[Note: This article is being published in draft form for use in an active research study. Its contents may be adjusted as we recieve feedback from collaborating health care professionals.]
Post-partum, the human body undergoes several changes.
Uterus, Cervix, and Vagina
The process of reproductive organs returning to their prepregnant state is known as involution. The uterus begins to contract shortly after delivery to minimize blood loss, which can result in abdominal cramping and pain. Immediately postpartum, the uterus typically weighs 1000 grams; at one week postpartum, it has reduced to about 500 grams, and at 6 weeks postpartum, it weighs about 50 grams. After the initial contractions reduce the size of the uterus, involution begins to include autolysis and infarction of uterine blood vessels,1-3 aided by hormonal shifts that lead to an increase in collagenase and proteolytic enzyme activities.4 The endometrium is usually restored to prepregnancy physiology within 2-3 weeks.
Lochia - the vaginal discharge originating from the uterus, cervix, and vagina - is red immediately postpartum for 1-4 days, changing to yellowish or pale brown for another 5-10 days, then whitish for another 10-14 days. Lochia can last for up to 5 weeks postpartum. Longer periods of darker colors or foul odors should prompt medical evaluation and could indicate uterine subinvolution or infection.5-7
The cervix and vagina may be edematous and bruised early in the postpartum period, usually turning to normal within days to 2 weeks. The vaginal epithelium is atrophic immediately postpartum, but rugae return to the vagina usually be 3 weeks postpartum if the mother is not breastfeeding. Normal vaginal epithelium is usually restored within 6-10 weeks but can take longer if the mother is breastfeeding.8
If the birthing mother required an episiotomy or suffered a laceration, she will experience discomfort in the perineal area for a few days until healing occurs and stitches are removed. This can be especially uncomfortable during urination.
Lactation and Breasts
Colostrum, the breast secretion rich in protein, vitamins, immunoglobulins, lactoferrin, and other humoral factors, begins to secrete within minutes to hours after the delivery. Milk secretion starts on the third or fourth day postpartum and often flows with visual stimuli such as seeing the baby, a reflex known as “milk let down.” This reflex can be inhibited by pain, anxiety, depression, or breast engorgement. Lactation increases in step with the baby’s demands, and requires about 700 kcal/day, which draws on fat stored during pregnancy. Therefore, breastfeeding often leads to natural weight loss to allow the mother to approach her prepregnancy weight. Nipples can become sore due to nursing, and mastitis can occur, especially if milk is not expressed sufficiently.9,10
Not related to breastfeeding is change in the breast tissue postpartum that often results in softer, sagging breasts. This change is often permanent.
Menstruation
Periods return depending on lactation. Without breastfeeding, menstruation typically returns 6-8 weeks postpartum. In breastfeeding mothers, periods often return starting at 4-5 months but sometimes as late as 24 months postpartum. Although anovulation is a natural contraceptive, it is difficult to predict when menstruation will start again, thus use of contraceptive strategies other than breast feeding are advised if the mother wishes to control when she gets pregnant again. Non-lactating mothers are advised to start using contraceptives 3 weeks postpartum and lactating mothers starting 3 months postpartum.
Kidneys and Urination
Six to 8 liters of total body water shifts from the extravascular to the intravascular space postpartum, and due to increases in atrial natriuretic peptide, the 950 mEq of excess sodium along with water are excreted through a diuresis that typically last for 2 weeks postpartum.11 Lactosuria is not uncommon on the 3rd or 4th day after onset of lactation.
Hematologic System
Pregnancy is a hypercoagulable state, a physiologic response that helps to minimize blood loss during delivery. This state also increases risk for pathologic embolism, an unfortunate complication in pregnancy that lasts 8-12 weeks into the postpartum period as the hematologic system returns to the prepregnancy state.12,13 Risks for thromboembolism are approximately ten times higher during pregnancy and twenty times higher in the early postpartum period, compared to nonpregnant states.14,15
Hematocrit also undergoes shifts in the early postpartum period. It may drop due to blood lost during the delivery, then rises as fluid shifts occur and plasma volume decreases.16 Complete normalcy in hemoglobin may not occur for 4-6 months post-delivery.17
Gastrointestinal System
Postpartum flatulence or constipation are common, resulting from intestinal ileus as a response to the pain of delivery and placental relaxin.18,19 Loss of fluid and laxity of the abdominal wall may contribute. Postpartum progesterone also decreases gastrointestinal transit time. Hemorrhoids are very common during pregnancy due to elevated intraabdominal pressure from the gravid uterus; these usually resolve in 6-8 weeks.
