OG2.1,OG3.1,OG4.1,OG5.1-2,OG6.1,OG7.1 | Foundations of Reproduction and Pregnancy — Glossary

ACE inhibitors (e.g. lisinopril, enalapril) cause fetal renal tubular dysplasia, oligohydramnios, intrauterine growth restriction, and neonatal renal failure particularly in the second and third trimesters; must be substituted before or at conception.

The exocytosis of the sperm acrosomal cap upon contact with the zona pellucida, releasing hydrolytic enzymes (including acrosin) that digest a pathway through the zona, allowing sperm penetration.

The widest and longest part of the fallopian tube (~5 cm); the normal site of fertilisation and the most common location of tubal ectopic pregnancy.

An autoimmune thrombophilia characterised by antiphospholipid antibodies (anticardiolipin, anti-β2-GPI, lupus anticoagulant) causing recurrent arterial/venous thrombosis and recurrent pregnancy loss; tested in women with ≥2 consecutive miscarriages or early severe pre-eclampsia.

Compression of the inferior vena cava (reducing venous return) and aorta by the gravid uterus in the supine position after 20 weeks; causes supine hypotensive syndrome; prevented by left lateral tilt ≥15°.

The rebound of the fetus when the cervix is tapped upward through the vaginal fornix on bimanual examination, detectable from approximately 16–20 weeks; a probable sign of pregnancy.

The greater vestibular glands, lying at the 4 and 8 o'clock positions posterior to the vaginal orifice; their duct obstruction produces a Bartholin's cyst.

The hollow fluid-filled structure formed from the morula approximately 4–5 days post-fertilisation, consisting of an outer trophoblast layer and inner cell mass; the stage at which implantation occurs.

Painless, irregular, non-progressive uterine contractions detectable from 6 weeks gestation that prepare the myometrium for labour; they do not cause cervical change.

The physiological maturation process that spermatozoa undergo in the female genital tract, enabling them to undergo the acrosome reaction and fertilise an oocyte; involves cholesterol removal from the sperm membrane and hyperactivation of flagellar movement.

The volume of blood pumped by the heart per minute (heart rate × stroke volume); rises 30–50% in pregnancy, peaking at 28–32 weeks.

The Mackenrodt's or transverse cervical ligament — the chief mechanical support of the uterus, running from the lateral cervix and upper vagina to the pelvic side wall; traversed by the ureter.

Bluish-violet discolouration of the vaginal mucosa and cervix due to venous congestion and increased vascularity from rising oestrogen, appearing from approximately 6–8 weeks of pregnancy; a probable sign.

The branching structural unit of the placenta, consisting of a fetal capillary within a stromal core covered by cytotrophoblast and syncytiotrophoblast; the site of fetomaternal exchange.

The temporary endocrine structure formed from the ruptured Graafian follicle after ovulation; secretes progesterone and oestradiol; persists for approximately 14 days unless rescued by hCG from the implanting trophoblast.

The exocytosis of cortical granules from beneath the oocyte plasma membrane immediately after sperm–oocyte fusion; the released enzymes modify and harden the zona pellucida, preventing additional sperm from penetrating (primary block to polyspermy).

One of the 15–30 lobules forming the maternal surface of the placenta, each consisting of a main stem villus and its branches; separated from adjacent cotyledons by decidual septa.

The window of gestation during which a specific organ or structure is most susceptible to teratogen-induced malformation; corresponds to the period of active organogenesis for that structure; varies by organ system (e.g., neural tube: days 22–28 post-fertilisation; heart: weeks 4–7).

The measurement from the crown of the head to the coccygeal end of the fetal spine on ultrasound; the most accurate gestational age dating parameter when measured at 11–13 weeks (approximately 5.5–6 cm at 12 weeks).

The inner mononuclear, mitotically active cellular layer of the chorionic villi (also called Langhans cells); serves as the progenitor pool for the syncytiotrophoblast and gives rise to extravillous trophoblast cells that invade the decidua and spiral arteries.

The transformation of endometrial stromal cells under progesterone into large, glycogen-rich decidual cells, forming the decidua basalis (placental component), capsularis (covers embryo), and parietalis (lines rest of cavity); regulates trophoblast invasion.

The serum β-hCG level (approximately 1,500–2,000 mIU/mL on transvaginal ultrasound) above which a viable intrauterine gestational sac should be visible; an empty uterus above this threshold is highly suspicious for ectopic pregnancy.

