Table of Contents
- Key Points
- Why This Research Matters
- How the Study Was Conducted
- Who Were the Patients?
- How Was Cancer Diagnosed and Staged?
- How Was Cancer Treated During Pregnancy?
- Outcomes for Mothers
- Outcomes for Babies
- What Do These Results Mean?
- Study Limitations
- Recommendations and Next Steps
- Frequently Asked Questions
- Source Information
Key Points
- UK CARING study analyzed 119 cancer-in-pregnancy cases from 14 centres (2016–2020).
- Breast cancer was most common (25.2%); gastrointestinal cancers had the worst prognosis (45.5% mortality).
- No patient received chemotherapy in the first trimester; 26.1% received chemotherapy later in pregnancy.
- Live births occurred in 81.7%, but 42.5% of live births were preterm and 53.1% delivered by caesarean section.
Why This Research Matters
Being diagnosed with cancer during pregnancy is one of the most distressing situations a woman and her family can face. It forces difficult decisions about treatment, timing, and the safety of both mother and baby. The number of women facing this situation is rising, driven by a global trend toward delaying pregnancy to later ages and the fact that cancer risk increases with age.
Researchers estimate that cancer occurs in between 17 and 27 per 100,000 pregnancies, which works out to roughly two new cases per day in the UK. Yet despite these numbers, there has been surprisingly little UK-specific data about how these cases are investigated, treated, or what happens to mothers and their babies.
One reason for this gap is that health registries do not routinely combine cancer data with pregnancy and childbirth records. Additionally, not all pregnancies end in a live birth, making it harder to track cases. Another modern twist: the increased use of non-invasive prenatal testing (NIPT)—a blood test that screens for foetal chromosomal abnormalities—has led to some asymptomatic women being diagnosed with cancer during pregnancy through incidental findings.
Pregnancy complicates every aspect of cancer care. Treatment plans must be adapted by a multidisciplinary team that includes oncologists, obstetricians, and family doctors, while also respecting the woman's own views and preferences. The UK's Royal College of Obstetricians and Gynaecologists (RCOG) provides guidance, but until now, there was no routine clinical data collection for cancer-in-pregnancy cases in the UK.
How the Study Was Conducted
The CARING study was a retrospective (looking back in time) analysis covering a five-year period from 1st January 2016 to 31st December 2020. It included women aged 16 and older who were diagnosed with cancer during pregnancy. The research was carried out through the National Oncology Trainees Collaborative for Healthcare Research (NOTCH), a network of oncology doctors across the UK.
Data was collected from 14 cancer centres: 10 in England, 3 in Scotland, and 1 in Wales. Together, these centres serve an estimated population of 21 million people. Initially, data was submitted for 144 patients, but after review, 119 patients were confirmed as eligible for analysis. Sixteen were excluded because the diagnosis fell outside the study period, and 9 were excluded because the cancer diagnosis was not actually made during pregnancy.
Information collected included how the cancer was discovered, what staging tests were performed, what treatments were given, and what happened to both mother and baby in the immediate period after birth. The data fields were mapped to the European INCIP (International Network on Cancer Infertility and Pregnancy) database, allowing international comparisons. Patients were identified locally through clinician recall or electronic coding, and approval was obtained from each site's Caldicott Guardian (the person responsible for protecting patient data). Because this was a retrospective study, patient consent was not required.
All analyses were performed using RStudio version 4.3.2 by an independent analyst. To protect patient anonymity, rare tumour types with fewer than five patients were grouped together in a "Other" category.
Who Were the Patients?
The median age at cancer diagnosis was 33 years, with a range of 22 to 49 years. This is similar to ages reported in previous international studies.
The most common cancer types were:
- Breast cancer: 30 patients (25.2%)
- Skin cancer: 25 patients (20.0%)
- Haematological (blood) cancers: 18 patients (15.1%)
- Genitourinary cancers (ovarian, cervical, urological): 14 patients (11.8%)
- Gastrointestinal (GI) cancers: 11 patients (9.2%)
- Other types (including ear-nose-throat, lung, thyroid, neurological, unknown primary): 21 patients (17.7%)
The vast majority—109 patients (91.6%)—were new cancer diagnoses. However, 10 patients (8.4%) had a cancer recurrence, meaning they had a history of cancer before becoming pregnant. Of these 10 recurrences, 4 were from a breast primary, and 3 of those were oestrogen receptor positive (ER+), a type of breast cancer that is driven by hormones.
Most women were symptomatic when diagnosed (82.4%), meaning they noticed symptoms that led to the diagnosis. But there was one striking exception: more than half (57.1%) of women with genitourinary cancers were asymptomatic, likely discovered through routine maternal screening programmes.
About three-quarters (76.5%) of patients were of white ethnic background, and just under half (49.6%) had never smoked. The median body mass index (BMI) was 24.9 kg/m². On average, women had been pregnant twice before (median gravidity 2, range 0–8) and had one living child (median parity 1, range 0–4). Notably, 34.2% were having their first baby (nulliparous). Most pregnancies (83.2%) were achieved through natural conception.
