Reflux in pregnancy is close to universal, mechanically inevitable, and genuinely miserable at three in the morning. It is also the label most likely to be applied to a different kind of upper abdominal pain — one that matters a great deal.
The short answer: progesterone relaxes the valve at the top of the stomach and slows emptying; later the uterus adds pressure. Up to 8 in 10 pregnancies are affected, worst in the third trimester. Antacids and alginates are the usual treatment and are widely used in pregnancy. Burning behind the breastbone is reflux. Pain under the ribs on the right side — especially with headache, visual changes or sudden swelling — is not, and needs a same-day call.
Why it happens
The lower oesophageal sphincter is a ring of smooth muscle, and progesterone relaxes smooth muscle. That is the whole first half of the mechanism: the door that keeps acid in the stomach is being held less firmly than usual, from early in the pregnancy, before there is any bump to blame.
The second half is mechanical and arrives later. As the uterus grows it displaces the stomach upwards and raises the pressure inside the abdomen, so there is both more push and less resistance. That is why heartburn that was occasional in the second trimester becomes nightly in the third, and why it often resolves within days of the baby being born.
What is normal
| Reflux | Ring the same day | |
|---|---|---|
| Where | Central, behind the breastbone, rising towards the throat | Under the ribs on the right, or through to the back |
| Trigger | After meals, on lying down or bending | Unrelated to eating or position |
| Character | Burning, with an acid or bitter taste | Severe, constant, gripping, or radiating to the shoulder |
| Response | Eases with an antacid | Antacids make no difference at all |
| With it | Nothing | Headache, visual changes, sudden swelling, vomiting, fever |
Call the same day if pain sits under the ribs on the right, or if upper abdominal pain comes with a headache, blurred vision or flashing lights, sudden swelling of the face or hands, or vomiting — after 20 weeks that is assessed as pre-eclampsia. Also ring for: vomiting blood or material like coffee grounds, black tarry stools, difficulty swallowing, unintentional weight loss, or chest pain spreading to the arm or jaw with breathlessness or sweating.
What helps
- Smaller meals, more often, and stop before you are full.
- Do not lie down for two to three hours after eating — this is the single most effective change for night-time reflux.
- Raise the head of the bed by putting something under the legs. Stacking pillows bends you at the waist and increases abdominal pressure, which is why it often fails.
- Sleep on your left side. It also satisfies the side-sleeping advice from 28 weeks.
- Space antacids away from iron tablets, since they reduce iron absorption.
Heartburn in pregnancy — at a glance
Progesterone relaxes the lower oesophageal sphincter and slows gastric emptying from early in pregnancy, and the growing uterus later raises intra-abdominal pressure — more push, less resistance. Up to 8 in 10 pregnancies are affected and it is usually worst in the third trimester, often resolving within days of birth. Antacids and alginates are the usual first treatment and are widely used in pregnancy; acid-suppressing medicines including some proton pump inhibitors are used on advice; sodium bicarbonate preparations are avoided, and antacids should be spaced away from iron tablets. Smaller meals, not lying down for two to three hours after eating, raising the head of the bed rather than stacking pillows, and left-side sleeping do most of the non-drug work. The distinction that matters is anatomical: burning behind the breastbone is reflux, while pain under the ribs on the right — particularly with headache, visual changes, sudden swelling or vomiting after 20 weeks — is a pre-eclampsia presentation and needs a same-day call.
Inside Baby Novum: meals, symptoms and sleep are logged together, so the meal that costs you a night usually identifies itself within a week — and blood pressure readings sit in the same record, which is what makes the right-sided pain question answerable rather than theoretical. Encrypted on the device, no account, no server copy.
Frequently Asked Questions
Why is heartburn so common in pregnancy?
Progesterone relaxes the ring of muscle at the top of the stomach that normally keeps acid down, so stomach contents move back up more easily. It also slows gastric emptying, so there is more in there for longer. Later, the uterus pushes the stomach upward and increases the pressure on it. Estimates commonly put reflux at up to 8 in 10 pregnancies, and it is usually worst in the third trimester.
What can I take for heartburn in pregnancy?
Antacids and alginate preparations — the ones that form a raft on top of the stomach contents — are widely used in pregnancy and are the usual first step. If those are not enough, acid-suppressing medicines including some proton pump inhibitors are used in pregnancy on advice. Ask a pharmacist or midwife and say how many weeks you are. Antacids containing sodium bicarbonate are generally avoided, and antacids can interfere with iron absorption, so space them apart from an iron tablet.
When is upper abdominal pain not heartburn?
When it sits under the ribs on the right side rather than centrally behind the breastbone, and particularly when it comes with a headache, visual changes, sudden swelling or vomiting. That combination after 20 weeks is a pre-eclampsia presentation and needs a same-day call. It gets attributed to heartburn constantly, which is exactly why it is worth knowing the difference in location.
Does heartburn mean the baby has hair?
There is a small study often cited for this and it is not a basis for anything. Heartburn is explained fully by progesterone and mechanics; treat it as reflux, not as a prediction.
What helps heartburn without medication?
Smaller meals more often; not lying down for two to three hours after eating; raising the head of the bed rather than piling up pillows, which bends you at the waist and makes it worse; avoiding your own triggers, commonly fat, spice, citrus, tomato, chocolate, coffee and fizzy drinks; and sleeping on your left side, which happens to place the stomach below the junction with the oesophagus.