not pregnant can be the only outward sign of a blood pressure that has climbed, and a severe headache can accompany a perfectly normal reading. The measurement is the test, it is quick, it is part of routine antenatal care, and it is always reasonable to ask for it.

Caffeine withdrawal, the cause most often missed

This is the cause that is under recognised, and it is worth its own section because the fix is straightforward. Someone who has been drinking coffee or strong tea every morning for years has a nervous system accustomed to it. Stopping abruptly on the day a pregnancy test turns positive, which is a very common and well intentioned decision, commonly brings on a headache in a regular consumer, though not in everyone. It typically begins within a day of the last drink, peaks over the following day or two, is diffuse and pressing, and often comes with fatigue, poor concentration and low mood.

• The timing is the clue: the headache started within a day or two of cutting coffee, tea, cola or energy drinks
• It eases noticeably with a small amount of caffeine, which is informative but not a long term plan
• It is worst in the morning, when the interval since the last caffeine is longest
• Tapering over one to two weeks, by reducing the number of drinks or diluting them, avoids most of it
• Remember the hidden sources: strong tea, green tea, cola drinks, energy drinks, chocolate and some cold remedies

National guidance in pregnancy asks people to keep caffeine modest rather than to eliminate it: the NHS limit is no more than 200 mg of caffeine a day, roughly two mugs of instant coffee, which means a planned reduction is usually an option rather than a compromise. If the intention is to stop completely, do it over a week or two instead of overnight. Where a headache has already begun after abrupt cessation, it is self limiting and usually settles within two to nine days, and ordinary measures help in the meantime. If you take medicines that contain caffeine, or you are unsure how your own drinks add up, your midwife, doctor or pharmacist can work it through with you.

Dehydration, nausea and missed meals

Nausea in early pregnancy does more than make people feel unwell. It changes how much they drink, how often they eat and how evenly their blood sugar runs across the day, and all three of those are classical headache triggers. Someone who has been sick in the morning, has not managed breakfast, and has been sipping water reluctantly because fluid makes the nausea worse, has assembled most of the ingredients of a headache by midday without anything else going wrong.

The practical answer is smaller and more frequent rather than more. Fluid taken in small amounts through the day is usually tolerated better than a large glass at once, and food in the form of several small, bland, carbohydrate based snacks keeps blood sugar steadier than two or three main meals that are hard to face. Eating something before getting out of bed, which many people discover for themselves, works for the same reason. General guidance on eating patterns and hydration is set out in the article on nutrition and lifestyle.

There is a threshold at which this stops being a self care matter. Vomiting that prevents any fluid staying down, passing very little or very dark urine, weight loss, dizziness or feeling faint all point towards significant dehydration and need medical review rather than another attempt at dry toast. Persistent vomiting in pregnancy has recognised treatment, which is prescribed and supervised by a doctor, and asking for help early is sensible rather than excessive.

Sleep, posture and the muscles of the neck

Sleep in pregnancy is disrupted early and stays disrupted. Frequent waking to pass urine, nausea, vivid dreams, restless legs, heartburn and later on the simple mechanics of finding a comfortable position all fragment the night. Insufficient and broken sleep is one of the firmest triggers of tension type headache, and also one of the firmest triggers of migraine attacks in people who have them, so the same change helps both.

Posture contributes more than most people expect. As the uterus grows the centre of gravity moves forward, the lower back curve increases and the shoulders and neck compensate, which loads the muscles at the base of the skull that refer pain over the crown of the head and behind the eyes. Long hours at a screen, a phone held low and prolonged sitting all add to this. Breaking up sitting, raising a screen to eye level and gentle neck and shoulder movement several times a day often do more for this headache than anything else available.

Regular timing matters as much as total hours. Going to bed and getting up at roughly consistent times, keeping naps short and earlier in the day, and avoiding screens late are unglamorous measures with a real effect on headache frequency. None of this requires a product, and none of it needs to be done perfectly to be worth doing.