Compared with the international INCIP registry, the UK cohort had fewer first-time mothers (34.2% versus 44–56%). This matters because previous research suggests that having other children can be an important factor in decisions about continuing a pregnancy and delaying treatment.
How Was Cancer Diagnosed and Staged?
Staging—determining how far the cancer has spread—is crucial for planning treatment. In this study, the majority of patients (56.7%) had more than one staging investigation during pregnancy. However, a quarter of patients (23.3%, or 28 women) had no cancer staging investigations recorded during their pregnancy. The vast majority of these were skin cancer patients (20 of 28, or 71.4%)—specifically 11 basal cell carcinomas and 9 malignant melanomas—where staging may be less critical.
The most commonly used staging methods were:
- MRI or diffusion-weighted MRI: 60 patients (50.4%)
- Ultrasound: 55 patients (46.2%)
- X-ray: 21 patients (17.7%)
- Mammography: 19 patients (16.0%)
- CT scan: 16 patients (13.5%)
- Bone scan: 11 patients (9.2%)
- Endoscopy: 8 patients (6.7%)
- PET CT scan: none (0%)
It is reassuring that the most common staging methods (ultrasound and MRI) do not use ionising radiation, which is generally preferred during pregnancy. However, CT scans and bone scans do involve radiation exposure, and these are not usually recommended in pregnancy unless the benefits clearly outweigh the risks. The researchers note that future research is needed to confirm that when these scans were used, they adhered to specific safety guidance.
At diagnosis, cancer stages were distributed as follows: Stage I: 34 patients (33.0%), Stage II: 18 (17.5%), Stage III: 9 (8.7%), Stage IV: 20 (19.4%), with 22 patients (21.4%) having no stage recorded. Most patients (80.7%) were diagnosed at a stage where cure (radical intent) was still the goal.
How Was Cancer Treated During Pregnancy?
Deciding whether and how to treat cancer during pregnancy requires careful balancing of benefits to the mother against risks to the unborn baby. In this study, 57.1% of patients (68 women) received some form of anti-cancer treatment during pregnancy.
Chemotherapy was given to 31 patients (26.1%). Importantly, no patients received chemotherapy during the first trimester. Of those who did receive it, two-thirds (68.0%) received it during the second trimester, and the remaining 32.0% during the third trimester. This aligns with UK guidance that chemotherapy should be avoided in the first trimester but is considered safer from the second trimester onwards. Chemotherapy types included alkylating agents (16.0%), taxanes (15.1%), anthracyclines (11.8%), antimetabolites (7.6%), platinum agents (6.7%), and others (5.9%).
Surgery was performed during pregnancy in 44 patients (37.0%). Of these, about half (47.7%, or 21 of 44) were abdominal or cervical surgeries. The timing of surgery was most commonly in the second trimester (46.0%) or third trimester (40.5%), with only 13.5% in the first trimester. This is consistent with guidance that surgery can usually be undertaken at any trimester, depending on the tumour location.
No patients received radiotherapy during pregnancy, consistent with the general recommendation that radiotherapy is usually contraindicated in pregnancy, though it may occasionally be used in specific circumstances with foetal shielding. Other therapies—including targeted therapy, immunotherapy, hormone therapy, and steroids—were used in 10 patients (8.4%), and these are generally avoided until after delivery.
Treatment intent was radical (curative) in 80.7% of patients and palliative (aimed at controlling symptoms and prolonging life) in 16.8%. However, gastrointestinal cancers stood out: 63.6% of these patients were treated with palliative intent, meaning their cancers were already advanced at diagnosis.
Nearly half of the patients (42.9%) received no cancer treatment during their pregnancy at all. This was strongly related to how far along the pregnancy was at diagnosis: 56.4% of women diagnosed in the third trimester had no active treatment, compared with 35.9% diagnosed in the second trimester and only 2.2% diagnosed in the first trimester.
Outcomes for Mothers
The study tracked maternal outcomes up to the point of data collection at each site. Of the 119 women, 24 (20.2%) had died due to disease progression. This is a stark reminder of the seriousness of cancer during pregnancy.
Of the 95 women still alive at the time of the study:
- 75 (78.9%) were in remission
- 12 (12.6%) were receiving ongoing treatment
- 8 (8.4%) were lost to follow-up
Mortality varied dramatically by cancer type. The highest death rate was seen in gastrointestinal cancers, where 45.5% of patients died—likely because these cancers are often diagnosed late, as their symptoms (fatigue, abdominal pain, acid reflux) can be mistakenly attributed to the pregnancy itself. This phenomenon is known as "diagnostic overshadowing." Mortality rates for other groups were: "Other" cancers 38.1%, breast cancer 20.0%, haematological cancers 11.1%, skin cancer 8.0%, and genitourinary cancers 7.1%.
