Pregnancy — Symptoms, Causes & Treatment | MyMedicPlus

Pregnancy is a normal physiological process lasting approximately 40 weeks (280 days) from the last menstrual period, divided into three trimesters: first (weeks 1–12), second (weeks 13–27), and third (weeks 28–40). Fertilisation of an ovum by a sperm in the fallopian tube produces a zygote, which implants in the uterine endometrium at approximately 6–10 days. Placentation (development of the placenta) provides fetal nutrition, gas exchange, and hormone production — notably human chorionic gonadotrophin (hCG — the hormone detected in pregnancy tests), progesterone (maintains the endometrium and suppresses uterine contractions), and oestrogen (drives breast development and uterine growth). Major physiological adaptations include: blood volume expansion by 40–50% (requiring increased red cell mass — hence iron and folate demands), cardiac output increase of 30–50%, reduced blood pressure in the first and second trimester from decreased systemic vascular resistance, GFR increase of 50% (affecting drug dosing and renal thresholds), hypercoagulable state (VTE risk elevated 5-fold — peaks postpartum), and respiratory changes (diaphragm elevation, progesterone-driven increased tidal volume and respiratory rate, PaCO2 decreases). Understanding pregnancy physiology is essential for interpreting blood tests, dosing medications, and recognising pathological deviations.

Pregnancy results from fertilisation of an ovum by a sperm cell, typically in the fallopian tube, followed by implantation of the blastocyst in the uterine endometrium. Risk factors that increase the probability of pregnancy complications: advanced maternal age (above 35 — increased chromosomal abnormalities, pre-eclampsia, placenta praevia, and stillbirth risk), obesity (BMI above 30 — gestational diabetes, pre-eclampsia, macrosomia, operative delivery, and thromboembolism risks are all substantially elevated), hypertension (pre-existing hypertension elevates superimposed pre-eclampsia risk), pre-existing type 1 or type 2 diabetes (congenital anomalies up to 2–5 times baseline rate if HbA1c above 48 mmol/mol at conception, macrosomia, stillbirth), smoking (IUGR, placental abruption, premature birth — dose-dependent), multiple gestation (twins — 50% deliver preterm; triplets — 90% deliver preterm; TTTS in monochorionic twins), prior adverse outcomes (previous stillbirth increases recurrence risk 2–10-fold; previous ectopic increases recurrence risk 10–15%), chronic kidney disease, autoimmune conditions (SLE — pre-eclampsia, neonatal lupus), antiphospholipid syndrome, and thrombophilias. First pregnancy (nulliparity) carries higher pre-eclampsia risk than subsequent pregnancies.

Early signs (first trimester, weeks 1–12): missed period (most common first symptom), nausea and vomiting (morning sickness — affects 70–80% of pregnant women; typically begins at 6 weeks, peaks at 8–10 weeks, and resolves by 14 weeks in most; hyperemesis gravidarum — severe persistent vomiting requiring IV rehydration affects 0.5–2%), breast tenderness and enlargement, nipple darkening and areolar enlargement, increased urinary frequency (rising hCG stimulates bladder, and the growing uterus compresses it by 10–12 weeks), fatigue (progesterone-driven — often severe in the first trimester), heightened sense of smell and food aversions, mild pelvic cramping (implantation cramping — normal), and light implantation bleeding (brown spotting at 6–8 days post-conception). Second trimester (weeks 13–27): nausea usually improves; fetal movements first felt (quickening — typically 18–22 weeks in first-time mothers, earlier in subsequent pregnancies); round ligament pain from uterine stretching; increased appetite; nasal congestion; skin changes (linea nigra, chloasma, stretch marks). Third trimester (weeks 28–40): significant abdominal growth, Braxton-Hicks contractions (painless practice contractions — distinguished from true labour by being irregular and not strengthening), back pain (from ligamentous laxity and postural changes), heartburn (from hiatal acid reflux — uterus displaces stomach), ankle oedema (normal physiological oedema from venous compression), shortness of breath (from diaphragm elevation), and increased fetal movements that should be monitored daily after 28 weeks.

Urine hCG test (home pregnancy test — detects beta-hCG from approximately 10–14 days post-conception, a few days before the missed period); serum beta-hCG (blood test — more sensitive, used to confirm and quantify hCG for monitoring ectopic pregnancy or miscarriage). Booking appointment (8–10 weeks): full blood count (FBC — anaemia, thrombocytopaenia), blood group and antibody screen (Rh status for anti-D prophylaxis planning), rubella IgG (immunity check), syphilis serology, HIV test, hepatitis B surface antigen, haemoglobin electrophoresis (sickle cell and thalassaemia carrier screening), and midstream urine culture (asymptomatic bacteriuria — requires treatment to prevent pyelonephritis and preterm birth). First trimester combined screening (11–14 weeks): nuchal translucency ultrasound + serum PAPP-A + free beta-hCG — screens for trisomies 21 (Down), 18 (Edwards), and 13 (Patau); detection rate approximately 90%. Non-invasive prenatal testing (NIPT) — cell-free fetal DNA from maternal blood — higher sensitivity (>99% for trisomy 21); offered to higher-risk women or as opt-in additional screening in many health systems. Dating scan (11–14 weeks): establishes gestational age and estimated due date by crown-rump length (CRL). Fetal anomaly ultrasound (18–21 weeks): detailed structural survey of all organ systems; detects approximately 50% of structural anomalies. Third trimester growth scans (26–34 weeks in high-risk pregnancies): assess fetal growth, liquor volume, and placental position.

