Maternal physiology Flashcards
Changes to the uterus in pregnancy
- Hyperplasia - increased weight and height
- Uterine ligaments stretch + hypertrophy
- Right dextro-rotation
- Lower segment
Changes to the cervix, vulva and vagina during pregnancy
Cervix: ¥ Edematous congestion ¥ Eversion of columnar cells ¥ Increased secretion of cervical glands ¥ Mucous plug (operculum)
Vulva - increased vascularity and varicosities
Vagina - increased vascularity and distension at birth
Breast changes in pregnancy
¥ Increased size and vascularity – warm, tense and tender
¥ Increased pigmentation of nipple and areola
¥ Secondary areolar appear - light pigmentation around primary areolar
¥ Montgomery tubercles appear on areolar – dilated sebaceous glands
¥ Colostrum expressed from as early as 16 weeks
Pituitary and endocrine changes in pregnancy
PITUITARY
¥ Anterior pituitary increase in size and activity
¥ Posterior pituitary releases oxytocin at onset of labour and during lactation
THYROID
¥ Increase in size and activity
¥ TBG levels double
¥ Increase in total T3 and total T4 (not free T3/4)
Progesterone changes in pregnancy
¥ Produced by corpus luteum then placenta
¥ Levels rise steadily during pregnancy until output reaches 250mg/day
Progesterone actions in pregnancy
o Relaxation
o Nausea, colon activity reduced, constipation
o Reduced bladder and uteric tone
o Diastolic BP reduced
o Venous dilation and raised temperature
o Anti inflammatory
Oestrogen source, levels and actions in pregnancy
Source
¥ Ovary early, placental and fetal adrenals later
¥ Oestrone and oestradiol produced by placenta
¥ Oestriol produced by placenta and fetal adrenals
Levels
¥ Reaches a maximum of 30-40mg/day
¥ Levels increase up to term
Actions
¥ Induces growth of uterus
¥ Responsible for development of breasts (progesterone too)
¥ Alters chemical constitution of connective tissues
¥ Water retention
¥ Reduced sodium excretion
Urinary changes in renin during pregnancy
INCREASED RENIN ¥ Stimulated by progesterone ¥ Made in placenta ¥ Net excretion of Na+ ¥ Excretion of K+ ¥ Water retention 6-8L ¥ Reduced osmolarity
Implications of urinary changes during pregnancy
¥ Frequency a symptom of pregnancy
¥ Increased UTI (stasis/reflux) – easy to miss
¥ Increased pyelonephritis
¥ Increase in challenges interpreting renal imaging during pregnancy
o Right physiologic hydronephrosis
¥ Increased oedema
o Low oncotic pressure
o Fluid retention
Neural tube defects incidence and types
1/1000 births
- anencephaly
- spinabifida
- encephalocele
Neural tube development
¥ The closure of the neural tube begins in the cervical area (in the middle of the embryo) and spreads from there in the cranial and caudal directions.
¥ Cranial end closes by day 24 and the caudal end by day 26.
¥ If the posterior neuropore does not close, spina bifida occurs.
¥ If the closure of the anterior neuropore fails to take place, anencephaly results.
Risk factors for neural tube defects
2-5% recurrence in subsequent pregnancies
Genetic influences
o Known genetic syndromes (egtrisomy 18)
o Familial clustering
Multiple pregnancies
Environmental agents
- Hyperthermia (saunas, maternal pyrexia)
Nutritional deficiencies
Importance of folate in pregnancy
- Folate deficiency: accumulation of homocysteine – associated with cardiovascular disease risk
- Several gene polymorphisms affect folate metabolism
- These are associated with reduced folate absorption and therefore increased folate needs
- MTHFR (methylene-tetrahydrofolate reductase) gene mutation: affects 8-35% population depending upon ethnicity
- Reduced folate carrier (RFC1) gene
- In the absence of a folate-sufficient diet these mutations are associated with an increased risk of NTDs and conotruncal cardiac anomalies
- Reduces the prevalence of NTD
Recommended folate intake during pregnancy
- Women with no risk factors for NTD: 400 mcg folic acid preconception until 12 weeks gestation
- Women with risk factors (prior NTD, diabetes, antiepileptic medications): 5 mg folic acid
- 5-methyl-tetrahydrofolate (5-MTHF) has been proposed as an alternative to folic acid supplementation.
• 2009: mandatory folic acid fortification in Australia
o 200-300mcg/100gflour
o NTDs predicted to fall 40-70%
Cause of trisomy 21
95% due to non-disjunction