The simultaneous Bohr shift in both maternal and fetal haemoglobin at the placenta: fetal CO₂ release into the intervillous space alkalinises the fetal blood (HbF shifts left, increasing O₂ uptake) while acidifying maternal blood (HbA shifts right, increasing O₂ release), collectively maximising O₂ transfer from mother to fetus.

Irreversible pulmonary hypertension resulting from chronic left-to-right cardiac shunting causing vascular remodelling and eventual shunt reversal; pregnancy is associated with >25% maternal mortality and is WHO class IV — advise against pregnancy.

Weeks 1–8 post-fertilisation (weeks 3–10 gestational age); the phase during which all major organ systems are established by differentiation of the three germ layers; the critical window for structural teratogens.

The innermost mucosal layer of the uterus; undergoes cyclical proliferative and secretory changes under oestrogen and progesterone, and is shed at menstruation.

The estimated date of term delivery, calculated as 280 days (40 weeks) from the first day of the last menstrual period (Naegele's rule), or based on crown-rump length from the first-trimester dating scan.

The receptor on the syncytiotrophoblast that mediates selective transfer of maternal IgG across the placenta to the fetus by receptor-mediated endocytosis; explains why IgG (but not IgM) crosses the placenta and provides passive neonatal immunity.

The clinical condition in which a fetus fails to achieve its genetic growth potential, typically defined as an estimated fetal weight below the 10th centile for gestation; most commonly caused by placental insufficiency in early-onset forms.

The predominant haemoglobin in fetal red blood cells, composed of two alpha and two gamma subunits (α₂γ₂); has a higher oxygen affinity than adult HbA because the gamma subunits bind 2,3-DPG less avidly, resulting in a left-shifted oxygen dissociation curve.

Week 9 post-fertilisation to delivery; characterised by rapid growth, tissue maturation, and organ function development rather than organogenesis; teratogens in this period cause growth restriction and functional impairment rather than structural malformations.

The volume of air remaining in the lungs after a normal tidal expiration; decreases ~20% in pregnancy due to diaphragmatic elevation by the gravid uterus, reducing oxygen reserves.

A spectrum of conditions arising from abnormal trophoblastic proliferation, including hydatidiform mole (partial and complete), invasive mole, choriocarcinoma, and placental-site trophoblastic tumour; associated with markedly elevated hCG and uterus larger than dates.

The rate at which the kidneys filter blood; increases 40–60% in pregnancy, lowering serum creatinine to 0.4–0.6 mg/dL (the pregnancy-normal range).

Softening of the cervix from its normal firm consistency (tip of the nose) to a softer consistency (lips of the mouth), occurring from approximately 6–8 weeks of pregnancy; a probable sign.

The mature, dominant ovarian follicle (~18–24 mm) that develops from the selected cohort under FSH stimulation; contains the oocyte surrounded by the cumulus oophorus within a large fluid-filled antrum.

Extreme softening of the isthmus (lower uterine segment) detectable on bimanual examination at 6–8 weeks of pregnancy, such that the cervix and uterine body appear almost disconnected; a probable sign of pregnancy.

5 mg/day of folic acid, recommended pre-conceptionally and in the first trimester for women with risk factors for NTD: previous NTD-affected pregnancy, diabetes, all epilepsy, BMI >30, malabsorption. Standard dose (400 mcg/day) is insufficient for these groups.

A false-negative immunoassay result caused by extremely high levels of the target analyte (hCG) saturating both capture and detection antibodies without forming a sandwich — relevant in gestational trophoblastic disease; excluded by diluting the sample 1:10 and retesting.

A glycoprotein hormone produced by the syncytiotrophoblast from implantation; rescues the corpus luteum to maintain progesterone production in early pregnancy; peaks at 10–12 weeks of gestation; basis of all pregnancy tests.

A polypeptide hormone produced by the syncytiotrophoblast that acts as an insulin antagonist, promoting maternal lipolysis and sparing glucose for fetal use; the primary driver of gestational insulin resistance; levels rise progressively through pregnancy.

Physiological dilation of the ureters in pregnancy, more marked on the right, due to progesterone-mediated smooth muscle relaxation and mechanical compression by the gravid uterus; predisposes to urinary tract infections.

A pro-thrombotic state characterised by increased fibrinogen (4–6 g/L), elevated factors VII, VIII, X, and reduced protein S; adaptive for limiting haemorrhage at delivery but conferring 5–10× increased VTE risk.

The pre-conception period during which live attenuated vaccines (MMR, varicella) must be administered — at least 1 month before conception attempts — because they are contraindicated during pregnancy due to theoretical risk of fetal infection.

The narrow period of endometrial receptivity (approximately cycle days 20–24 in a 28-day cycle; days 6–10 post-fertilisation) during which the blastocyst can successfully adhere to and invade the endometrium; outside this window the endometrium is refractory.

