Obstetrics is the health profession or medical specialty that deals with pregnancy, childbirth, and postpartum period.

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
First trimester screening varies by country. Women will typically be offered: Complete Blood Count (CBC), Blood Group and Antibody screening (Group and Save), Syphilis, Hepatitis B, HIV, Rubella immunity and urine microbiology and sensitivity to test for bacteria in the urine without symptoms. Additionally, women under 25 years of age will be offered chlamydia testing via a urine sample, and women considered high risk will be screened for Sickle Cell disease and Thalassemia. Women must consent to all tests before they are carried out. The woman's blood pressure, height and weight will also be measured, and her Body Mass Index (BMI) will be calculated. This is the only time her weight will be recorded routinely. Her family history, obstetric history, medical history and social history will also be discussed.
Women usually have their first ultrasound scan at around twelve weeks. This is a trans-abdominal ultrasound. This is the scan from which the pregnancy is dated and the woman's estimated due date (or EDD) is worked out. At this scan, some NHS Trusts offer women the opportunity to have screening for Down's Syndrome. If it is done at this point, both the nuchal fold is measured and a blood test taken from the mother. The result comes back as an odd's risk for the fetus having Down's Syndrome. This will be specified as somewhere between 1:2 (high risk) to 1:100,000 (low risk). High risk women (who have a risk of greater than about 1:150) will be offered further tests, which are diagnostic. These tests are invasive and carry a risk of miscarriage.
Genetic screening for downs syndrome (trisomy 21) and trisomy 18 the 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 βHCG (pregnancy hormone level itself). It gives an accurate risk profile very early. There is a second blood screen at 15 to 20 weeks which refines the risk more accurately. The cost is higher than an "AFP-quad" screen due to the ultrasound and second blood test but it is quoted to have a 93% pick up rate as opposed to 88% for the standard AFP/QS. This is an evolving standard of care in the United States.

Second trimester
The second trimester is when women start to see their midwife. Other than the booking appointment at around ten weeks and her ultrasound scan at around twelve weeks, she will not have had much contact with health care professionals regarding her pregnancy. The actual schedule of appointments varies by NHS Trust, but the woman can expect to see her midwife around sixteen weeks. At this appointment, the results of the screening and tests carried out at her booking appointment will be discussed. The woman's blood pressure will be measured and a urinalysis carried out. The woman will be given the opportunity to ask any questions she may have. Some women may choose to ask to listen to the fetal heart at this appointment. This should not be routinely offered by the midwife as at 16 weeks gestation, the heartbeat can be difficult to detect and some NHS Trusts will not scan at this point if the midwife is unable to hear the fetal heart.
At around twenty weeks, the woman will have an anomaly scan. This trans-abdominal ultrasound scan checks on the anatomical development of the fetus. It is a detailed scan and checks all the major organs. As a consequence, if the fetus is not in a good position for the scan to be preformed, the woman may be sent off for a walk and then asked to return. At this scan, the position of the placenta is noted, to ensure it is not low. Cervical assessment is not routinely carried out.

Third trimester
During the third trimester, women will have further blood tests taken. Blood will be taken for Full Blood Count (FBC) and a Group and Save will be taken to confirm her blood group and as a further check for any antibodies. This may routinely be done twice in the third trimester. A Glucose Tolerance Test (GTT) will be done for women with risk factors for Gestational Diabetes. This includes women with a raised BMI, women of certain ethnic origins and women who have a first degree relative with diabetes. A vaginal swab for Group B Streptococcus (GBS) will only be taken for women who are known to have had a GBS-affected baby in the past or for women who have had a urine culture positive for GBS during this pregnancy.
 
Women will see this midwife more frequently as they progress through pregnancy. First time mums, or mums on the high risk care pathway, may see the midwife at around twenty four weeks, when the midwife will offer to listen to the fetal heart. From twenty eight weeks, the midwife will measure the symphysis fundal height (or SFH) to measure the growth of the abdomen. This is currently the best method available to easily check the fetal growth, but it is not perfect. At appointments, the midwife will check the woman's blood pressure and do a urinalysis. The midwife will palpate the woman's abdomen to establish the lie, presentation and position of the fetus, and later, the engagement. The midwife will offer to listen to the fetal heart.
 
From the woman's due date, the midwife may offer to do a stretch and sweep. This involves a vaginal examination, where the midwife will assess the cervix and attempt to sweep the membranes. This releases a hormone called prostaglandin, which is believed to help the cervix prepare for labour.
 
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.
 
