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Obstetrics (from the Latin obstare, "to stand by") is the surgical specialty dealing with the care of women and their children during pregnancy, childbirth and postnatal. Midwifery is the non-medical equivalent. Veterinary obstetrics is the same concept for veterinary medicine.

Antenatal care

In obstetric practice, an obstetrician or midwife sees a pregnant woman on a regular basis to check the progress of the pregnancy, to verify the absence of ex-novo disease, to monitor the state of preexisting disease and its possible effect on the ongoing pregnancy. A woman's schedule of antenatal appointment varies according to the presence of risk factors, such as diabetes, and local resources.

Image:Baby-06.jpg|3D ultrasound of fetus (about 14 weeks gestational age)Image:Sucking his thumb and waving.jpg|Fetus at 17 weeksImage:3dultrasound 20 weeks.jpg|Fetus at 20 weeks


Some of the clinically and statistically more important risk factors that must be systematically excluded, especially in advancing pregnancy, are pre-eclampsia, abnormal placentation, abnormal fetal presentation and intrauterine growth restriction. For example, to identify pre-eclampsia, blood-pressure and albuminuria (level of urine protein) are checked at every opportunity.

Placenta praevia must be excluded (PP = low lying placenta that, at least partially, obstructs the birth canal and therefore warrants elective caesarean delivery); this can only be achieved with the use of an ultrasound scan. However, early placenta praevia is not alarming; this is because as the uterus grows along the pregnancy, the placenta may still move away. A placenta praevia is of clinical significance as from the 28th week of gestation. The current management includes a caesarean section. The type of caesarean section is determined by the position (anterior or posterior) of the placenta.

In late pregnancy fetal presentation must be established: cephalic presentation (head first) is the norm but the fetus may present feet-first or buttocks-first (breech), side-on (transverse), or at an angle (oblique presentation).

Intrauterine growth restriction is a general designation where the fetus is smaller than expected when compared to its gestational age (in this case, fetal growth parameters show a tendency to drop off from the 50th percentile eventually falling below the 10th percentile, when plotted on a fetal growth chart). Causes can be intrinsic (to the fetus) or extrinsic (maternal or placental problems).

Maternal Change

Cardiovascular

The woman is the sole provider of nourishment for the embryo and later, the fetus, and so her plasma and blood volume slowly increase by 40-50% over the course of the pregnancy to accommodate the changes. This results in overall vasodilation, an increase in heart rate (15 beats/min more than usual), stroke volume, and cardiac output. Cardiac output increases by about 50%, mostly during the first trimester. The systemic vascular resistance also drops due to the smooth muscle relaxation caused by elevated progesterone, leading to a fall in blood pressure. Diastolic blood pressure consequently decreases between 12–26 weeks, and increases again to pre-pregnancy levels by 36 weeks. If the blood pressure becomes abnormally high, the woman should be investigated for pre-eclampsia and other causes of hypertension.

Endocrine

Pregnant women experience adjustments in their endocrine system. These adjustments include an increase in her estrogen levels; which is mainly produced by the placenta and is associated with fetal well–being. Women also experience increased human chorionic gonadotropin (β-hCG); which is produced by the placenta. This maintains progesterone production by the corpus luteum. Additionally, human placental lactogen (hPL) is produced by the placenta, ensuring nutrient supply to the fetus. This also causes lipolysis and is an insulin antagonist, which is a diabetogenic effect.

Additionally, there is increased prolactin, increased alkaline phosphatase, and increased progesterone production, first by corpus luteum and later by the placenta, whose main course of action is to relax smooth muscle.

Gastrointestinal

During pregnancy, woman can experience nausea and vomiting (morning sickness); which may be due to elevated B-hCG and should resolve by 14 to 16 weeks. Additionally, there is prolonged gastric empty time, decreased gastroesophageal sphincter tone, which can lead to acid reflux, and decreased colonic motility, which leads to increased water absorption and constipation.

Hematology

During pregnancy the plasma volume increases by 50% and the red blood cell volume increases only by 20-30%. Consequently, the hematocrit decreases on lab value, however this is not a true decrease in hematocrit, but rather due to the dilution. The white blood cell count increases and may peak at over 20 mg/mL in stressful conditions. Conversely, there is a decrease in platelet concentration to a minimal normal values of 100-150 mil/mL.