Skin and Skeletal System
Up to 90% of pregnant mothers experience hyperpigmentation, with unclear physiology; theories include hypersensitivity of melanocytes to estrogen, progesterone, and endorphin during pregnancy. These changes usually resolve 6-8 weeks post-delivery.20,21
Stretch marks occur due to the stretching of the skin during pregnancy, and these usually do not disappear entirely, although they may become paler over time.22
The lax abdominal muscles following delivery take 6-8 weeks to return to their prepregnancy tone and elasticity. This often results in a slightly protruding abdomen early in the postpartum period that my not entirely return to the pre-pregnancy appearance, often called “Mommy pooch”.
Night sweats may occur in the early postpartum period due to hormonal shifts. These usually do not last more than a few days.
Hair loss in the early postpartum is common, also due to hormonal shifts. This can be distressing to the young person; hair growth usually returns to normal within a few months.
Greater blood volume and intraabdominal pressure during pregnancy can lead to varicose veins. These may or may not resolve after the postpartum period. Greater pressure and the process of giving birth may also slightly widen hips, which usually does not resolve. Many women also report that their feet grow slightly, sometimes asymmetrically. Larger feet also do not always resolve.
Mental Health
Mood swings in the early postpartum period are very common and are thought to be attributable to hormonal shifts. About half of birthing parents experience so-called “baby blues”, or mood swings.23 Mothers who have a history of depression or dysthymia, greater number of lifetime pregnancies, and family history of postpartum depression all increase risk for mood swings postpartum. Despite the common nature of this disorder, its pathophysiology is poorly understood and hormonal changes are thought to be the primary reason.
Mood swings increase the risk for frank postpartum depression, interfering with baby bonding and self- and baby care. Postpartum mood swings usually begin within 2-3 days of delivery and dissipate within 2 weeks.23 In contrast, postpartum depression lasts for longer than 2 weeks and include the usual criteria for depression: emotional lability, dysphoria, irritability, anxiety, insomnia, appetite changes.
Postpartum mood swings increase the risk of postpartum depression by 4-11 times. Between 13-19% of mothers experience postpartum depression, prevalence estimates that predated the COVID-19 pandemic that was associated with substantial increases in population prevalence of anxiety and depression.24 Postpartum depression is a common reason for postpartum mortality; a 2020 CDC report estimated that mental health problems were the leading cause of pregnancy-related deaths.25
Hormonal changes have effects on the brain. So-called “Mommy brain” is a phenomenon in which empathy and maternal attachment increases, with changes observed for 2 years following delivery (but possibly lasting longer, since the study ended with 2 years of observation). A 2024 study confirmed earlier reports of gray matter thinning and increases in white matter microstructural integrity that was global across the brain at 2 years following delivery, the end of the study’s observation period.26,27
References
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- Mulic-Lutvica A, Bekuretsion M, Bakos O, Axelsson O. Ultrasonic evaluation of the uterus and uterine cavity after normal, vaginal delivery. Ultrasound Obstet Gynecol. 2001;18(5):491-498.
- Sokol ER, Casele H, Haney EI. Ultrasound examination of the postpartum uterus: what is normal? J Matern Fetal Neonatal Med. 2004;15(2):95-99.
- Cyganek A, Wyczalkowska-Tomasik A, Jarmuzek P, et al. Activity of Proteolytic Enzymes and Level of Cystatin C in the Peripartum Period. Biomed Res Int. 2016;2016:7065821.
- Sherman D, Lurie S, Frenkel E, Kurzweil Y, Bukovsky I, Arieli S. Characteristics of normal lochia. Am J Perinatol. 1999;16(8):399-402.