The woman is given her notes at her booking appointment with the midwife. Following an assessment by the midwife, the woman's notes are put together and the woman is responsible for these notes. They are called her hand held records. The woman is advised to carry these with her at all times and to take them with her when she sees any healthcare professional. Following the anomaly scan, some NHS Trusts will print out a customized growth chart. This takes in to account the woman's size and the size of any previous babies when decided what her 'normal range' is for SFH growth.
 
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 the 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. However, a significant rise in blood pressure, even below the 140/90 threshold, may be a cause for concern High blood pressure indicates hypertension and possibly pre-eclampsia if other symptoms are present. These may include swelling (edema), headaches, visual disturbances, epigastric pain and proteinurea.
 
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, which is usually performed between 15 and 20 weeks, to check for Down syndrome, other chromosome abnormalities or other conditions in the fetus, is sometimes offered to women who are at increased risk due to factors such as older age, previous affected pregnancies or family history. Amniocentesis, and other invasive investigations such as chorionic villus sampling, is not preformed in the UK as frequently as it is in other countries, and in the UK, advanced maternal age alone is not an indication for such an invasive procedure
 
Even earlier than amniocentesis is performed, the mother may undergo the triple test, nuchal screening, nasal bone, alpha-fetoprotein screening, Chorionic villus sampling, and 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 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. No effects of magnetic resonance imaging (MRI) on the fetus have been demonstrated, but this technique is too expensive for routine observation. Instead, obstetric ultrasonography 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).
 
The safety of frequent ultrasound scanning has not be confirmed. Despite this, increasing numbers of women are choosing to have additional scans for no medical purpose, such as gender scans, 3D and 4D scans.
 
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.
   Obstetric ultrasonography is the application of medical ultrasonography to obstetrics, in which sonography is used to visualize the embryo or fetus in its mother's uterus (womb). The procedure is a standard part of prenatal care, as it yields a variety of information regarding the health of the mother and of the fetus, the progress of the pregnancy, and further information on the baby.
In those who are at low risk it is unclear if obstetric ultrasound before 24 weeks makes a significant difference in outcomes.
 
Types
Traditional obstetric sonograms are done by placing a transducer on the abdomen of the pregnant woman. One variant, a transvaginal sonography, is done with a probe placed in the woman's vagina. Transvaginal scans usually provide clearer pictures during early pregnancy and in obese women. Also used is Doppler sonography which detects the heartbeat of the fetus. Doppler sonography can be used to evaluate the pulsations in the fetal heart and bloods vessels for signs of abnormalities.
 
Early pregnancy
The gestational sac can sometimes be visualized as early as four and a half weeks of gestational age (approximately two and a half weeks after ovulation) and the yolk sac at about five weeks gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as 5 weeks of gestational age. It is usually visible by 7 weeks. Coincidentally, most miscarriages also happen by 7 weeks gestation. The rate of miscarriage, especially threatened miscarriage, drops significantly if normal heartbeat is detected.
 
Dating and growth monitoring
Gestational age is usually determined by the date of the woman's last menstrual period, and assuming ovulation occurred on day fourteen of the menstrual cycle. Sometimes a woman may be uncertain of the date of her last menstrual period, or there may be reason to suspect ovulation occurred significantly earlier or later than the fourteenth day of her cycle. Ultrasound scans offer an alternative method of estimating gestational age. The most accurate measurement for dating is the crown-rump length of the fetus, which can be done between 7 and 13 weeks of gestation. After 13 weeks of gestation, the fetal age may be estimated using the biparietal diameter (the transverse diameter of the head), the head circumference, the length of the femur, the crown-heel length (head to heel), and other fetal parameters. Dating is more accurate when done earlier in the pregnancy; if a later scan gives a different estimate of gestational age, the estimated age is not normally changed but rather it is assumed the fetus is not growing at the expected rate.
 
Not useful for dating, the abdominal circumference of the fetus may also be measured. This gives an estimate of the weight and size of the fetus and is important when doing serial ultrasounds to monitor fetal growth.
 
Ultrasonography of the cervix
Obstetric sonography has become useful in the assessment of the cervix in women at risk for premature birth. A short cervix preterm is undesirable: At 24 weeks gestation a cervix length of less than 25 mm defines a risk group for preterm birth, further, the shorter the cervix the greater the risk. It also has been helpful to use ultrasonography in women with preterm contractions, as those whose cervix length exceed 30 mm are unlikely to deliver within the next week.
 
Abnormality screening
In some countries, routine pregnancy sonographic scans are performed to detect developmental defects before birth. This includes checking the status of the limbs and vital organs, as well as (sometimes) specific tests for abnormalities. Some abnormalities detected by ultrasound can be addressed by medical treatment in utero or by perinatal care, though indications of other abnormalities can lead to a decision regarding abortion.
 
