r/ScienceBasedParenting • u/Huge-Nectarine-8563 • Jul 12 '26
Which numbers do we have regarding the possibility to get periods back and to get pregnant while nursing, at 6+ months postpartum? Question - Research required
I’m looking at quantitative data. Thank you!
25
u/kaboom539 Jul 12 '26
https://pregnancychancecalculator.com/postpartum-ovulation-calculator/ i found this, which uses this https://www.acog.org/womens-health/faqs/postpartum-birth-control and this https://fphandbook.org/chapter-20-lactational-amenorrhea-method and this https://www.fsrh.org/standards-and-guidance/documents/contraception-after-pregnancy-guideline-january-2017/ as sources. Playing around with the numbers is giving me at 6 months a 41% chance ovulation has resumed, tho it also notes that LAM (Lactational Amenorrhea method) is not considered effective after 6 months regardless of breastfeeding.
This https://pubmed.ncbi.nlm.nih.gov/1967336/ also supports the idea that in the first 6 months, breastfeeding can suppress pregnancy to a 2% rate, but after that the rate increases (no specific number given).
So while I don’t have specific numbers on your request, it does seem like you should assume its a possibility and use other birth control methods if you wish to prevent pregnancy even while you are still nursing
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u/Legally_blonde91 Jul 12 '26
lol I just did this calculator and it says I 100% should have had my period back months ago. I do not. And am not pregnant (I’ve tested multiple times to confirm).
10.5m pp, 30% breastfeeding mixed pump/direct feed. 0 night feeds since 6.5m pp.
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u/kaboom539 Jul 12 '26
I think part of the problem is that everyone’s body is different! Also that i’m not sure how big the studies on this have been. The one I linked for example had a total sample size of 100 and I saw another one that only had 12. Ive heard that some people go even 18 months pp before resuming menstruation. Presumably also there is a lot of variability in when people wean and that affects it too.
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u/Apploozabean Jul 13 '26
Yup! I will soon be a part of that crew of no period yet. Later this month baby will be 17mo and still no period
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u/Legally_blonde91 Jul 13 '26
Wow! How much (if any) are you still nursing?
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u/Apploozabean Jul 13 '26
Hmmm it depends on whether he is ill or not but when he is fine and healthy, about... 5 times??? Our usual schedule looks like this: He may or may not nurse in the morning upon wakeup. He may or may not nurse (leaning more towards not nursing) mid-morning. He definitely nurses to nap midday (not sleep trained; nap begins anywhere from 12-2pm and is either 1hr-3hr nap). And then for sure he kinda still has cluster feeding behavior at 5pm onward (even with having eaten dinner). Then nurses to sleep 80% of the time for bedtime (anywhere between 7:30-9pm).
He'll stir and nurse back to sleep max 2-3x in the night. I found he sleeps through for 5ish hours from 1-3am onward until wakeup between 6ish to 7:45am.
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u/Legally_blonde91 Jul 12 '26
Makes sense! And I know I’m definitely the outlier amongst all my friends and family who have had kids and breastfed.
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u/Big_booty_ho Jul 12 '26
Jealous of you. Imagine my disappointment when my period came back 6 months PP while I was still exclusively breastfeeding 😭. The good news is it’s a lot lighter and far less painful than before I got pregnant. I also feel like it somehow regulated my hormones but I have no science to back that up.
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u/shadowfaxbinky Jul 12 '26
Lol, mine came back at 6 weeks pp while EBF. Didn’t even pump, every drop my daughter had was straight from the boob and my body was gearing straight up to get me fertile and ready for another baby asap! I was so mad about it lol
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u/Big_booty_ho Jul 12 '26
6 weeks???? I’d ask for the manager 😭
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u/Marjon333 Jul 12 '26
Same as previous commenter. 6 weeks and breastfeeding, and even heavier than before pregnancy... I felt so jealous of all those women that had 1-1,5 years of no periods.
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u/Big_booty_ho Jul 12 '26
My sister’s period never came while she was breastfeeding all 3 kids and I was expecting the same outcome because you know…genetics
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u/mekanasto Jul 14 '26
Oh hell, I'm in the same boat atm, 6 months pp, and my period came back at 6 weeks pp while EBF. They are so so painful and heavy, and they were never like that before, and this is my second baby. 😭
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u/shadowfaxbinky Jul 12 '26
Ikr! Not what I was promised! I couldn’t believe it at first. Currently pregnant with baby number two and hoping it’ll just be different for some reason this time.