Antenatal care (ANC): regular structured prenatal visits monitor maternal and fetal wellbeing, screen for complications, and provide health education. The NICE schedule for low-risk nulliparous women involves 10 appointments; multiparous women with uncomplicated pregnancies have 7. Each appointment serves a specific surveillance purpose: blood pressure and urine dipstick testing (pre-eclampsia screening), symphysis-fundal height measurement (IUGR detection), fetal position assessment from 36 weeks, and review of fetal movements. Nutritional supplementation: folic acid 400 mcg daily (5 mg for high-risk women — previous neural tube defect, anticonvulsant use, diabetes, BMI above 30) from pre-conception through the first 12 weeks (reduces neural tube defect risk by 70%); vitamin D 10 mcg (400 IU) daily throughout pregnancy and breastfeeding; iron (only if iron-deficiency anaemia confirmed on CBC); iodine (150 mcg daily — adequate iodine intake is essential for fetal thyroid development and neurological outcomes). Avoidance: alcohol (no safe limit — fetal alcohol spectrum disorder affects cognition, behaviour, and growth); smoking (IUGR, placental abruption, premature birth); teratogens (ACE inhibitors, ARBs, valproate, retinoids, methotrexate, warfarin — review and switch all medications before conception where possible); listeria-risk foods (unpasteurised dairy, soft cheeses, deli meats, pâté); raw or undercooked meat and eggs (toxoplasmosis and Salmonella risk); excess vitamin A (liver, liver pâté — teratogenic). Aspirin 150 mg nightly from 12 weeks for women at high pre-eclampsia risk (reduces risk by up to 62%). Vaccination: influenza vaccine (recommended in all trimesters), whooping cough (pertussis/Tdap) vaccine at 16–32 weeks (protects newborn before their first vaccination at 8 weeks).

Potential complications across the pregnancy and postpartum continuum: First trimester — miscarriage (10–20% of clinically recognised pregnancies), ectopic pregnancy (1–2% — a life-threatening emergency), hyperemesis gravidarum (0.5–2% — severe vomiting requiring hospitalisation and IV rehydration), and threatened miscarriage (vaginal bleeding with a viable intrauterine pregnancy). Second and third trimester — gestational diabetes (6–9% of UK pregnancies — macrosomia, shoulder dystocia, increased caesarean rate; predicts type 2 diabetes risk), pre-eclampsia (2–8% — characterised by new hypertension and proteinuria or end-organ dysfunction after 20 weeks; severe forms cause eclampsia/seizures and HELLP syndrome — haemolysis, elevated liver enzymes, low platelets), placenta praevia (low-lying placenta covering the cervical os — requires elective caesarean), placental abruption (premature separation — painful haemorrhage, fetal distress), PPROM (preterm prelabour rupture of membranes — infection and preterm delivery risk), and IUGR (growth restriction — risk of fetal hypoxia and stillbirth). Stillbirth affects approximately 1 in 200 UK pregnancies — higher risk with advanced maternal age, obesity, reduced fetal movements, post-dates pregnancy, and multiple pregnancy. Postpartum — PPH (postpartum haemorrhage — the leading cause of maternal mortality globally), puerperal sepsis, venous thromboembolism, and postpartum depression (10–15% of mothers). Regular antenatal monitoring allows early detection and prompt management to reduce maternal and fetal risks.

Preconception care is the most important intervention for optimising pregnancy outcomes — ideally beginning 3–6 months before conception: achieve healthy BMI (18.5–29.9 — obesity significantly elevates risks of GDM, pre-eclampsia, macrosomia, operative delivery, and congenital anomalies); start folic acid 400 mcg daily (at least 1 month before conception); review all medications for teratogenicity with a GP or specialist (sodium valproate — pregnancy prevention programme mandatory; ACE inhibitors and ARBs — switch to labetalol or methyldopa; methotrexate — stop 3 months before conception; retinoids — stop 1 month before conception); manage chronic conditions (optimise diabetes control to HbA1c below 48 mmol/mol before conception to reduce congenital anomaly risk by 70%; achieve thyroid hormone normalisation in hypothyroidism; optimise epilepsy management with the safest antiepileptic); achieve rubella immunity (check serology; live vaccine contraindicated in pregnancy — vaccinate before conception); cervical smear up to date; discuss weight, alcohol, and smoking cessation. During pregnancy: attend all scheduled antenatal appointments (each serves a specific screening and monitoring purpose — missing appointments increases risk of undetected complications); respond promptly to any warning symptoms listed in the when-to-see section; maintain moderate physical activity (150 minutes per week — reduces GDM, pre-eclampsia risk, and promotes healthy birth weight); influenza vaccine and Tdap (whooping cough) vaccine at recommended gestational ages.

Call emergency services or go to A&E immediately for: heavy vaginal bleeding at any stage of pregnancy; severe abdominal or pelvic pain; severe headache with visual disturbance, sudden swelling of the face or hands, or epigastric pain after 20 weeks (signs of pre-eclampsia — a serious pregnancy complication); reduced or absent fetal movements after 28 weeks (contact your maternity unit the same day — do not wait until the next day); signs of early labour before 37 weeks (regular contractions, leaking fluid); one-sided lower abdominal pain in the first trimester (possible ectopic pregnancy — a life-threatening emergency). Book an appointment with your GP or midwife as soon as a pregnancy test is positive to register with antenatal care — the first booking appointment at 8–10 weeks establishes your care pathway and screens for risk factors. Seek urgent review if you develop: nausea and vomiting so severe you cannot keep any fluids down (hyperemesis gravidarum — may need IV rehydration); pain or burning on urination (urinary tract infection — treat promptly to prevent preterm birth); signs of deep vein thrombosis (calf pain, swelling, redness — pregnancy is a high-risk state for thrombosis). Women with pre-existing conditions (diabetes, hypertension, heart disease, epilepsy, thyroid disease) should see their specialist before or early in pregnancy to adjust medications and monitoring.