A pregnant woman will also become hypercoagulable, leading to increased risk for developing blood clots and embolisms, due to increased liver production of coagulation factors, mainly fibrinogen and factor VIII (this hypercoagulable state along with the decreased ambulation causes an increased risk of both DVT and PE). Women are at highest risk for developing clots, or thrombi, during the weeks following labor. Clots usually develop in the left leg or the left iliac venous system. The left side is most afflicted because the left iliac vein is crossed by the right iliac artery. The increased flow in the right iliac artery after birth compresses the left iliac vein leading to an increased risk for thrombosis (clotting) which is exacerbated by the aforementioned lack of ambulation following delivery. Both underlying thrombophilia and cesarean section can further increase these risks.

Edema, or swelling, of the feet is common during pregnancy, partly because the enlarging uterus compresses veins and lymphatic drainage from the legs.

Metabolism

During pregnancy, both protein metabolism and carbohydrate metabolism are affected. One kilogram of extra protein is deposited, with half going to the fetus and placenta, and another half going to uterine contractile proteins, breast glandular tissue, plasma protein, and hemoglobin.

Neurophysiologic

During pregnancy, the woman undergoes many physiological changes, which are entirely normal, including cardiovascular, hematologic, metabolic, renal and respiratory changes that become very important in the event of complications. The body must change its physiological and homeostatic mechanisms in pregnancy to ensure the fetus is provided for. Increases in blood sugar, breathing and cardiac output are all required. Levels of progesterone and oestrogens rise continually throughout pregnancy, suppressing the hypothalamic axis and subsequently the menstrual cycle. The woman and the placenta also produce many hormones.

Prolactin levels increase due to maternal Pituitary gland enlargement by 50%. This mediates a change in the structure of the Mammary gland from ductal to lobular-alveolar. Parathyroid hormone is increased due to increases of calcium uptake in the gut and reabsorption by the kidney. Adrenal hormones such as cortisol and aldosterone also increase.

Placental lactogen is produced by the placenta and stimulates lipolysis and fatty acid metabolism by the woman, conserving blood glucose for use by the fetus. It can also decrease maternal tissue sensitivity to insulin, resulting in gestational diabetes

Nutrition

Nutritionally, pregnant women require a caloric increase caloric of 300 kcal/day and an increase in protein to 70 or 75 g/day. There is also an increased folate requirement from 0.4 to 0.8 mg/day (important in preventing neural tube defects). On average, a weight gain of is experienced.

All patients are advised to take prenatal vitamins to compensate for the increased nutritional requirements. The use of Omega 3 fatty acids supports mental and visual development of infants. Choline supplementation of research mammals supports mental development that lasts throughout life.

Renal

A pregnant woman may experience an increase in kidney and ureter size. There is also an increase in the glomerular filtration rate (GFR) by 50%, which subsides around 20 weeks postpartum. Plasma sodium does not change because this is offset by the increase in GFR. Additionally, there is decreased blood urea nitrogen (BUN) and creatinine, and glucosuria (due to saturated tubular reabsorption), persistent glucosuria may suggest gestational diabetes, and increased renin-angiotensin system, causing increased aldosterone levels.

Pulmonary

Changes in pulmonary activity for pregnant woman can include increased tidal volume (30-40%), decreased total lung capacity (TLC) by 5% due to elevation of diaphragm from uteral compression, decreased expiratory reserve volume, and increased minute ventilation (30-40%) which causes a decrease in PaCO2 and a compensated respiratory alkalosis

All of these changes can contribute to the dyspnea (shortness of breath) that a pregnant woman may experience.

