- Clinical science
Pregnancy begins with the fertilization of the ovum and subsequent implantation into the uterine wall. The duration of pregnancy is counted in weeks of gestation from the first day of the last menstrual period and on average lasts 40 weeks. Presumptive signs of pregnancy include amenorrhea, nausea and vomiting, and breast enlargement and tenderness. Pregnancy can be confirmed definitively via positive serum or urine hCG tests and detection of the embryo on ultrasound. Ultrasound is also used to determine the gestational age and date of delivery. Women experience several benign, physiological changes during pregnancy (e.g., peripheral edema, dyspnea, increased urinary frequency). Regular check-ups should be performed to detect possible high-risk pregnancies as well as fetal and maternal complications.
- The duration of pregnancy is counted in weeks of gestation from the first day of the last menstrual period
- Completed weeks of gestation + completed days (0–6) of the current week of pregnancy
- Normal duration of pregnancy: 40 weeks (280 days)
- : live birth before the completion of 37 weeks (< 37 0/7) of pregnancy
- Post-term birth: live birth after 42 weeks (> 42 0/7) of pregnancy
Pregnancy is divided into trimesters:
- First trimester (week 1–13): highest risk of miscarriage
- Second trimester (week 14–26)
- Third trimester (week 27–40)
|Day 0|| |
|Days 6–12|| |
|Week 3|| |
|From week 9|| |
The earlier disruptions take place during fetal development, the more complicated the resulting congenital anomalies!
Confirmation of pregnancy
Pregnancy test: measurement of human chorionic gonadotropin (beta-hCG)
- Urine beta-hCG test (e.g., home pregnancy test)
Serum beta-hCG test (quantitative, high sensitivity)
- Detectable 6–9 days (on average) after fertilization
- Normal pregnancy: beta-hCG concentration doubles every 2.5 days in early pregnancy
- Peaks at 10 weeks of gestation (peak value: ∼100,000 mlU/mL) and then declines
- Beta-hCG level of 1,500–2,000 mlU/mL → pregnancy visible with transvaginal ultrasound (if beta-hCG < 1000 mlU/mL, repeat beta-hCG and transvaginal ultrasound in 2–3 days)
- Low values or slow rise in the value: may indicate ,
- High values or fast rise in the value: may indicate beta-hCG secreting tumors ( , ),
- False-positive test results:
- Normal pregnancy: beta-hCG concentration doubles every 2.5 days in early pregnancy
Ultrasound findings in normal pregnancy (abdominal or transvaginal)
- At 5–6 weeks of pregnancy: detection of the embryo
- At 10–12 weeks of pregnancy: detection of fetal heartbeat with Doppler ultrasound
- At 18–20 weeks of pregnancy: fetal movements
Transvaginal ultrasound findings
|Weeks after last menstruation||β-hCG mlU/mL|
|Fetal heartbeat||8||17000Determining the gestational age and date of delivery|
- Gestational age: the age (in weeks and days) of the fetus calculated from the first day of the last menstrual period
- Embryonic age: the age (in weeks and days) of the fetus calculated from the day of conception (fertilization)
Naegele's rule: used to calculate the date of delivery (due date)
- First day of the last menstrual period + 7 days + 1 year - 3 months
- Inaccurate if:
- The date of the last menstrual period is uncertain or unknown.
- The patient has irregular menstruation cycles.
- The patient conceived while taking contraceptive pills.
Ultrasound: more accurate than Naegele's rule
- Measurement of the crown-rump length (CRL) in the first trimester
- Measurement of biparietal diameter, femur length, and abdominal circumference (starting at 14 weeks)
- gestational age : correlates with the
Numerous physiological changes occur during pregnancy in order to support fetal growth and prepare for delivery.
|Mammary glands|| |
|Vulva and vagina|
- Nutritional intake needs to be adapted to meet both the demands of the mother and the fetus.
- Dietary recommendations:
- Limit caffeine intake: daily recommended dose < 200 mg
- Avoid alcohol and tobacco use throughout pregnancy
- Avoid unwashed or uncooked foods
- Raw fish (contamination with parasites and bacteria) and seafood of unknown origin (methylmercury contamination)
- Raw milk products: high risk of
- Raw meat: high risk of
- Supplementation of vitamins and minerals is recommended.
|Supplementation||Reason for increased demand||Consequences of deficiency|
|Folic acid|| |
|Vitamin B12|| || || |
|Iron|| || |
|Calcium|| || |
|Iodine|| || || |
- The recommendations are determined by the BMI prior to the pregnancy:
- Average recommended daily calorie intake:
- First trimester: 2200 kcal
- Second and third trimester: 2500 kcal
- Regular physical activity is recommended (contact sport should be avoided).
- Regular physical activity (i.e., aerobic and strength-training exercise) is considered beneficial and is recommended before, during, and after pregnancy.
- Careful evaluation of medical and obstetric disorders is necessary before recommending any exercise program.
