Comprehensive Notes on Pregnancy and Fetal Development

Gravida and Para

• Gravida: Total number of pregnancies a person has had.
• Para: Number of pregnancies that have made it past 20 weeks.
• The 20-week mark is significant because the risk of complications decreases considerably after this stage.
• Example Scenarios:
  • Gravida 0, Para 0: First pregnancy.
  • Gravida 5, Para 4: Fifth pregnancy, with four previous pregnancies going well. Indicates patient may be healthy and not anticipating complications.
  • Gravida 7, Para 0: Potential complications may arise.
• These numbers are essential for tracking and understanding a patient's obstetric history and potential risks.

Menstrual Cycle

• Normal cycle length is approximately 28 days.
• The patient has regular cycles but they are longer, consistently 34 days.

Hormones and Follicle Development

• GnRH (Gonadotropin-Releasing Hormone) helps release FSH (Follicle-Stimulating Hormone).
• FSH helps the follicle start developing.
• LH (Luteinizing Hormone) helps the follicle ovulate; its release is triggered by positive feedback from estrogen.

Fertilization and Implantation

• Fertilization happens in the fallopian tube.
• After ovulation on day 14, the fertilized egg needs to implant in the uterus.
• Intercourse three days before ovulation and up to the day after provides the highest chance of pregnancy.
• Peak time for fertilization is about 2-3 days before ovulation.
• In a 34-day cycle, day 11 might be the peak time for fertilization.

Early Cell Division

• After fertilization, the cell undergoes multiple divisions, forming structures like morula, blastocyst, and gastrula.
• Implantation occurs between 6 to 12 days after ovulation.
• Implantation involves the fertilized egg attaching to the endometrium (specifically the stratum functionalis layer) of the uterus.

Hormonal Communication

• If implantation occurs late (e.g., 12 days after ovulation), there's a short window to signal the body to prevent menstruation.
• The implanted embryo communicates its presence through hormones, primarily to sustain progesterone levels.
• Progesterone helps maintain the endometrial layer.

Role of HCG

• The implanted embryo produces human chorionic gonadotropin (hCG) to sustain progesterone production.
• hCG takes over from GnRH in sustaining progesterone levels.
• Progesterone, typically regulated by GnRH, is sustained by hCG produced by the placenta.
• High progesterone levels during pregnancy inhibit GnRH production through negative feedback.

Timing of HCG Production

• hCG starts being produced in small amounts right after implantation.
• A significant spike in hCG occurs around the time when menstruation would normally happen.
• This spike signals to the body not to menstruate.

Mifepristone

• Mifepristone is a drug that blocks progesterone receptors, effectively signaling the body to start a menstrual period.
• This drug is used to terminate early pregnancies.

Infertility

• Infertility can stem from issues such as failure to develop an egg, failure to ovulate, or difficulty with implantation.
• Conditions like endometriosis can hinder implantation.

Spontaneous Abortion/Miscarriage

• The body may spontaneously abort a pregnancy if certain developmental milestones aren't met.

Morning After Pill

• The morning-after pill is taken within 24 hours of intercourse to prevent pregnancy.
• It works by blocking the spike in luteinizing hormone (LH), thus preventing ovulation.

Surgical Abortion

• Surgical abortions involve physically removing the embryo and are typically less comfortable.

Fertilization and Implantation

• Fertilization should occur in the fallopian tube.
• The fertilized egg takes about a week to move out of the fallopian tube and attach to the uterus.
• If the egg is not fertilized within 24 hours of ovulation, it dies before reaching the uterus.

Pregnancy Detection

• Pregnancy tests detect hCG levels in the blood, typically through urine samples.
• Renal filtrate is similar to blood plasma, so hormones in the blood are also present in the urine.
• Store tests typically detect pregnancy about two days before the missed period.

Sustaining Pregnancy

• hCG’s primary job is to maintain progesterone production, preventing the loss of the endometrium.
• hCG also stimulates estrogen production.
• High estrogen levels can cause various physical changes during pregnancy, such as hair loss, gum issues, calcium imbalances, varicose veins, swelling, and hemorrhoids.

Scurvy

• Scurvy is a disease caused by vitamin C deficiency, although patients may not crave fruit.

Ovarian-Placental Shift

• Around week 8, a shift occurs where the placenta takes over progesterone production from the corpus luteum.
• The corpus luteum is initially responsible for progesterone production but is not sustainable for the entire pregnancy.
• The placenta becomes the primary endocrine organ, sustaining the pregnancy.

Gestational Diabetes

• Gestational diabetes can occur due to hormone imbalances from the placenta.
• The placenta can cause insulin resistance, leading to high blood sugar levels to support the baby's growth.

Delivery

• Delivery typically occurs around the 38th week of pregnancy.
• Conceptional age is counted from fertilization (38 weeks), while gestational age is counted from the beginning of the last menstrual period (40 weeks, adding an extra two weeks for follicle development).

Breast Milk Production

• Prolactin levels increase to prepare for breast milk production.
• The placenta produces hCG, which acts like GnRH to make estrogen and progesterone.
• Oxytocin helps with breast milk release and uterine contractions during delivery.

Ages

• Conceptional age: 38 weeks from fertilization to delivery.
• Gestational age: 40 weeks counted from the beginning of the last menstrual period.

Pregnancy Test Mechanism

• Pregnancy tests detect hCG in urine.
• Antibodies shaped like "Y" bind to hCG.
• A chemical is added to the antibody to make it visible.
• First-morning urine is recommended to avoid dilution and ensure accurate results.

Test Procedure

1. Urine is applied to the sample area.
2. If hCG is present, it encounters and binds to antibodies in the test.
3. The urine wicks downstream, carrying antibodies with it.
4. The test strip features two lines: a test line and a control line.

Line functions on the test:

• The first antibody (anti-hCG) is stuck to the test line and binds to hCG.
• The second antibody sticks to all antibodies, ensuring the test works correctly.

Test Results:

• No bands: The test did not work and needs to be repeated.
• One line (control line): The test worked, but the result is negative (not pregnant).
• Two lines (test and control lines): The test worked, and the result is positive (pregnant).

False positives are rare.

Hospital Procedures

• Hospitals perform pregnancy tests (urine) on all biological females of childbearing age before any treatment.
• Blood tests are quantitative, providing numerical hCG levels in milli international units per milliliter (mIU/mL).

Blood test values:

• Less than 5 mIU/mL: Not pregnant.
• Over 25 mIU/mL: Definitely pregnant.
• Between 5 and 25 mIU/mL: Inconclusive and needs to be repeated.

Timeline

• Implantation: 6-12 days after ovulation is required before hCG is made.
• Tests: Pregnancy tests can be presumptive or definitive, with definitive tests conducted in certified medical labs.

Landmarks in Fetal Development

• After the embryo implants, the nervous system and heart are the first to develop.
• Solid line: Major developmental milestones and devastating results in case of issues during these stages.
• Dashed line: Still some development happening, but not as critical and not as devastating results. It means less likely to be fatal.
• The ears are fully developed by week 38.
• The period where a person is least likely to know they are pregnant is also when the most critical developmental milestones are occurring.
• Remember the order of fetal development

Sexual Differentiation

• External genitalia development begins around week 7.
• Up to this point, the genitalia are neutral with elements of both male and female structures.
• Testosterone determines the development path.
• Wolffian ducts develop into male structures when testosterone is present.
• Mullerian ducts develop into female structures when testosterone is absent.
• Without testosterone, the system defaults to female development.