Other

Other conditions that can be encountered include:
  • Lower back pain due to a shift in gravity
  • Increased estrogen can cause spider angiomata and palmar erythema
  • Increase melanocyte-stimulating hormone (MSH) can cause hyperpigmentation of nipples, umbilicus, abdominal midline (linea nigra), perineum, and face (melasma or chloasma)


Prenatal care

Prenatal care is important in screening for various complications of pregnancy. This includes routine office visits with physical exams and routine lab tests:

First trimester

genetic screening for downs syndrome (trisomy 21) and trisomy 18the national standard in the United States is rapidly evolving away from the AFP-Quad screen for downs syndrome- done typically in the second trimester at 16–18 weeks. The newer integrated screen (formerly called F.A.S.T.E.R for First And Second Trimester Early Results) can be done at 10 plus weeks to 13 plus weeks with an ultrasound of the fetal neck (thick skin is bad) and two chemicals (analytes) Papp-a and bhcg (pregnancy hormone level itself). It gives an accurate risk profile very early. There is then a second blood screen at 15 to 20 weeks which refines the risk more. The cost is higher than an afp-quad screen due to the ultrasound and second blood test but it is quoted to have a 92% pick up rate.

Second trimester

  • MSAFP/quad. screen (four simultaneous blood tests) (maternal serum alpha-fetoprotein; inhibin; estriol; bhcg or free bhcg) - elevations, low numbers or odd patterns correlate with neural tube defect risk and increased risks of trisomy 18 or trisomy 21
  • Ultrasound either abdominal or trannsvaginal to assess cervix, placenta, fluid and baby
  • Amniocentesis is the national standard for women over 35 or who reach 35 by mid pregnancy or who are at increased risk by family history or prior birth history


Third trimester

  • Hematocrit (if low, mother will receive iron supplementation)
  • Glucose loading test (GLT) - screens for gestational diabetes; if > 140 mg/dL, a glucose tolerance test (GTT) is administered; a fasting glucose > 105 mg/dL suggests gestational diabetes.
Most doctors do a sugar load in a drink form of 50 grams of glucose in cola, lime or orange and draw blood an hour later (plus or minus 5 minutes) ; the standard modified criteria have been lowered to 135 since the late 1980s

Complications

Fetal assessments

Ultrasound is routinely used for dating the gestational age of a pregnancy from the size of the fetus, the most accurate dating being in first trimester before the growth of the fetus has been significantly influenced by other factors. Ultrasound is also used for detecting congenital anomalies (or other fetal anomalies) and determining the biophysical profiles (BPP), which are generally easier to detect in the second trimester when the fetal structures are larger and more developed. Specialised ultrasound equipment can also evaluate the blood flow velocity in the umbilical cord, looking to detect a decrease/absence/reversal or diastolic blood flow in the umbilical artery.

Other tools used for assessment include:

Childbirth

Induction

Induction is a method of artificially or prematurely stimulating labour in a woman. Reasons to induce can include pre-eclampsia, the birth mass, diabetes, and other various general medical conditions, such as renal disease. Induction may occur any time after 34 weeks of gestation if the risk to the fetus or mother is greater than the risk of delivering a premature fetus regardless of lung maturity. If a woman does not eventually labour by 41–42 weeks, induction may be performed, as the placenta may become unstable after this date.

Induction may be achieved via several methods:

Labor

During labor itself, the obstetrician/doctor/intern/medical student under supervision may be called on to do a number of tasks. These tasks can include:
  • Monitor the progress of labor, by reviewing the nursing chart, performing vaginal examination, and assessing the trace produced by a fetal monitoring device (the cardiotocograph)
  • Accelerate the progress of labor by infusion of the hormone oxytocin
  • Provide pain relief, either by nitrous oxide, opiates, or by epidural anesthesia done by anaesthestists, an anesthesiologist, or a nurse anesthetist.
  • Surgically assisting labor, by forceps or the Ventouse (a suction cap applied to the fetus' head)
  • Caesarean section, if there is an associated risk with vaginal delivery, as such fetal or maternal compromise supported by evidence and literature. Caesarean section can either be elective, that is, arranged before labor, or decided during labor as an alternative to hours of waiting. True "emergency" Cesarean sections include abruptio placenta, and are more common in multigravid patients, or patients attempting a Vaginal Birth After Caeserean section (VBAC).