The funnel-shaped distal end of the fallopian tube, bearing ~25 fimbriae that sweep the ovulated ovum into the tube; the fimbria ovarica attaches to the ovary.

The primary growth hormone-independent anabolic hormone driving fetal growth in the second and third trimesters, produced in virtually all fetal tissues; circulating IGF-1 levels correlate strongly with birth weight and are low in IUGR.

The maternal blood-filled space surrounding the chorionic villi in the placenta; receives blood from spiral arteries and drains into uterine veins; the site of gas, nutrient, and waste exchange.

The 0.5 cm narrow constriction between the uterine body and the cervix; becomes the lower uterine segment in late pregnancy, the site of lower-segment caesarean section.

The primary muscular diaphragm of the pelvis, comprising pubococcygeus, iliococcygeus, and puborectalis; supports the pelvic viscera and maintains the closed urogenital hiatus.

The mid-cycle peak of luteinising hormone secretion, triggered by the positive feedback of peak oestradiol from the dominant follicle; triggers ovulation approximately 36 hours after onset and resumes meiosis I in the primary oocyte.

A fractionated heparin anticoagulant that does NOT cross the placenta, making it the preferred anticoagulant throughout pregnancy; used as a substitute for warfarin (which does cross the placenta and is teratogenic) once pregnancy is confirmed or planned.

The transition, occurring at approximately 8–10 weeks of gestation, during which progesterone production shifts from the corpus luteum of the ovary to the placenta as the dominant source; failure of this shift leads to early pregnancy loss.

Hypertrophic sebaceous glands on the areola that become prominent from 8 weeks of pregnancy; secrete a lubricating, bacteriostatic fluid protecting the nipple during breastfeeding.

A thick mucous secretion that fills the endocervical canal during pregnancy, providing a physical and immunological barrier to ascending infection; its expulsion near term ('show') signals cervical preparation for labour.

An immunosuppressant used in SLE and renal transplant rejection; teratogenic (fetal ear and limb abnormalities, facial clefts, cardiac defects) — must be discontinued at least 6 weeks before conception and substituted with azathioprine.

The thick middle smooth muscle layer of the uterine wall, responsible for labour contractions and post-delivery haemostasis via compression of spiral arteries.

A formula for calculating the expected date of delivery: EDD = LMP − 3 calendar months + 7 days; assumes a regular 28-day cycle with ovulation on day 14; adjustments needed for cycles of different length.

A congenital malformation resulting from failure of neural tube closure by day 28 post-fertilisation; includes anencephaly (cranial) and spina bifida (spinal); risk reduced by ~70% with periconceptional folic acid supplementation.

The process of female gamete production from oogonia through meiosis; characterised by arrest in prophase I from birth until the LH surge resumes meiosis I, and re-arrest at metaphase II until sperm penetration; each primary oocyte yields one functional ovum and two polar bodies.

The embryonic period of major organ formation, occurring between weeks 3–8 of embryonic life (weeks 5–10 of the last menstrual period); exposure to teratogens during this window causes structural malformations.

The outermost serosal (peritoneal) layer of the uterine wall.

A dilutional fall in haemoglobin concentration due to plasma volume expanding (~50%) proportionally more than red cell mass (~25%) — not a deficiency state; haemoglobin should remain ≥11 g/dL (WHO).

Glucose in the urine despite normal blood glucose in pregnancy, resulting from increased GFR exceeding tubular reabsorptive capacity; does not diagnose gestational diabetes.

Abnormal placentation in which placental villi adhere to (accreta), invade into (increta), or penetrate through (percreta) the myometrium; caused by deficient decidua basalis, most commonly in the context of a prior caesarean scar.

Fertilisation of an oocyte by more than one spermatozoon, resulting in a triploid (69 chromosomes) embryo incompatible with normal development; prevented primarily by the cortical reaction.

Definitive findings that confirm the presence of a living fetus; include fetal cardiac activity on ultrasound, fetal movements felt by the examiner, and fetal heart sounds audible by Doppler from ~10–12 weeks.

The recto-uterine pouch — the deepest and most dependent recess of the peritoneal cavity in the erect posture, bounded by the posterior uterus/cervix anteriorly and the rectum posteriorly; site of fluid, blood, and pus accumulation.

A structured clinical consultation offered before planned pregnancy to identify and modify maternal risk factors — medical, pharmacological, nutritional, immunological — that could harm the mother or developing embryo, ideally 3–6 months before conception.