- Oppenheimer LW, Sherriff EA, Goodman JD, Shah D, James CE. The duration of lochia. Br J Obstet Gynaecol. 1986;93(7):754-757.
- Chi C, Bapir M, Lee CA, Kadir RA. Puerperal loss (lochia) in women with or without inherited bleeding disorders. Am J Obstet Gynecol. 2010;203(1):56.e51-55.
- Mc LH. The involution of the cervix. Br Med J. 1952;1(4754):347-352.
- Crowley WR. Neuroendocrine regulation of lactation and milk production. Compr Physiol. 2015;5(1):255-291.
- The World Health Organization Multinational Study of Breast-feeding and Lactational Amenorrhea. II. Factors associated with the length of amenorrhea. World Health Organization Task Force on Methods for the Natural Regulation of Fertility. Fertil Steril. 1998;70(3):461-471.
- Ogueh O, Clough A, Hancock M, Johnson MR. A longitudinal study of the control of renal and uterine hemodynamic changes of pregnancy. Hypertens Pregnancy. 2011;30(3):243-259.
- de Boer K, ten Cate JW, Sturk A, Borm JJ, Treffers PE. Enhanced thrombin generation in normal and hypertensive pregnancy. Am J Obstet Gynecol. 1989;160(1):95-100.
- Eichinger S. D-dimer testing in pregnancy. Pathophysiol Haemost Thromb. 2003;33(5-6):327-329.
- Jackson E, Curtis KM, Gaffield ME. Risk of venous thromboembolism during the postpartum period: a systematic review. Obstet Gynecol. 2011;117(3):691-703.
- Tepper NK, Boulet SL, Whiteman MK, et al. Postpartum venous thromboembolism: incidence and risk factors. Obstet Gynecol. 2014;123(5):987-996.
- Nicol B, Croughan-Minihane M, Kilpatrick SJ. Lack of value of routine postpartum hematocrit determination after vaginal delivery. Obstet Gynecol. 1997;90(4 Pt 1):514-518.
- Taylor DJ, Lind T. Red cell mass during and after normal pregnancy. Br J Obstet Gynaecol. 1979;86(5):364-370.
- Glazener CM, Abdalla M, Stroud P, Naji S, Templeton A, Russell IT. Postnatal maternal morbidity: extent, causes, prevention and treatment. Br J Obstet Gynaecol. 1995;102(4):282-287.
- Shin GH, Toto EL, Schey R. Pregnancy and postpartum bowel changes: constipation and fecal incontinence. Am J Gastroenterol. 2015;110(4):521-529; quiz 530.
- Bieber AK, Martires KJ, Stein JA, Grant-Kels JM, Driscoll MS, Pomeranz MK. Pigmentation and Pregnancy: Knowing What Is Normal. Obstet Gynecol. 2017;129(1):168-173.
- Motosko CC, Bieber AK, Pomeranz MK, Stein JA, Martires KJ. Physiologic changes of pregnancy: A review of the literature. Int J Womens Dermatol. 2017;3(4):219-224.
- Tyler KH. Physiological skin changes during pregnancy. Clin Obstet Gynecol. 2015;58(1):119-124.
- Howard LM, Molyneaux E, Dennis CL, Rochat T, Stein A, Milgrom J. Non-psychotic mental disorders in the perinatal period. Lancet (London, England). 2014;384(9956):1775-1788.
- O'Hara MW, McCabe JE. Postpartum depression: current status and future directions. Annu Rev Clin Psychol. 2013;9:379-407.
- Trost S, Busacker A, Leonard M, et al. Pregnancy-Related Deaths: Data from Maternal Mortality Review Committees in 38 U.S. States, 2020. In: U.S. Department of Health and Human Services Centers for Disease Control and Prevention; 2024.
- Hoekzema E, Barba-Müller E, Pozzobon C, et al. Pregnancy leads to long-lasting changes in human brain structure. Nat Neurosci. 2017;20(2):287-296.
- Pritschet L, Taylor CM, Cossio D, et al. Neuroanatomical changes observed over the course of a human pregnancy. bioRxiv. 2024.