Emergencies in obstetrics

The main emergencies include:

  • Ectopic pregnancy is when an embryo implants in the Fallopian tube or (rarely) on the ovary or inside the peritoneal cavity. This may cause massive internal bleeding.
  • Pre-eclampsia is a disease which is defined by a combination of signs and symptoms that are related to maternal hypertension. The cause is unknown, and markers are being sought to predict its development from the earlist stages of pregnancy. Some unknown factors cause vascular damage in the endothelium, causing hypertension. If severe, it progresses to eclampsia, where a convulsions occur, which can be fatal. Preeclamptic patients with the HELLP syndrome show liver failure and Disseminated intravascular coagulation (DIC).
  • Placental abruption where the patient can bleed to death if not managed appropriately.
  • Fetal distress where the fetus is getting compromised in the uterine environment.
  • Shoulder dystocia where one of the fetus' shoulders becomes stuck during vaginal birth, especially in macrosomic babies of diabetic mothers.
  • Uterine rupture can occur during obstructed labor and endangered fetal and maternal life.
  • Prolapsed cord refers to the prolapse of the fetal cord during labor with the risk of fetal suffocation.
  • Obstetrical hemorrhage may be due to a number of factors such as placenta previa, uterine rupture of tears, uterine atony, retained placenta or placental fragments, or bleeding disorders.
  • Puerperal sepsis is a progressed infection of the uterus during or after labor.


Imaging, monitoring and care

In present society, medical science has developed a number of procedures to monitor pregnancy.

Antenatal record

On the first visit to her obstetrician or midwife, the pregnant woman is asked to carry out the antenatal record, which constitutes a medical history and physical examination. On subsequent visits, the gestational age (GA) is rechecked with each visit.

Symphysis-fundal height (SFH; in cm) should equal gestational age after 20 weeks of gestation, and the fetal growth should be plotted on a curve during the antenatal visits. The fetus is palpated by the midwife or obstetrician using Leopold maneuver to determine the position of the baby. Blood pressure should also be monitored, and may be up to 140/90 in normal pregnancies. High blood pressure indicates hypertension and possibly pre-eclampsia, if severe swelling (edema) and spilled protein in the urine are also present.

Fetal screening is also used to help assess the viability of the fetus, as well as congenital problems. Genetic counseling is often offered for families who may be at an increased risk to have a child with a genetic condition.Amniocentesis at around the 20th week is sometimes done for women 35 or older to check for Down's Syndrome and other chromosome abnormalities in the fetus.

Even earlier than amniocentesis is performed, the mother may undergo the triple test, nuchal screening, nasal bone, alpha-fetoprotein screening and Chorionic villus sampling, also to check for disorders such as Down Syndrome. Amniocentesis is a prenatal genetic screening of the fetus, which involves inserting a needle through the mother's abdominal wall and uterine wall, to extract fetal DNA from the amniotic fluid. There is a risk of miscarriage and fetal injury with amniocentesis because it involves penetrating the uterus with the baby still in utero.

Imaging



Imaging is another important way to monitor a pregnancy. The mother and fetus are also usually imaged in the first trimester of pregnancy. This is done to predict problems with the mother; confirm that a pregnancy is present inside the uterus; estimate the gestational age; determine the number of fetuses and placentae; evaluate for an ectopic pregnancy and first trimester bleeding; and assess for early signs of anomalies.

X-rays and computerized tomography (CT) are not used, especially in the first trimester, due to the ionizing radiation, which has teratogenic effects on the fetus. Instead, ultrasound is the imaging method of choice in the first trimester and throughout the pregnancy, because it emits no radiation, is portable, and allows for realtime imaging.

Ultrasound imaging may be done at any time throughout the pregnancy, but usually happens at the 12th week (dating scan) and the 20th week (detailed scan).

A normal gestation would reveal a gestational sac, yolk sac, and fetal pole. The gestational age can be assessed by evaluating the mean gestational sac diameter (MGD) before week 6, and the crown-rump length after week 6. Multiple gestation is evaluated by the number of placentae and amniotic sacs present.

Salary

The salary of an obstetrician varies from country to country:

Country Annual salary (US$)
United Kingdommarker 187,771
United Arab Emiratesmarker 231,809
United Statesmarker 236,411


See also



References

Further reading



External links




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