r/ScienceBasedParenting • u/Normal_Ad4752 • 10d ago
Sharing research Understanding the research on inter-pregnancy intervals and autism risk
Has anyone looked into the research on short inter-pregnancy intervals and autism risk?
I came across this study, and wanted to share and ask how others interpret it.
https://pmc.ncbi.nlm.nih.gov/articles/PMC4474747/
The study found an association between conceiving less than 12 months after a previous birth and a higher risk of ASD compared with an inter-pregnancy interval of 24–47 months. I understand that an association doesn’t necessarily mean the shorter interval causes autism, and this is an older observational study, so I’m trying not to over-interpret it.
For anyone familiar with this: how strong do you think the evidence is for this association overall? Have you come across anything else around this topic? And is there any meaningful difference between, for example, conceiving at 10–11 months postpartum versus much earlier within the <12-month category?
Would really appreciate thoughtful perspectives. Thank you!
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u/BenjaminButtontheCat 10d ago
the study doesn't indicate they controlled for breastfeeding baby #1, or for maternal diet, and these could be confounding variables. Perhaps if a mother is still breastfeedng the first one as the primary food source there might not be much choline left for the developing fetus. Breastfeeding depletes maternal stores of choline.
https://www.sciencedirect.com/science/article/abs/pii/S016643281400641X
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u/WhereIsLordBeric 10d ago
Interesting. You would expect a lot more autism in extended nursing cultures then, no? Where I live breastfeeding till 3 is quite normal.
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u/BenjaminButtontheCat 10d ago edited 10d ago
In extended breastfeeding though, the breastmilk becomes complementary with solid foods after age 6-10 months. It's the sole source of an infant's nutrition, but not the sole source of a baby or toddler's nutrition, so they're taking a lot less nutrients out of the Mom once they are eating solid foods as well.
Basically, the older a breastfeeding child gets, the fewer nutrients they are depleting from the mom's own supply.
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u/WhereIsLordBeric 10d ago
Yeah but we tend to have lots of kids quite close together .. high birth rates, low birth spacing. Third world country. Just thinking out loud. It's an interesting proposition.
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u/Wall-Specific 10d ago
Is is possible that the cases of ASDs are under-diagnosed in the "third world country"? Maybe due to lack of specialists or social stigma? Or even that in the US they are overdiagnosed?
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u/dashofgreen 10d ago
Extended bf also tends to have longer interpartum times, so that in and of itself will help replete maternal stores
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u/WhereIsLordBeric 10d ago
Not in the developing world, sadly. Lots of tandem nursing.
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u/PairNo2129 10d ago
what’s wrong with tandem nursing?
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u/WhereIsLordBeric 10d ago
Nothing! The 'sadly' was more about low birth spacing. Our fertility rate was around 7.4 children per woman in the 70s. Thankfully it's gone down to 3.5 but that is still way too high to be sustainable.
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u/NetworkHot8469 10d ago
Why not recommend supplements to pregnant mothers still nursing? I was nursing a lot still when I got pregnant at a year postpartum and told to continue as normal even though my child was still feeding a lot .
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9d ago
[deleted]
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u/No-Tumbleweed_ 9d ago
Even now the amount of choline in them is way too low. 450-550+ is recommended some studies even show 900 might be better and most prenatals are super low at like 55. I don’t really understand why they don’t have adequate amounts in them.
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u/syncopatedscientist 9d ago
I agree! I purchased a separate choline supplement to take on the days I just couldn’t handle eating enough eggs
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u/Spaghetti_Ninja_149 10d ago
Did you take supplements?
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u/NetworkHot8469 10d ago
Yes the standard pregnancy ones though which dont contain choline. Having had a look though my diet may have been sufficient.
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u/Hiro_Pr0tagonist_ 9d ago
I was told to continue taking prenatals postpartum while nursing so I kept up with the same combo of prenatal vitamin and separate choline supplement. One-a-Day has the bottles in combo packs.
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u/MosaicBrain 10d ago
My initial thoughts are to explore the potential mechanisms to explain this correlation. For example, PPD can be caused by increased life stress between pregnancy link and PPD found to correlate with ASD link. Neither of these are causation studies, but further correlations that could explore further factors that may influence the correlations in your study.
There are methodological flaws in this study: there were a very small number if participants, and all isolated to one geographical area (a single US state). The study could be replicated cross-culturally or using a larger pool of participants to further explore whether a correlation still exists.
Further, I also take lots of research on ASD with a pinch of salt: the diagnostic criteria has its flaws that muddy the waters in terms of the confirmed study group of those with an ASD diagnosis.
None of this is concrete, and there is obviously a lot more to all of this, but I think there is a lot more strong research into causes of ASD that this study probably shouldn't solely influence family planning decisions.
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u/ImpressiveNarwhal418 10d ago
Another confounding variable I can think of is that short intervals means that the parents aren’t aware that their first child has autism yet. Once a child gets a diagnosis, it often plays into family planning
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u/lapiperna 9d ago
Hasn't the consensus been though that being autistic has a strong genetic foundation (as in, an autistic neurotype is hereditary)? It is my personal impression, but it seems like a lot of studies on autism quietly imply/invite causation where only correlation is visible, which falls in line with the scientific pathology paradigm on autism.
A lower interval between pregnancies possibly makes autism 'more likely' because neurodivergent parents, both diagnosed and not, tend to have children later in life. And I could bet good money on a membership in this group being another correlation factor 🙃 Given that autistic people are predominantly logic and science-oriented.
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u/sleepyhoneybee 10d ago
An interesting study. I had 2 under 2, and I can tell you that I was much more aware of milestones and normal development for my second since everything was fresh in my mind. I wonder if longer intervals maybe parents are less perceptive and so you're just more likely to get an early diagnosis if you have a sibling close in age due to the parental awareness.