- Modifying normal exercise routines may be necessary; activities considered unsafe should be avoided.
|Safe and unsafe activities during pregnancy|
|Safe activities*|| |
|Unsafe activities|| |
* In pregnancies without complications as determined by an obstetrician
** Avoid positions associated with ↓ venous return
*** May be considered safe in women who took part in these exercises before the pregnancy and as determined by an obstetrician
Physical activity should be discontinued if the patient presents with any of the following: antepartum or postpartum hemorrhage, uterine contractions, amniotic fluid leakage, chest pain, dyspnea before exertion, dizziness, headaches, calf pain/swelling, and/or muscle weakness with impaired balance!
Early identification of high-risk pregnancies is vital in order to prevent the occurrence of maternal and fetal complications, which are associated with high morbidity and mortality rates. High-risk pregnancies require regular prenatal care to monitor and support the pregnant mother (see ).
Risk factors for a complicated pregnancy
- Family history (medical and obstetric) of complicated pregnancies
- Personal history
- Advanced maternal age (> 35 years)
- First pregnancy
- Multiparity (> 5 births)
- Medical conditions (epilepsy, malignancies) , arterial , ,
- Social and environmental factors (e.g., drug use, stress)
- Pre-existing gynecological conditions: uterine myoma, history of uterine surgery
- Prior complicated pregnancies
- Complications that arise during pregnancy (See “Maternal complications during pregnancy” and “Fetal complications during pregnancy” below.)
Nausea and vomiting of pregnancy
Uncomplicated nausea and vomiting (“morning sickness”)
- Epidemiology: occurs in up to 90% of pregnancies; onset at 5–6 weeks' gestation, peaking at 9 weeks' gestation, usually abating by 16–20 weeks' gestation
- Risk factors
- Nausea and/or vomiting
- Normal vital signs, lab findings, and normal physical examination
- Definition: : severe, persistent nausea and vomiting associated with a > 5% loss of pre-pregnancy weight and ketonuria with no other identifiable cause
- Clinical features: nausea, vomiting, physical signs of dehydration, hypersalivation, orthostatic hypotension, malnourishment
- Definition: painless cervical dilation, in the absence of uterine contractions; and/or labor, in the second trimester of pregnancy
- Etiology: Most cases are idiopathic.
- Risk factors
- Painless cervical dilation with or without prolapsed membranes
- Nonspecific findings
- Pelvic cramps or back ache
- ↑ Volume, changed color (yellow or blood-stained), and/or thinner consistency of vaginal discharge
- Clinical diagnosis typically before 24 weeks' (may be up to 28 weeks') gestation; or
- History of ≥ 2 previous midtrimester pregnancy losses or ≥ 3 preterm births; not explained by any other cause, and a transvaginal ultrasound cervical length < 25 mm before 24 weeks' gestation
- Serial cervical ultrasound monitoring should be commenced in high-risk women (i.e., previous preterm birth) between 16–24 weeks' gestation.
- Definition: placement of a supportive suture in the cervicovaginal junction to prevent early pregnancy loss or preterm birth
- Methods: McDonald cerclage , Shirodkar cerclage
- Current singleton pregnancy, previous preterm birth at < 34 weeks' gestation, and a short cervical length at < 24 weeks' gestation
- Current singleton pregnancy with a clinical diagnosis of cervical insufficiency at < 24 weeks' gestation
- Prior cerclage due to cervical insufficiency at < 24 weeks' gestation
- Vaginal progesterone supplementation: indicated for a short cervical length at < 24 weeks' gestation in the absence of a previous preterm birth
- Strict bed rest is not recommended.
A shortened cervical length alone is not sufficient to diagnose cervical insufficiency.
Supine hypotensive syndrome: compression of the vena cava and pelvic veins by the uterus may occur during the third trimester of pregnancy as a result of the mother lying in a supine position.
- Venous return to the heart is disturbed and the cardiac output per minute decreases → fetal hypoxia → CTG shows ↓ FHR as a prolonged deceleration
- After repositioning the mother in the left lateral position, the FHR recovers.
- In the mother, supine hypotensive syndrome is characterized by tachycardia, dizziness, and nausea, and occasionally causes syncope.
- Peripheral edema
- Musculoskeletal condition
- (most common pregnancy complication)
Cephalopelvic disproportion: the fetal size is disproportionately large for the maternal pelvis
- Can result in a
- Polymorphic eruption of pregnancy
- Maternal conditions during pregnancy (e.g., malignancy, infections, trauma)
- Definition: amount of amniotic fluid < 500 mL in the third trimester
- Intrauterine growth restriction (diminished mobility of the fetus)
- Intrauterine compression and decreased amniotic fluid ingestion → Potter sequence: pulmonary hypoplasia (cause of death due to severe neonatal respiratory insufficiency), craniofacial abnormalities, limb anomalies
- Birth complications (e.g., umbilical cord compression)
- Definition: excessive amniotic fluid volume (> 2000 mL in the third trimester) that results in uterine distention and is associated with an increased risk of fetal complications