Z.A.
It's true for some people, but not for others.
Just as it's true that some babies won't nurse after taking a bottle, some just need to get into the swing of it (takes a few weeks), some go back and forth with no problem at all, and some won't touch take milk from anything that's not a breast.
I've known a woman who pumped for 4.5 years after "weaning", because she was a donor...and then there's me...who couldn't pump to save her own life (but my son at 5 days old would take more than 20 oz PER feeding), and I "wet nursed" for a friend while she had to have emergency surgery.
We're all a little bit different, but there are some generalities. Many many many women continue to nurse after starting their period (I got mine back a month after my son was born, fertile Myrtile, that's me)...but some women don't even get their period back until after they quit nursing. We're talking up to two years of no period.
My suspicion is this:
1) You've been pumping since day 5...so you'll in all likelyhood be able to pump for the next two years if you so choose. You and your body have the swing of it, all these months down the road. That's quite a bit different from the mum who nursed for the first 6 months, then started pumping so she could go back to work. Or even mum's who nurse part time and pump part time.
2) Having your period means you're using extra energy (and so does nursing)...so if you're feeling pms-like, keep up on your iron/folates/calories/etc & drink WATER. A lot of PMS symptoms are actually dehydration symptoms.
3) We've finally gotten some warmer weather. So you're probably a touch dehydrated. Oops...there we go again. Water water water.
4) The amount and composition of our milk changes as our baby ages. I don't know if you're doing the saliva trick (putting a little baby drool on the suction part of the pump), but if you are, your body MAY just be reacting to a change in her needs.
ALSO
The three single most common causes for decrease in supply when demand is still high:
- Dieting
- Stress
- Dehydration
How are you doing on those three? (HA, Don't you love it when people tell us to eliminate the stress? Like helllloooo I'm a mum here. I coexist with stress. I'm the goodyear tire commercial where I'm pulling my wee one off the wall while continuing a detail oriented conversation, while at the same time thinking of the other 6 things I need to get done before naptime. <grinning> Stress. Ha! Why don't they say & give us tips and trick from how to eliminate FEAR & WORRY from our lives??)
Anyhow...the la leche league has tons of advice...but remember, if what you're doing is working...it's working. You don't need to be afraid that what you're doing will stop working like magic just because it doesn't work at all for some people. Drink a lot of water, eat a snack, relax. (And...old trick still commonly used...if you're really stressed out try drinking a beer right before you pump -it doesn't get into the milk that way, not enough time-. Just remember you'll have to drink more water later to make up for it.)