Migraine in pregnancy: the pattern can change in either direction

Migraine is a distinct condition rather than a severe headache. The pain is typically one sided and throbbing, it is made worse by movement, and it comes with nausea and a real intolerance of light and sound. Some people have an aura beforehand, most often visual: zigzag lines, a blind spot or shimmering that builds over several minutes and then fades, usually before the pain begins. Attacks last hours to days and leave a characteristic flat, washed out feeling afterwards.

In pregnancy the usual story is improvement. Many people with migraine without aura, particularly those whose attacks have tracked their menstrual cycle, find that attacks become less frequent or stop altogether from the end of the first trimester, which is consistent with the role of fluctuating oestrogen as a trigger. That is the pattern to expect, but it is not a rule. Migraine with aura behaves less predictably, attacks can continue unchanged, and some people have their first ever migraine during pregnancy.

Because the pattern can move in either direction, the useful thing is a record rather than an expectation. Note the date, the duration, whether there was aura, what preceded the attack and what helped, and bring that to appointments. It separates a migraine pattern that is simply continuing from a genuinely new headache, and it is the difference between a reassuring consultation and an uncertain one.

One point needs stating without hedging. A new aura, an aura that lasts longer than usual, an aura without headache in someone unused to that, or any neurological symptom that persists after the headache has gone, all need assessment rather than being attributed to migraine. The same applies to a first ever migraine like attack in the second half of pregnancy, because that is the window in which blood pressure needs excluding first. Tell a doctor, and let them decide what it is.

Telling the common patterns apart

The table below sets out how the usual patterns differ in practice. It is written to help you describe a headache accurately rather than to let you diagnose one, and the last column is the part that matters. No pattern in the table rules out a rise in blood pressure, which is established by measuring it and not by matching a description.

The row that catches people out is the last one. A headache caused by a rising blood pressure has no signature of its own, which is why the recommendation after 20 weeks is not to classify it at home. If a headache in the second half of pregnancy is persisting, escalating, or arriving with any of the features listed earlier, the next step is a measurement rather than another discussion about pain relief.

Measures without medication that genuinely help

Non drug measures are the sensible first step in pregnancy and they are not a token gesture. Many tension type headaches in the first trimester ease with them, and for people with migraine, keeping sleep, meals, fluid and caffeine steady is the part of management that is in your own hands, even though the evidence for it is weaker than the evidence behind prescribed treatment. They work most reliably when applied consistently and together rather than reached for once a headache has already taken hold, which is the main reason people conclude they do not work.

• Drink steadily through the day in small amounts rather than large volumes at once, and increase intake in hot weather or after vomiting
• Eat something every few hours, favouring bland carbohydrate when nausea is bad, and keep a snack by the bed for first thing
• Protect sleep: consistent times, a dark cool room, screens away before bed, and short naps earlier in the day if the night was broken
• Taper caffeine over one to two weeks rather than stopping on a single day, and account for tea, cola and energy drinks
• Move: a daily walk, breaking up long sitting, and gentle neck and shoulder stretches at a screen
• Use a cool cloth or a cold pack on the forehead, or warmth across the neck and shoulders, whichever suits you
• In an attack, a dark quiet room for an hour is a legitimate treatment and often shortens it

Two practical cautions. Avoid skipping meals in an attempt to control nausea, because that trades one symptom for another, and be wary of relying on painkillers regularly, since frequent use can itself maintain a daily headache in a cycle that is hard to break. It takes fewer days in the month to set that up with a triptan, an opioid or a combination painkiller than with a simple one, and either way it is regular use on most days, rather than occasional use, that does it. If headache has reached the point of regular medication, that is a conversation to have with your own doctor rather than a pattern to settle into.

It also helps to keep a simple log for two weeks: the days with headache, how long each lasted, what you had eaten and drunk, how you slept, and anything that preceded it. People are consistently surprised by what shows up. A trigger that is obvious in a written record is usually invisible in memory, and the log is the single most useful thing you can bring to an appointment.

