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
Techniques for diagnosing trisomy 21
o Prenatal diagnosis based on maternal age
(amniocentesis/CVS)
o Combined First Trimester Screening (80-90% detection rate)
o Second Trimester Screening (60-70% detection rate)
o Non-invasive Prenatal Testing (99.5% detection rate)
Cardiovascular defects
Hypoplastic left heart syndrome
Tetralogy of fallot
Transposition of great arteries
Medications and birth defects - category A
Drugs taken by large number of pregnant/women of childbearing age
- thyroxine, folic acid
Medications and birth defects - category B1/2/3
1) Drugs taken by limited number of pregnant women
No increase in harmful effects/malformations
- azithromycin, cetaxime
2) Drugs taken by limited number of pregnant women, studies in animals are lacking but no evidence of harm
- vaccines
3)Drugs taken by limited number of pregnant women
Evidence of increased risk in animals, unsure in humans
Medications and birth defects - category C
• Drugs which, owing to their pharmacological effects, have caused or may be suspected of causing, harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible.
Example: naproxen, nifedipine, oxprenolol, metformin
Medications and birth defects - category D
- Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects.
- Example: phenytoin, ramipril
Category X
- Drugs which have such a high risk of causing permanent damage to the fetus that they should not be used in pregnancy or when there is a possibility of pregnancy
- Example: methotrexate, retinoic acid, thalidomide,
Benefits of breastfeeding to the mother
• Recoveryfromchildbirth • Body weight loss • Suppression of maternal fertility • Cholesterol clearance • Diabetics – glucose control • Breast & ovarian cancer less • Self esteem
Benefits of breast feeding to the child
- ‘Gold Standard’ infant food
- Facilitatesgrowthand development
- Protects against illness
