Postpartum Physiologic Changes

Postpartum Physiologic Changes

• Postpartum period: interval between birth and return of reproductive organs to a nonpregnant state (AKA puerperium, last 6 weeks).

Reproductive Systems and Associated Structures

Uterus

• Involution: Uterus returns to nonpregnant state after childbirth, begins immediately after placenta expulsion with uterine smooth muscle contractions.
• At end of third stage of labor, uterus weighs ~1000g, midline, ~2 cm below umbilicus.
• Within 12 hours, uterus rises ~1cm above umbilicus.
• By 24 hours, uterus is the same size as at 20 weeks gestation.
• Daily, fundus descends 1-2 cm.
• By 6th day, fundus is halfway between umbilicus and symphysis pubis.
• After 2 weeks, uterus is not palpable abdominally.
• By one week, uterus weighs ~500g.
• By 4 weeks, uterus weighs ~100g, and has returned to nonpregnant size/location.
• Subinvolution: Failure of uterus to return to nonpregnant state, commonly due to retained placental fragments or infection. This is caused by ineffective contractions.

Contractions

• Postpartum hemostasis achieved by uterine contractions.
• Initial contractions are intense, but they decrease in intensity over the first 1-2 hours and may become uncoordinated.
• Pitocin (oxytocin) may be given IV or IM to help with contractions and/or breastfeeding can also stimulate oxytocin release.
• Afterpains: Periodic relaxation and vigorous uterine contractions in subsequent pregnancies cause cramping. This typically lasts for 3-7 days.

Placental Site

• Factors that intensify afterpains: uterine overdistension, breastfeeding, Pitocin.
• Vascular restriction and thromboses reduce the placental site.
• Endometrial regeneration begins at day 3 and is complete by week 3.
• Regeneration of the placenta site is complete by week 6.

Lochia

• Blood discharge from the uterus after childbirth.
• Classification based on color and characteristics (rubra, serosa, alba) and duration; typically lasts 4-6 weeks.

Cervix

• Soft immediately after birth, and protrudes into the vagina.
• 12-18 hours after birth, cervix shortens and becomes firmer.
• 2-3 days after birth, cervix is shortened, firm, and it regains its original shape.
• 1 week after birth, the cervical os is 1 cm in size.
• external os may be a jagged slit (fish-mouth) shape.

Ovaries

• Ovulation may resume as early as 27 days postpartum in non-lactating women.
• Lactating women may suppress ovulation, but ovulation may return within 6 months.
• First menstruation may be heavier than normal.
• Returns to normal cycles in 3-4 postpartum months.

Vagina and Perineum

• Vaginal mucosa thinness and loss of rugae (folds) may occur due to estrogen decrease after pregnancy.

Breasts

• Decrease in placental hormones may stimulate breast development.
• Colostrum: Early milk, clear yellow fluid, produced during the first 24 hours postpartum.
• Becomes fuller and heavier as colostrum transitions to mature milk in 72-96 hours.
• Breast tissue may feel lumpy (nodular) or shift in position due to milk production.
• Engorgement: Increased blood and lymphatic fluid in breasts may lead to hard, uncomfortable breasts. This may only last for 24-48 hours.

Cardiac System

• Blood volume averages 300-500 mL for vaginal delivery, and 500-1000 mL for C-section.
• Plasma volume decreases within a few days of birth due to diuresis, but returns to pre-pregnancy levels within 3 days.
• Cardiac output increases by 60-80% after birth, then returns to pre-labor values within 1 hour.
• CO decreases by 30% at 2 weeks and returns to normal by weeks 6-8.

Vital Signs (Page 420)

• HR increase initially, then decreases to 40-50 bpm.
• BP may be slightly elevated initially.

Respiratory System

• Intrabdominal pressure decreases.
• Rib cage elasticity returns gradually.
• Costal angle (angle between ribs) may take time to return to pre-pregnancy sizes.
• The partial pressure of carbon dioxide (PaCO2) may decrease due to changes in progesterone levels.

Endocrine System

• Estrogen and Progesterone levels drop considerably after childbirth.
• HCG disappears fairly quickly (within 3-4 weeks).
• Pituitary hormones (e.g., prolactin) increase in those breastfeeding to promote milk production.
• Oxytocin release with breastfeeding.

Urinary System

• Renal function returns to normal by 8 weeks.
• Pelvic organs (ureters, renal pelvis) may take up to 6 weeks to recover from pregnancy-related changes.
• Risk of UTI may be increased.

GI System

• Bowel movements may be delayed for 2-3 days due to slowed peristalsis.

Integument

• Melasma, hyperpigmentation of areolae and linea nigra may not regress completely.
• Striae gravidarum may fade (stretch marks from pregnancy).
• Vascular abnormalities may regress due to hormonal changes (e.g. angiomata, palmar erythema).

Musculoskeletal

• Back pain often resolves in a few weeks or months.
• Joints stabilize by 6-8 weeks.
• Shoe size may increase.

Neurologic

• Headaches or other neurological issues may occur in the immediate postpartum period.
• Relief of carpal tunnel symptoms may occur due to diuresis.
• Nasal stuffiness, tinnitus, and laryngeal changes resolve shortly after birth.

Immune

• Exact time for immune system recovery is unclear.
• Autoimmune conditions (like multiple sclerosis or lupus) may exacerbate.