Medication in pregnancy, and why this article recommends none

This article deliberately does not recommend a medicine, a dose or which products are considered acceptable in pregnancy, and that is not evasiveness. Choosing a medicine in pregnancy depends on the stage of pregnancy, on your other conditions and medicines, on whether you are breastfeeding, and on what the headache actually is. That is a prescribing decision, it belongs to the clinician who knows your history, and it cannot responsibly be made from a web page.

The practical rule is simple. Before taking anything at all for a headache in pregnancy, including something bought over the counter, something left in the cupboard from before pregnancy, a herbal preparation or a supplement, check it with your own doctor, your midwife or a pharmacist first. One caution is worth knowing before that conversation, because it is published public advice rather than a prescribing decision: painkillers containing codeine, and non-steroidal anti-inflammatory painkillers such as ibuprofen, are among those the NHS asks people to avoid in pregnancy unless a doctor has specifically prescribed them, so a packet left over in the cupboard is not a safe default. Which treatment is appropriate, and how much and for how long, remains a decision for the clinician or pharmacist who knows your history. Pharmacists are easy to reach and are a legitimate first stop for exactly this question. If you already take a regular migraine medicine, do not stop it or change it on your own: ask, because some medicines are reviewed or changed in pregnancy and others are continued, and the decision depends on which you are taking.

It is also worth knowing that preventive approaches exist for people whose migraine is frequent and disabling in pregnancy, and that they are assessed individually by a doctor, often with a neurologist involved alongside the maternity team. The relevant message is not that nothing can be done, but that what is done is chosen for the individual. Ask for a referral if headache is affecting your ability to work, sleep or function, because frequent migraine in pregnancy deserves a plan rather than endurance.

What your midwife or doctor will actually do

Knowing the shape of the assessment makes it easier to seek. Expect a short history first: when the headache started, where it is, what it feels like, how long episodes last, whether there is nausea, visual change or aura, what makes it better or worse, how you are sleeping and eating, and what caffeine and medicines you take. Then blood pressure, measured properly and usually repeated, and a urine sample dipped for protein. Those two measurements answer the question that matters most in the second half of pregnancy, and they take very little time.

Depending on the findings, blood tests may follow to check kidney and liver function and the platelet count, and an examination of the eyes, reflexes and limbs may be done if there is anything neurological to account for. Imaging is not routine for headache in pregnancy and is reserved for specific concerns, in which case the choice of scan is made with pregnancy in mind. If blood pressure is raised, the pathway shifts to monitoring and a management plan led by the maternity team, which may involve admission for observation.

Finally, a word about seeking help. People hesitate over a headache because it feels too minor to bother anyone with, particularly in a busy maternity service. That hesitation is the reason professional bodies have invested in campaigns naming headache among the warning signs worth raising. Nobody will think less of you for asking for a blood pressure check, the measurement takes minutes, and a reassuring result is a useful result. If something feels different from your own normal, say so plainly and ask to be seen.

Related Reading

• Earliest signs of pregnancy: what the hormone timeline actually allows
• Is diarrhoea a sign of pregnancy? What loose stools actually mean
• IVF Nutrition and Lifestyle: Before, During and After Transfer
• hCG Levels in Early Pregnancy and After IVF: What the Numbers Mean
• PMS vs pregnancy symptoms: how to tell them apart
• When does morning sickness start? The timeline in early pregnancy
• Cramps during pregnancy: what is ordinary, what is not, and when to ring

Sources and references

This article is supported by the following independent, authoritative sources:

• NHS: Headaches in pregnancy
• NHS: Pre-eclampsia
• RCOG: Pre-eclampsia patient information
• NICE NG133: Hypertension in pregnancy
• NICE CG150: Headaches in over 12s
• CDC: Urgent maternal warning signs