obstetrics - Antenatal care, Signs, Maternal physiology, Prenatal care, Complications, Induction, Labour, Emergencies in obstetrics

The medical and surgical care of pregnancy and childbirth. It involves the prenatal care and assessment of the woman's ability to undergo labour, the assessment of the size and health of the fetus in the womb, the detection of diseases related to pregnancy (eg eclampsia), the diagnosis of the position of the fetus in the uterus, and the conduct of the delivery via the vagina. In special circumstances, delivery may need to be assisted by the use of obstetrical forceps to ease the passage of the head through the pelvic outlet, by vacuum extraction, or by caesarian section. Also important are the control of pain, the use of drugs to influence uterine contraction, and the diagnosis and treatment of complications during pregnancy and in the following period.

Obstetrics (from the Latin obstare, "to stand by") is the surgical specialty dealing with the care of a woman and her offspring during pregnancy, childbirth and the puerperium (the period shortly after birth).

Antenatal care

In obstetric practice, the obstetrician will see a pregnant woman on a regular basis to check the progress of her pregnancy.

The main rationale for these visits is surveillance for diseases of pregnancy which are detectable.

Signs

Trimesters

First trimester: elevated β-hCG (human chorionic gonadotrophin)of up to 100,000 mIU/mL by 10 weeks GA can cause morning sickness, fatigue, mood swings and food cravings.

Second trimester: The abdomen shows an obvious swelling arising from the pelvis, starting the "obvious phase" of pregnancy.

Overall

Bluish discoloration of vagina and cervix (Chadwick's sign) Softening and cyanosis of cervix after 4 weeks (Goodell's sign) Softening of uterus after 6 weeks (Ladin's sign) Breast swelling and tenderness Linea nigra from umbilicus to pubis Telangiectasias Palmar erythema Amenorrhea Nausea and vomiting Breast pain Fetal movement Sciatica (Pain caused by compression of the sciatic nerve)

Maternal physiology

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.

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. Diastolic blood pressure consequently decreases between 12-26 weeks, and increases again to prepregnancy levels by 36 weeks.

Hematology

The plasma volume increases by 50% and the red blood cell volume increases only by 20-30%. Decrease in platelet concentration to a minimal normal values of 100-150 mil/mL The pregnant woman also becomes hypercoagulable due to increased liver production of coagulation factors, mainly fibrinogen and factor VIII.

Metabolism

During pregnancy, both protein metabolism and carbohydrate metabolism are affected.

Nutrition

Increased caloric requirement by 300 kcal/day Gain of 20 to 30 lb (10 to 15 kg) Increased protein requirement to 70 or 75 g/day Increased folate requirement from 0.4 to 0.8 mg/day (important in preventing neural tube defects)

All patients are advised to take prenatal vitamins to compensate for the increased nutritional requirements.

Gastrointestinal

nausea and vomiting ("morning sickness") due to elevated B-hCG, which should resolve by 14 to 16 weeks prolonged gastric empty time decreased gastroesophageal sphincter tone, which can lead to acid reflux decreased colonic motility, which leads to increased water absorption and constipation

Renal

Increase in kidney and ureter size Increased glomerular filtration rate (GFR) by 50%, which subsides around 20 weeks postpartum Decreased BUN (blood urea nitrogen) and creatinine, and glucosuria (due to saturated tubular reabsorption) Persistent glucosuria can suggest gestational diabetes Increased renin-angiotensin system, causing increased aldosterone levels Plasma sodium does not change because this is offset by the increase in GFR

Pulmonary

Increased tidal volume (30-40%) Decreased total lung capacity (TLC) by 5% due to elevation of diaphragm from uteral compression Decreased expiratory reserve volume 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.

Endocrine

Increased estrogen, which is mainly produced in the placenta Fetal well being is associated with maternal estrogen levels Causes an increase in thyroxine-binding globulin (TBG) Increased human chorionic gonadotropin (β-hCG), which is produced by the placenta. Increased prolactin Increased alkaline phosphatase

Musculoskeleton and dermatology

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)

Others

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

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

complete blood count (CBC) blood type (blood transfusion may be needed in an emergency) general antibody screen (indirect Coombs test) for HDN Rh D negative antenatal patients should receive RhoGam at 28 weeks to prevent Rh disease. Rapid plasma reagent (RPR) which screens for syphilis Rubella antibody screen Hepatitis B surface antigen Gonorrhea and Chlamydia culture PPD for tuberculosis Pap smear Urinalysis and culture HIV screen Group B Streptococcus screen -- will receive IV penicillin if positive (if mother is allergic, alternate therapies include IV clindamycin or IV vancomycin)

Second trimester

MSAFP/triple screen (maternal serum alpha-fetoprotein) - elevation correlated with neural tube defects and decrease correlated with Down's syndrome ultrasound amniocentesis in older patients

Third trimester

hematocrit (if low, mother will receive iron supplementation) glucose loading test (GLT) - screens for gestational diabetes;

Complications

See Complications of Pregnancy

Fetal assessments

Common ultrasound is used for many functions: Dating the gestational age of a pregnancy, most accurate in first trimester Detecting fetal anomalies in the second trimester biophysical profiles (BPP) Blood flow velocity in umbilical cord -- decrease/absence/reversal or diastolic blood flow in the umbilical artery is worrisome. Nonstress test (NST) for fetal heart rate Oxytocin challenge test

Induction

An obstetrician may recommend a woman have her labour induced if it is felt that continuation would be more dangerous to her, the fetus, or both. Reasons to induce include:

pre-eclampsia IUGR diabetes other general medical condition, such as renal disease

Induction may occur any time after 24 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:

pessary of Prostin cream, prostaglandin E2 vaginal or oral administration of misoprostol cervical insertion of a 30-mL Foley catheter surgical induction, by piercing the amnion infusion of oxytocin

Labour

During labour itself, the obstetrician may be called on to do a number of things:

monitor the progress of labour, by reviewing the nursing chart, performing vaginal examination, and assessing the trace produced by a foetal monitoring device (the cardiotocograph) accelerate the progress of labour by infusion of the hormone oxytocin provide pain relief, either by nitrous oxide (nowadays uncommon, at least in the U.S.), opiates, or by epidural anesthesia done by anaethestists or an anesthesiologist surgically assisting labour, by forceps or the Ventouse (a suction cap applied to the fetus' head) Caesarean section, if vaginal delivery is decided against or appears too difficult.

Emergencies in obstetrics

Two main emergencies are ectopic pregnancy and (pre)eclampsia.

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.

Imaging

Imaging is another important way to monitor a pregnancy. 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). The gestational age can be assessed by evaluating the mean gestation sac diameter (MGD) before week 6, and the crown-rump length after week 6.

Pregnancy has different cultural aspects related to the perception of the body, the relationship with partner and to the meaning of the event.

Terms and definitions

embryo - conceptus between time of fertilization to 10 weeks of gestation fetus - from 10 weeks of gestation to time of birth infant - time of birth to 1 year of age gestational age - time from last menstrual period (LMP) up to present first trimester - up to 14 weeks of gestation second trimester - 14 to 28 weeks of gestation third trimester - 28 weeks to delivery viability - minimum age for fetus survival, ca. third trimester previable infant - delivered prior to 24 weeks preterm infant - delivered between 24-37 weeks term infant - delivered between 37-42 weeks gravidity (G) - number of times a woman has been pregnant parity (P) - number of pregnancies with a birth beyond 20 weeks GA or an infant weighing more than 500 g Ga Pw-x-y-z - a = number of pregnancies, w = number of term births, x = number of preterm births, y = number of miscarriages, z = number of living children;