BGDA Practical 12 - Birth
|Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities|
- 1 Introduction
- 2 Childbirth
- 3 Birth Method
- 4 Birth Weights
- 5 Birth Terms
- 6 Additional Information
- 7 Glossary Links
Birth or parturition is a critical stage in development, representing in mammals a transition from direct maternal support of fetal development, physical expulsion and establishment of the newborns own respiratory, circulatory and digestive systems. These notes only cover the biological processes surrounding birth including fetal signaling changes and maternal signaling changes. Note that there is a growing worldwide trend in developed countries toward caesarean section delivery. There are a great number of comprehensive, scientific and general, books and articles that cover birth, childbirth or parturition. The time surrounding birth is known as the perinatal period.
Position of the Uterus and Fetus at Term (Braune, 1877)
- Parturition (Latin, parturitio = "childbirth") describes expelling the fetus, placenta and fetal membranes and is probably initiated by fetus not mother.
- Preterm birth - Risks of preterm birth in abnormal low birth weight (intrauterine growth restriction) and high (large for gestational age) categories are 2- to 3-fold greater than the risk among appropriate-for-gestational-age infants.
- Maternal labor - uterine contractions and dilation of cervix, process under endocrine regulation
- Placenta and fetal membranes - (Latin, secundina = "following") expelled after neonate birth
Uterine Myometrial Changes
- Smooth muscle fibers - hypertrophy not proliferation
- Stretching of myometrium - stimulates spontaneous muscular contraction, during pregnancy progesterone inhibits contraction
- Stimulating contraction - increased estrogen levels (placental secretion sensitizes smooth muscle), increased oxytocin levels (fetal oxytocin release- force and frequency of contraction), fetal pituitary prostaglandin production (estrogen and oxytocin stimulate endometrial production of prostaglandin)
- mainly shown in other species parturition occurs in peaceful undisturbed surroundings, stress may have an inhibitory effect on oxytocin release
- Most human births occur at night (peak at 3 am) diurnal rhythm influence
|Stage 1||Dilatation||7 to 12 hours
longer for first child
|Uterine contractions 10 minutes apart, function to dilate cervix fetal membranes rupture releasing amnion.|
|Stage 2||Expulsion||20 to 50 minutes||Uterine contractions 2 to 3 minutes apart, function to push fetus through cervix and vagina.|
|Stage 3||Placental||15 minutes||Uterine contractions following child delivery expel placenta. Haematoma separates placenta from uterine wall, separation occurs at spongy layer of decidua basalis.|
|Stage 4||Recovery||2+ hours||Uterine contractions continue and myometrial contraction closes spiral arteries, also begins to reduce uterine volume.|
| The birth of a child in an “open” MRI (magnetic resonance imaging) scanner that allows a mother-to-be to fit fully into the machine.
Method of Birth (Australia, 2007)
Birth - Caesarean
The rate of caesarean delivery (c-section or C/S) compared to normal vaginal birth is variable between countries (12-25%) and increasing, particularly in older women. There are a number of different explanations as to why this is occuring, including maternal or fetal complications of either development or delivery. The World Health Organization (WHO) recommended rate (10 - 15%).
Links: Birth - Caesarean Delivery
|Birth weight (grams)||less 500||500 – 999||1,000 – 1,499||1,500 – 1,999||2,000 – 2,499||2,500 – 2,999||3,000 – 3,499||3,500 – 3,999||4,000 – 4,499||4,500 – 4,999||5,000 or more|
The primary causes of VLBW are premature birth (born <37 weeks gestation, and often <30 weeks) and intrauterine growth restriction (IUGR), usually due to problems with placenta, maternal health, or to birth defects. Many VLBW babies with IUGR are preterm and thus are both physically small and physiologically immature.
Birthweight (Australia, 2007)
- 92.1% of liveborn babies had a birthweight in the range 2,500–4,499 grams
- average birthweight was 3,374 grams
- 17,976 (6.2%) low birthweight (weighing less than 2,500 grams)
- 2,956 (1.0%) very low birthweight (weighing less than 1,500 grams)
- 1,288 (0.4%) extremely low birthweight (weighing less than 1,000 grams)
Data: Australia’s mothers and babies 2007 AIHW Perinatal statistics series no. 23
|Practical 12: Embryo to Fetus | Second Trimester | Third Trimester | Birth | Neonatal | Abnormalities|
- amniotomy - birth medical procedure thought to speed labor, where the amniotic sac is artificially ruptured using a tool (amniohook).