The 20% mortality rate for breast cancer in this UK study compares unfavourably with the 14% mortality rate reported by the international INCIP study. Similarly, UK patients received chemotherapy less often (26.0% versus 37% in INCIP), which the researchers suggest "may suggest an underutilisation of chemotherapy in a UK context and warrants further investigation."
Outcomes for Babies
Of the 119 pregnancies, the outcomes were:
- Live births: 98 (81.7%)
- Termination of pregnancy: 10 (8.4%)
- Miscarriage: 7 (5.9%) (the study abstract reports 8, or 6.7%, reflecting a minor discrepancy between the abstract and the full data table)
- Other outcomes: 4 (3.4%)
Delivery mode was recorded for the live births. Just over half were born by caesarean section (52 of 98, or 53.1%), a rate that is higher than the general UK population. The caesarean rate was especially high for gastrointestinal cancers (75.0%) and genitourinary cancers (90.0%).
Prematurity was common: 42.5% (34 of 80 live births with known gestational age) were pre-term (before 37 weeks). Of these pre-term births, 79% (27 babies) were delivered by caesarean section. This is an important consideration, as early delivery may be planned to allow cancer treatment to proceed, but prematurity carries its own health risks for the baby.
What Do These Results Mean?
This is the first pan-tumour (covering all cancer types) report of cancer diagnosed during pregnancy in the UK. It provides proof of concept that collecting national data on these cases is not only feasible but also essential for improving care.
Several findings stand out. First, the high rate of palliative intent and death in gastrointestinal cancers highlights a need for greater awareness that symptoms like persistent fatigue, abdominal pain, or reflux during pregnancy should not be automatically dismissed as normal pregnancy complaints. Women who have these symptoms should be evaluated carefully, and clinicians should maintain a high index of suspicion.
Second, the UK appears to use chemotherapy during pregnancy less often than international counterparts (26.1% versus 37%). While some of this difference may reflect patient choice or cancer biology, the researchers believe it deserves further investigation to ensure UK patients are receiving optimal treatment.
Third, the study underscores the value of close surveillance during pregnancy for women with a previous cancer history, particularly those with oestrogen receptor positive breast cancer, since 8.4% of the cohort were cancer recurrences.
Fourth, the discrepancy in breast cancer mortality (20% in this UK study versus 14% in INCIP) is concerning and warrants urgent exploration, even acknowledging that direct comparisons between studies can be challenging.
Study Limitations
As with any study, there are important limitations to consider. The NOTCH network is primarily made up of oncologists who treat solid organ cancers, so the representation of haematological (blood) cancer patients may be lower than expected in the UK population. If blood cancers are under-represented, the overall outcomes may not fully reflect the national picture.
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Frequently Asked Questions
How common is cancer during pregnancy in the UK?
Researchers estimate that cancer occurs in between 17 and 27 per 100,000 pregnancies, which works out to roughly two new cases per day in the UK. The number is rising because women are delaying pregnancy to older ages, and cancer risk increases with age.
What is the outcome for babies born to mothers with cancer during pregnancy?
In the CARING study of 119 pregnancies, 81.7% ended in live birth. However, 42.5% of live births were preterm (before 37 weeks), and 53.1% were by caesarean section. Prematurity carries its own health risks for the baby, and early delivery may be planned to allow cancer treatment.
Why are gastrointestinal cancers during pregnancy especially dangerous?
In the CARING study, gastrointestinal cancers had the highest death rate at 45.5%. They were often diagnosed late because symptoms like fatigue, abdominal pain, and reflux are mistaken for normal pregnancy complaints—a phenomenon known as 'diagnostic overshadowing.' Also, 63.6% of these patients were treated with palliative intent.
Can a previous cancer come back during pregnancy?
Yes. In the CARING study, 8.4% of patients (10 of 119) had a cancer recurrence during pregnancy. Of these 10 recurrences, 4 were from a breast primary, and 3 of those were oestrogen receptor positive breast cancer. Close surveillance is important for women with a history of cancer, especially ER+ breast cancer.
What does 'diagnostic overshadowing' mean for pregnant women with cancer symptoms?
Diagnostic overshadowing means cancer symptoms like fatigue, abdominal pain, or acid reflux are mistakenly attributed to pregnancy itself, delaying diagnosis. In this UK study, this was particularly seen in gastrointestinal cancers. Clinicians should maintain a high index of suspicion when these symptoms persist or are severe.
I'm pregnant and just been diagnosed with cancer—will a second opinion change my treatment plan?
A second opinion can be valuable when cancer is diagnosed during pregnancy because treatment decisions are complex and involve balancing risks to mother and baby. A UK review found that chemotherapy was used less often in the UK than internationally, and death rates for breast cancer during pregnancy were higher. For gastrointestinal cancers, symptoms were often mistaken for pregnancy complaints, leading to late detection. An independent expert review of your pathology, imaging, and proposed plan can help confirm that all safe options, including surgery and chemotherapy after the first trimester, have been considered. Diagnostic Detectives Network provides independent expert second opinions.
