Postpartum physiology

- [Voiceover] You know, they say that a woman is never the same after she has a baby, but your body works pretty hard, and it starts working right after the baby is born, to get the body back into its pre-pregnancy state. It usually takes somewhere along six to eight weeks to occur, for most of the organ systems to go back to working the way they did before pregnancy. What happens right after delivery occurs? For some women, something like twenty-five to fifty percent of women, so almost half of all women, start shivering. These postpartum shivers, they usually start within thirty minutes of delivery, and they last anywhere from two minutes long, to being an entire hour long. We're not exactly sure why they occur. We think that it might be related to sudden thermal imbalances from the separation of the placenta. Maybe it's related to certain medications or anesthesia that's used during the delivery, or, perhaps, even, due to bacteria in the blood. We're not exactly sure why they occur, but, in any case, there's no real treatment for them, other than to give the woman a warm blanket. They tend to resolve on their own, so, maybe not as clinically significant, but it's important to know so that you're not startled when you see them or you experience them for the very first time. Starting with the uterus, let's talk about what happens after the baby and the placenta are delivered. Immediately after delivery, the uterus starts to contract. I mean, baby's out, placenta's out, the uterus immediately starts to contract. After a few of those successive contractions, the uterine muscle starts to shorten. Those contractions also help to constrict the blood vessels that are running through the uterine muscle. That helps to control any bleeding that might be going on. When you palpate the uterus, when you feel for the uterus, the uterus should feel more firm and feel more globular than it did in the pregnancy. Within about twenty four hours after delivery, the uterus shrinks down, so you can feel the fundus, which is the top of the uterus, kind of, at the level of the umbilicus, so at the level of the belly button. By one week postpartum, the fundus can be felt halfway between the umbilicus and the pubic symphysis, so, pretty rapid reduction. Then, by two weeks, you can't feel the fundus anymore. Within six to eight weeks, it's returned to its normal size, so, pretty quick reduction back down to its normal size. The shrinking of the uterus back down to its normal size, is affected by a couple of different things. In women who had multiple babies in the past, and in women in whom the delivery of the baby occurred by C-section, rather than by vaginal delivery, the uterus tends to be larger. Compare that with breast-feeding. Breastfeeding tends to cause a quicker reduction in the size of the uterus. A lot of that has to do with a hormone called oxytocin. So there's hormone called oxytocin that's released from the brain. The primary function of oxytocin has nothing to do with the uterus. The primary function of oxytocin is to contract the ducts of the breast, to help release milk. One of the side effects, I guess you could say, of it, is that it also causes the uterus to contract, causing it to shrink at a faster rate. That's why women who breastfeed have a quicker shrinking rate, essentially, of the uterus than women who do not breastfeed. With regards with what's going on on the inside of the uterus, remember that the placenta attaches itself to the decidua basalis. The placenta is attached to the decidua basalis of the uterus. That decidua basalis, that lining of the uterus, is left behind after the placenta separates. It's left behind, and what it does is, it splits up into two different layers. There will be the superficial layer, which is shed, and the deeper layer, which sticks around, and it regenerates a new endometrium. When the bloody desidua sheds, it does so for the first few days following delivery. The woman observes that, she sees it. It's referred to as lochia rubra. The lochia rubra, rubra meaning red, right, so it's red lochia. After that, the vaginal delivery becomes very watery. That's called called lochia serosa. That lochia serosa lasts for about two to three weeks. Ultimately, that vaginal discharge turns more yellow, yellow-white color. Then it's referred to as lochia alba, with alba meaning white. You can see that vaginal discharge, a significant amount of vaginal discharge lasts for about a month following delivery. It's not just the uterus which contracts to become smaller, the cervix and the vagina do the exact same thing. After delivery, the cervix, which is the opening of the uterus through which the baby passes through, as you can probably imagine, is pretty soft and floppy. After delivery, the cervix starts to contract. By one week postpartum, you'll see that it's somewhere less than one inch dilated. The external os, or the external opening of the cervix, actually, never returns to the same shape that it had before pregnancy. Instead of being this small, smooth, circular opening, it becomes a large, sort of, horizontal slit, after childbirth. Similarly, the vagina is very smooth and dilated after delivery. It slowly, very slowly, contracts to shrink down, but, usually, it doesn't reach its pre-pregnancy size. As the swelling reduces, the rugae of the vagina come back, usually within three weeks or so, so the smooth surface is replaced by the typical rugated surface of the vagina. Normally, it's safe to resume sex about three to four weeks postpartum. Finally, with regards to the return of ovulation and the return of menses, that usually occurs within six to eight weeks after delivery in women who don't breastfeed, so that's an important distinction. In women who do not breastfeed, menses and ovulation usually return within six to eight weeks. In women who do breastfeed, however, ovulation and menses don't return for up to six months, during the time the woman is breastfeeding. That's because in order to sustain breastfeeding, the hypothalamus, which is in the brain, has to produce a hormone called prolactin. So the hypothalamus produces this hormone called prolactin, which is really important for stimulating lactation. However, prolactin also inhibits, I guess you can say again, this is one of the side effects of this hormone, prolactin also inhibits sex hormone production, which prevents ovulation from occurring. In fact, in some under-developing countries, breastfeeding is used as a main method of contraception after delivery, after the woman gives birth. Those are some of the changes that occur after the baby is delivered.