Perhaps the most common such test uses a measurement of the nuchal translucency thickness ("NT-test", or "Nuchal Scan"). Although 91% of fetuses affected by Down syndrome exhibit this defect, 5% of fetuses flagged by the test do not have Down syndrome.
 
Ultrasound may also detect fetal organ anomaly. Usually scans for this type of detection are done around 18 to 23 weeks of gestational age. Some resources indicate that there are clear reasons for this and that such scans are also clearly beneficial because ultrasound enables clear clinical advantages for assessing the developing fetus in terms of morphology, bone shape, skeletal features, fetal heart function, volume evaluation, and general fetus well being.
 
3D ultrasound
Modern 3D ultrasound images provide greater detail for prenatal diagnosis than the older 2D ultrasound technology. While 3D is popular with parents desiring a prenatal photograph as a keepsake, both 2D and 3D are discouraged by the FDA for non-medical use, but there are no definitive studies linking ultrasound to any adverse medical effects.
  Obstetric ultrasonography 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:

• Fetal karyotype can be used for the screening of genetic diseases. This can be obtained via amniocentesis or chorionic villus sampling (CVS)
• Fetal hematocrit for the assessment of fetal anemia, Rh isoimmunization, or hydrops can be determined by percutaneous umbilical blood sampling (PUBS) which is done by placing a needle through the abdomen into the uterus and taking a portion of the umbilical cord.
• Fetal lung maturity is associated with how much surfactant the fetus is producing. Reduced production of surfactant indicates decreased lung maturity and is a high risk factor for infant respiratory distress syndrome. Typically a lecithin:sphingomyelin ratio greater than 1.5 is associated with increased lung maturity.
• Nonstress test (NST) for fetal heart rate
• Oxytocin challenge test

  The main emergencies include:

• Ectopic pregnancy is when an embryo implants in the uterine (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 earliest stages of pregnancy. Some unknown factors cause vascular damage in the endothelium, causing hypertension. If severe, it progresses to eclampsia, where seizuresoccur, which can be fatal. Preeclamptic patients with the HELLP syndrome show liver failure and Disseminated intravascular coagulation (DIC). The only treatment is to deliver the fetus. Women may still develop pre-eclampsia following delivery.
• Placental abruption is where the placenta detaches from the uterus and the woman and fetus 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. There are many risk factors, including macrosmic (large) fetus, but many are also unexplained.
• Uterine rupture can occur during obstructed labor and endanger fetal and maternal life.
• Prolapsed cord can only happen after the membranes have ruptured. The umbilical cord delivers before the presenting part of the fetus. If the fetus is not delivered within minutes, or the pressure taken off the cord, the fetus will die.
• Obstetrical hemorrhage may be due to a number of factors such as placenta previa, uterine rupture or tears, uterine atony, retained placenta or placental fragments, or bleeding disorders.
• Puerperal sepsis is an ascending infection of the genital tract. It may happen during or after labour. Signs to look out for include signs of infection (pyrexia or hypothermia, raised heart rate and respiratory rate, reduced blood pressure), and abdominal pain, offensive lochia (blood loss) increased lochia, clots, diarrhea and vomiting.

In addition to complications of pregnancy that can arise, a pregnant woman may have intercurrent diseases, that is, other diseases or conditions (not directly caused by the pregnancy) that may become worse or be a potential risk to the pregnancy.

• Diabetes mellitus and pregnancy deals with the interactions of diabetes mellitus (not restricted to gestational diabetes) and pregnancy. Risks for the child include miscarriage, growth restriction, growth acceleration, fetal obesity (macrosomia), polyhydramnios and birth defects.
• Systemic lupus erythematosus and pregnancy confers an increased rate of fetal death in utero and spontaneous abortion (miscarriage), as well as of neonatal lupus.
• Thyroid disease in pregnancy can, if uncorrected, cause adverse effects on fetal and maternal well-being. The deleterious effects of thyroid dysfunction can also extend beyond pregnancy and delivery to affect neurointellectual development in the early life of the child. Demand for thyroid hormones is increased during pregnancy which may cause a previously unnoticed thyroid disorder to worsen.
• Hypercoagulability in pregnancy is the propensity of pregnant women to develop thrombosis (blood clots). Pregnancy itself is a factor of hypercoagulability (pregnancy-induced hypercoagulability), as a physiologically adaptive mechanism to prevent post partum bleeding. However, when combined with an additional underlying hypercoagulable states, the risk of thrombosis or embolism may become substantial.