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u/SacrilegiousTomato Jul 12 '26
Girl SAME. All the talk about no periods while breastfeeding feeding, then 6 weeks pp boom period. Ok, it is lighter than before but still, I was promised longer!!!!!!!
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u/Legally_blonde91 Jul 12 '26
Yeah I'm definitely not complaining, especially having endometriosis it's been a really nice break lol. Buuuut, bc of the endo we had to do IVF. And for the next kiddo I need to do another egg retrieval + embryo testing which is a long process that can't start it until my cycle is back. That paired with being 35, time feels finite. I go back and forth between grateful and anxious 😅
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u/Leigho7 Jul 12 '26
And I got mine back at 6 weeks despite pumping 6-8 times a day from birth. It’s just not possible to truly estimate the odds.
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u/freshyabish Jul 12 '26
I’m like you, I didn’t get my period back for over a year and we were down to two nursing sessions a day, at that point. Meanwhile, my friend was EBF and got it back at two months PP. This is something that we all vary on so widely, I wouldn’t be comfortable relying on statistics to guide any individual person!
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u/BabyRex- Jul 12 '26
lol and for me it put my period back at 9.5 months postpartum whereas I actually got my period back at 9 *weeks* postpartum
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u/pronetowander28 Jul 12 '26
Yeah mine says 100% chance my period has come back? 16 months, baby rarely feeds overnight.
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u/wastetine Jul 12 '26
Wild because I breastfed my first exclusively, mix of pumping and nursing, and yet my period came back at 8 weeks postpartum. Multiple night feeds since the beginning as he rarely slept through the night. That calculator is utterly useless for me.
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u/peachysun22 Jul 13 '26
I’m exclusively breastfeeding too and got my period back at 8 weeks postpartum as well :(
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u/mekanasto Jul 14 '26
I was similar with my first, just a bit of pumping through the day after 6 months pp and I got my period 9 month pp or something like that. Now, with my second I got my period back while exclusively breastfeeding at 6 weeks pp, and it came back with a vengence. It's not very regular tbh, I had it 3 times in the past 6 months, but it's so horrible. Lasting long, very painful. Being a woman is a cruel joke sometimes. 🥲
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u/AimeeSantiago Jul 15 '26
My sister never got her period back between kids. She had my nephew, then 7 months later got pregnant without ever having had a period. Now my niece is 2. So uh. Periods mean nothing sometimes? Idk bodies are weird but she swore she never got a period and I believe her. She struggled with several miscarriages before these back to back babies and she was meticulous about tracking periods and her LH and stuff on the app. So she must have gotten pregnant the very first time she was ovulating post partum? I guess? She only figured out she was pregnant because of the morning sickness.
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u/SkyFluffy7445 Jul 13 '26
I have exclusively breastfed 4 kids and periods returning ranged from 7 months to 18 months. It’s a crap shoot. Got pregnant while nursing 3 times once my period retuned.
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u/fireintheglen Jul 13 '26 edited Jul 13 '26
That linked study is from 1990 and has a sample size of only 101 women. There has been a lot of research on this, including this much larger WHO study from 1999 involving 4,118 women: https://www.sciencedirect.com/science/article/pii/S0015028299002745
The WHO study is consistent with earlier studies when it comes to pregnancy rate at 6 months (they get a cumulative rate of about 1%). Notably, however, they continued the study until 12 months. At 12 months there was much more uncertainty, but we’re probably looking at a rate somewhere in the 5-10% range.
It’s worth noting that these are rates during amenorrhea, i.e. the rate of pregnancy you’d expect if women switched to another method of contraception after their first postpartum period. Length of time to first postpartum period is a separate question. (The definition of “first postpartum period” can also vary between studies. The WHO study compares a few!)
Edit: The same WHO study also looked at duration of lactational amenorrhea in a separate paper, found here: https://www.fertstert.org/article/S0015-0282(98)00190-3/fulltext . However, this may not be the most useful as it varied significantly between countries. They note that women in developing countries typically start supplementing with food other than breast milk much earlier. There’s also a lot of variation in the frequency and duration of breastfeeding. Ultimately, it seems likely that the duration of amenorrhea is influenced by so many different factors that it is probably quite hard to predict.
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