- birth - (parturition, partus, childbirth, labour, delivery). expulsion of the foetus from the uterus. (More? Birth)
- birth weight - (birth-weight) the weight of the neonate measured as soon as possible after birth. (More? Birth Weight)
- Bishop score - (Bishop's score) A clinical test prior to birth named after the obstetrician/gynaecologist Edward H. Bishop (1913-1995) who published a 1964 paper "Pelvic Scoring For Elective Induction". (More? PMID 14199536)
- breech - fetal buttocks presented first and can also occur in different forms depending on presentation (complete breech, frank breech, footing breech, knee breech).
- decidual activation - increased uterine proteolysis and extracellular matrix degradation.
- dilatation - opening of the cervix in preparation for birth (expressed in centimetres).
- effacement - shortening or thinning of the cervix, in preparation for birth.
- early cord clamping - placental cord clamping carried out in the first 60 seconds after birth.
- forceps - mechanical "plier-like" tool used on fetal head to aid birth.
- induction of labour - clinical procedure where labour starts artificially by using a membrane sweep, pessary or hormone drip.
- instrumental birth - birth process where the use of clinical instruments is required.
- labor - the maternal physiological process of birth. (More? Birth)
- macrosomia - clinical description for a fetus that is too large, condition increases steadily with advancing gestational age and defined by a variety of birthweights. In pregnant women anywhere between 2 - 15% have birth weights of greater than 4000 grams (4 Kg, 8 lb 13 oz). (More? Macrosomia)
- membrane rupture - breaking of the amniotic membrane and release of amniotic fluid (water breaking).
- morbidity - (Latin, morbidus = "sick" or "unhealthy") refers to a diseased state, disability, or poor health due to any cause.
- necrotising enterocolitis - clinical condition mainly seen in preterm infants, where portions of the bowel undergo necrosis.
- neonatal - the early postnatal period relating to the birth, it includes the period up to 4 weeks after birth.
- obstetric fistula - abnormal connection between the vagina and rectum or bladder caused by a prolonged obstructed labor.
- perinatal - the early postnatal period relating to the birth, statistically it includes the period up to 7 days after birth.
- presentation - how the fetus is situated in the uterus.
- presenting part - part of fetus body that is closest to the cervix.
- preterm birth - birth of an infant before GA 37 weeks of pregnancy. (More? Birth - Preterm)
- second stage of labour - passage of the baby through the birth canal into the outside world.
- stillbirth - death of a baby after GA 24 weeks of pregnancy but before birth.
- tachycardia - rapid fetal heart rate (greater than 160 beats per minute) for the term fetus, usually determined by fetal monitoring.
- third stage of labour - interval from the birth of the baby to the expulsion of the placenta and membranes.
- tocolytic - a drug used to prevent or lessen uterine contractions.
- uterotonic - drug used to induce uterine contractions.
- vacuum extractor - (ventouse) rubber or metal suction cap device used on fetal head to aid birth.
- vertex presentation - (cephalic presentation) where the fetus head is the presenting part, most common and safest birth position.
|Other Terms Lists|
|Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Respiratory | Spermatozoa | Ultrasound | Vision | Historic | Glossary|
|Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.|
- Birth Links: Introduction | Lecture - Birth | Caesarean | Preterm | Birth Weight | Birth Statistics | Australian Birth Data | Developmental Origins of Health and Disease | Macrosomia | Neonatal Diagnosis | Apgar test | Guthrie test | Neonatal Development | Stillbirth and Perinatal Death | ICD-10 Perinatal Period | Category:Birth
Historic Birth Models
About The Models - a series of models commissioned by Giuseppe Galletti (? - 1819) currently held in the Institute and Museum of the History of Science (Italy) Istituto e Museo di Storia della Scienza (IMSS). Giuseppe Galletti and others used terracotta and wax models that he had commissioned in Florence between 1770 and 1775 to train surgeons and midwives.
|Year||< 34 weeks %||34-36 weeks %||total preterm %|
- "One of the major success stories of modern obstetrics in high-income countries in the last 5 decades is the reduction of stillbirths from rates as high as 50 per 1000 births to about 5 per 1000 births today. Fetal mortality associated with obstructed labour, asphyxia, hypertension, diabetes, Rh disease, placental abruption, post-term pregnancies and infections such as syphilis all have declined. Much of this success has occurred in term births in the intrapartum period so that most stillbirths in high-income countries now occur in the antepartum period and are pre-term."
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Cite this page: Hill, M.A. 2018 Embryology BGDA Practical 12 - Birth. Retrieved January 21, 2018, from https://embryology.med.unsw.edu.au/embryology/index.php/BGDA_Practical_12_-_Birth
- © Dr Mark Hill 2018, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G