The Itch of Late Pregnancy, and What It Means for a Baby's First Breaths

New research from 2025 and 2026 measures how a mother's bile acid level affects her newborn, and looks at the baby's lungs before birth for the first time

Intrahepatic cholestasis of pregnancy is a liver condition of late pregnancy that causes intense itching and, more importantly, raises the level of substances called bile acids in a mother's blood. Those bile acids reach the baby, and when the level is high the pregnancy carries a greater chance of early delivery and of breathing difficulty after birth. Four studies published between October 2025 and June 2026 have measured that risk more precisely than before, and have looked at the baby's lungs on ultrasound while the baby is still in the womb.

What this condition is, and why the itching is not the dangerous part

Bile acids are made by the liver and normally travel into the gut, where they help digest fat. In some pregnancies — usually in the last three months — the liver stops moving them along efficiently and they build up in the mother's bloodstream instead. The most noticeable result is itching, often of the palms and soles, often worse at night, usually with no rash to show for it. Doctors call this intrahepatic cholestasis of pregnancy, or ICP; it clears on its own within days of the baby being born [1].

Here is the part that surprises most families: the itching itself, miserable as it is, does not harm the baby. What matters is the level of bile acids, because they cross the placenta into the baby's circulation. A large 2019 analysis showed that stillbirth risk only becomes measurably higher when the mother's level reaches 100 micromoles per litre or above, while the chances of early labour and of meconium (the baby's first stool) entering the amniotic fluid begin to rise from about 40 [2]. That is why care today revolves around a blood test rather than around how badly someone is scratching.

How families used to face this, and what changed

For a long time, ICP was treated as uniformly dangerous, and the standard response was to deliver the baby at around 37 weeks no matter how mild or severe the blood results were. The reasoning was understandable: stillbirth in this condition tends to happen late and without warning, and there was no way to tell which pregnancies were at risk, so everyone was treated as if they were. The cost was paid by the babies, thousands of whom were born early, with all the feeding difficulty, temperature instability and breathing trouble that brings.

Meanwhile, a small group of doctors in Italy noticed something else. In 2006 they reported that babies born to mothers with ICP developed respiratory distress syndrome — a breathing problem usually associated with premature lungs — more often than other babies born at exactly the same number of weeks [3]. That was odd: same maturity should mean the same lung problems. Two years later the same group washed out fluid from the lungs of affected newborns and found bile acids in it [4]. The bile acids were not just circulating; they were reaching the air sacs themselves. The team suggested they might be interfering with surfactant — the soapy substance that keeps those tiny air sacs from collapsing — so that a baby had enough surfactant, but not surfactant that worked properly.

It was a compelling idea, and it was never properly tested. Guidelines, when they were written, focused on preventing stillbirth and said very little about the baby's lungs [5][6]. The main medicine used, ursodeoxycholic acid, was tested in a British trial across 33 maternity units and 605 women, and did not reduce the combined risk of death, early birth or newborn unit admission [7]; a later re-analysis suggested it might reduce spontaneous early labour but said nothing about breathing [8]. So the question sat unanswered for nearly two decades.

How much does the number actually matter?

The first of the new studies is the largest. Researchers at a hospital in Guangzhou, China, looked back at 53,517 births over ten years, found 957 pregnancies with raised bile acids, sorted them into four groups by how high the level went, and counted what happened [9].

The pattern is dramatic. Taking the mildest group as the comparison, the chance of being born early was about the same in the next group up, roughly four and a half times higher in the group above that, and almost twenty-three times higher in the group with levels of 100 or more. Babies in that highest group arrived about three weeks earlier and weighed about 625 grams — nearly a pound and a half — less. Three-quarters went to the newborn unit, against about one in four in the mildest group.

One detail deserves emphasis, because it is easy to misread those numbers as meaning the babies were sick. They were mostly born early because doctors chose to deliver them early: in the highest group, 72 out of every 100 were delivered early on purpose, while the rate of labour starting on its own barely changed across the four groups. This is medicine making a deliberate trade — accepting the smaller, more manageable problems of early birth to avoid a rare but devastating one.

