Excess pregnancy weight gain tied to severe maternal complications: study
By Vikram JoshiLife Balance Correspondent, Peepals Shakti
Representative image: OsloMetX / Pixabay
A McMaster University study of over one million Ontario pregnancies, published on 22 October 2026, links gaining more weight than advised to severe maternal complications.
What Happened
Gaining more weight during pregnancy than guidelines recommend is linked to a higher risk of severe, sometimes life-threatening complications for the mother, whatever her weight before pregnancy, according to a study by researchers at McMaster University in Canada. The study, published in JAMA Network Open on 22 October 2026, used health records of more than one million pregnancies in Ontario between 2012 and 2022. The researchers said weight-gain guidelines, which were built mainly around babies' outcomes, should also be judged by what they mean for mothers.
Key Facts
- Published: 22 October 2026, JAMA Network Open, under the title "Weight Gain During Pregnancy and Severe Maternal Morbidity".
- Data: more than one million pregnancies recorded by the Better Outcomes Registry and Network (BORN) Ontario from 2012 to 2022.
- Weight gain: about 53% of pregnancies had weight gain above the recommended range and about 19% below it.
- Cases: the researchers identified more than 15,000 cases of severe maternal morbidity, meaning serious complications such as heavy bleeding, severe pre-eclampsia or admission to intensive care around childbirth.
- Finding: weight gain above the recommended range was linked to higher risk in every pre-pregnancy body mass index (BMI) group.
- Pre-existing conditions: women with conditions such as diabetes, asthma or high blood pressure had roughly double the risk of severe complications, and that risk rose further when weight gain fell outside the recommended range.
- Senior author: Laura Anderson of McMaster University.
Why It Matters
Severe maternal morbidity is the term doctors use for serious complications that threaten a mother's life or long-term health during pregnancy, birth or soon after. Such complications can affect a woman's health, work and family life well beyond the birth itself. Anything that helps identify women at higher risk early in pregnancy matters for health systems and for families.
Weight-gain advice in pregnancy is usually set according to a woman's body mass index (BMI) before pregnancy, a measure of weight relative to height. Most of the evidence behind those ranges came from studies of birth weight and babies' health. This study turns the lens to mothers. Its main message is that gaining more than the recommended amount carried higher risk across all BMI groups, so the concern is not limited to women who were overweight before pregnancy.
The study also points to how common the issue is: more than half of the pregnancies in the data had weight gain above the recommended range. The senior author argued that the answer cannot rest only on one-to-one advice at antenatal visits, and that wider, population-level strategies are needed beyond individual counselling.
The limits are important. This was an observational study: it shows a link between weight gain and complications, not proof that weight gain causes them, and other factors may play a part. The data come from Ontario, Canada, so the numbers may differ in India, where women's health and nutrition profiles are different. The study is not a guide for any individual. Every pregnancy is different, and the right weight gain for a woman should be decided with her doctor or midwife.
| Item | Finding |
|---|---|
| Pregnancies studied | More than one million, Ontario, 2012-2022 |
| Weight gain above guidelines | About 53% |
| Weight gain below guidelines | About 19% |
| Severe complication cases | More than 15,000 |
Impact
Short-term: The findings give doctors and expectant mothers another reason to track weight gain through pregnancy, alongside blood pressure and blood sugar, and to discuss it openly at check-ups.
Long-term: The researchers want weight-gain guidelines reviewed for mothers' health as well as babies', which could change advice and antenatal programmes if other studies confirm the link.
Who is affected: Pregnant women and those planning a pregnancy, especially women with diabetes, asthma or high blood pressure; obstetricians, midwives and health workers; and health planners who design antenatal care.
Key Takeaway
A study of more than one million pregnancies links gaining more weight than recommended to severe maternal complications at every starting weight, though it shows an association rather than proof of cause.
Questions and Answers
What did the McMaster study on pregnancy weight gain find?
Using records of more than one million Ontario pregnancies from 2012 to 2022, it found that gaining more weight than guidelines recommend was linked to a higher risk of severe complications for the mother, such as heavy bleeding, severe pre-eclampsia or intensive-care admission, in every pre-pregnancy BMI group.
How common was excess weight gain in the study?
About 53% of pregnancies had weight gain above the recommended range, and about 19% had gain below it.
Does this mean weight gain causes complications?
Not necessarily. It was an observational study, which shows a link but cannot prove cause, and its data come from Canada. It does not replace individual advice from a doctor or midwife.
Which women were at the highest risk?
Women with pre-existing conditions such as diabetes, asthma or high blood pressure had about double the risk of severe complications, and their risk rose further when weight gain fell outside the recommended range.
Disclaimer: Prepared by the Peepals newsroom from publicly available sources with AI assistance. Information is accurate to the best of our knowledge at the time of publication and may change. Images may be representative. Not professional advice. Report an error via our contact page.
By Vikram Joshi, Life Balance CorrespondentCovers Life Balance and more for Peepals Shakti. All stories by Vikram Joshi
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Vikram Joshi is a pen name of the Peepals Global Editorial Team, which researches, fact-checks and publishes every story. The portrait is an illustration.