Subjective symptoms reported by the patient that are consistent with pregnancy but not specific to it; include amenorrhoea, nausea, breast tenderness, urinary frequency, and quickening.

The dormant resting unit in the ovary, consisting of a primary oocyte arrested in diplotene of meiotic prophase I surrounded by a single layer of flattened granulosa cells; the pool (about 400,000 at puberty) represents the entire reproductive potential of the ovary.

Objective clinical findings on examination that strongly suggest pregnancy but are not definitive; include uterine enlargement, Hegar's sign, Chadwick's sign, Goodell's sign, ballottement, and Braxton Hicks contractions.

The dominant hormone of pregnancy physiology: smooth muscle relaxant (uterine quiescence, LOS, constipation, ureteral dilation), respiratory stimulant (↑TV, respiratory alkalosis), and immunological mediator of fetal tolerance.

The first fetal movements perceived by the mother — typically at 18–20 weeks in primigravidae and 16–18 weeks in multigravidae; a presumptive symptom of pregnancy (subjective).

A polypeptide hormone from the corpus luteum and placenta that softens pelvic ligaments and symphysis, reduces uterine contractility, and contributes to renal vasodilation and early GFR rise.

A state of low PaCO₂ (~30–32 mmHg) and mildly elevated pH (~7.44) resulting from progesterone-driven hyperventilation; compensated by renal bicarbonate excretion (HCO₃⁻ ~18–22 mEq/L).

A validated scoring tool for measuring systemic lupus erythematosus disease activity; a score of ≤4 indicates remission, which should be sustained for at least 6 months before conception to optimise pregnancy outcomes.

The continuous production of spermatozoa from spermatogonia in the seminiferous tubules from puberty onwards; each primary spermatocyte yields four functional spermatozoa via two equal meiotic divisions followed by spermiogenesis; takes approximately 74 days.

The characteristic thread-like stretchability of mid-cycle cervical mucus under oestrogen stimulation; can be drawn into a thread 10–15 cm long at ovulation; a marker of the fertile window (also used in natural family planning).

The physiological process in early pregnancy by which invasive cytotrophoblast cells transform maternal spiral arteries from muscular, high-resistance vessels into wide, low-resistance conduits; failure of this process is the primary pathological event in pre-eclampsia and placenta-based IUGR.

The infundibulopelvic ligament — a peritoneal fold from the lateral pelvic wall to the ovary, containing the ovarian vessels, lymphatics, and nerves.

The outer multinucleated, non-cellular layer of the chorionic villi formed by fusion of cytotrophoblast cells; responsible for placental hormone secretion and invasive implantation; the principal interface with maternal blood in the intervillous space.

The resistance offered by the peripheral vasculature to blood flow; falls 20–30% in pregnancy due to progesterone-mediated vasodilation and the low-resistance uteroplacental bed.

Any agent — drug, chemical, infection, radiation, or metabolic condition — that causes structural or functional abnormalities in a developing embryo or fetus during critical developmental periods.

The area of the cervix where columnar endocervical epithelium meets squamous ectocervical epithelium; the origin of virtually all cervical carcinomas and the target of the Pap smear.

The outer epithelial layer of the blastocyst that gives rise to the placenta; differentiates into cytotrophoblast and syncytiotrophoblast after implantation.

The main blood supply to the uterus, arising from the anterior division of the internal iliac artery; crosses above the ureter 1–2 cm lateral to the cervix ('water under the bridge').

The recess formed between the vaginal wall and the protruding cervix; four fornices — anterior, posterior, and two lateral. The posterior fornix is deepest and borders the Pouch of Douglas.

Sodium valproate is associated with ~10% risk of major congenital malformations (cardiac, NTDs, facial, limb) and 30–40% risk of neurodevelopmental problems (autism, intellectual disability) when used during pregnancy; the highest teratogenic risk of any anticonvulsant.

The cleft between the labia minora into which the urethral meatus, vaginal orifice, and Bartholin's gland ducts open.

The collective term for the external female genitalia, including the mons pubis, labia majora and minora, clitoris, vestibule, and associated glands.

The gelatinous myxoid connective tissue surrounding the two umbilical arteries and one umbilical vein within the umbilical cord, providing mechanical protection against cord compression.

A four-category risk stratification (Class I–IV) for pregnancy in women with cardiac disease; Class IV (including Eisenmenger's syndrome, severe pulmonary hypertension, severe LV dysfunction EF <30%) carries >25% maternal mortality risk and is a contraindication to pregnancy.

The diploid cell formed by fertilisation of a haploid oocyte by a haploid spermatozoon; the starting point of a new individual.