The mothers who never itched at all

The Guangzhou hospital does something unusual — it checks bile acid levels in every pregnancy, not only in women who report itching. Because of that, the researchers saw something hospitals elsewhere cannot: of the 957 affected pregnancies, 777 — more than four out of five — involved women with no itching whatsoever.

At mild levels, these women's pregnancies went better than those of women who did itch. But once bile acids reached 100 or above, the difference disappeared entirely: women who felt perfectly well had the same rates of early birth, meconium and newborn unit admission as women who had been scratching for weeks. The researchers' conclusion is blunt and worth repeating — at high levels, feeling fine tells you nothing. They recommend that women with this condition in a previous pregnancy, women carrying twins, and women with known liver or gallbladder problems have their bile acids checked whether or not they itch.

Looking at the baby's lungs before birth

The other three studies took a different approach: instead of waiting to see what happened after birth, they pointed an ultrasound machine at the baby's lungs beforehand. Two teams — one in New Delhi, India, one in Türkiye — measured the pattern of blood flow through the baby's main lung artery, and both found a clear difference between exposed and unexposed babies. In the New Delhi study of 100 women, 40 out of every 100 exposed babies developed breathing difficulty after birth compared with 18 out of 100 in the comparison group [10]. The Turkish team, studying 128 women, found the same direction of change [11].

A third team in İzmir, Türkiye, used a newer technique that measures how stiff a tissue is — the ultrasound equivalent of pressing on something to feel whether it is soft or firm. At 36 weeks they found the placenta, the baby's lung and the baby's liver all measurably stiffer in the 60 affected pregnancies than in the 60 comparison pregnancies [12]. Lung stiffness tracked very closely with how high the mother's bile acids had been — one of the strongest relationships anyone has reported in this field.

Why the researchers disagree, and why that is normal

The three teams agree that something is different about these babies' lungs. They do not agree on what it means. The New Delhi group reads their finding as a sign that the lungs are less mature; the Turkish Doppler group reads the same measurement as a sign that the lung's blood vessels are more relaxed, which could mean the lungs are maturing faster, not slower. The İzmir group has shown the lung tissue is stiffer without being able to say whether that reflects swelling, inflammation or normal maturation.

This kind of disagreement is not a sign that the research is bad. It is what the early stage of an unsettled question looks like: everyone can see the signal, and nobody yet knows how to read it. The consequence for families is that none of these ultrasound measurements should be used right now to predict whether a baby will have trouble breathing, or to decide when a baby should be born. They are research tools, not yet clinical ones.

What this means for you and your baby

If you have been diagnosed with this condition, the most useful thing to know is that your care team is watching a number, not your symptoms. Ask what your bile acid level is and how it is trending; that number, more than anything else, shapes the conversation about when your baby is born.

If your baby is delivered a little early and then needs help with breathing, that is not unusual and not a sign that anything went wrong. There is reasonable evidence that cholestasis contributes to breathing difficulty beyond what prematurity alone explains — which is precisely why researchers are still studying it. One practical footnote: the routine newborn blood-spot screening test can look slightly unusual in exposed babies. A study of 299 such newborns found small, consistent differences in their blood chemistry, and none had an actual metabolic disease [13]. If your baby's screen comes back needing a repeat, mention the cholestasis to whoever explains it to you.

What researchers are working on next

A study called CHOLE-RESP, running in a specialist newborn unit in Bucharest, Romania, is the first designed specifically to answer the lung question [14]. It is enrolling babies born to mothers with cholestasis alongside carefully matched comparison babies and testing their blood at 24 hours, two to three days and one week of age for markers of lung injury, with recruitment running until the end of 2027.

On the treatment side, a trial called OHANA tested a new drug designed to lower bile acids by blocking their reabsorption from the gut. It ran at 25 sites across New Zealand, the United Kingdom and the United States but was stopped early because too few women joined; only four received the drug. All four saw their levels fall substantially and all four had healthy babies [15]. Far too small a number to prove anything — but a drug that reliably brings the level down is exactly what is needed to find out whether lowering it protects babies.

Current summaries of the field point the same way: better tools to watch the baby before birth, and studies built around the newborn's outcomes rather than the mother's [16]. For now the message is a steadying one. The blood test guiding care is reliable, and the open questions are about refinement rather than about whether the basic approach is right.

References

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