• Hatched blastocyst adheres to gland opening on wall of uterus, and triggers decidual reaction
• Endometrial stroma becomes edematous and high vascular
• Downregulation of uterine mucins to allow attacment of HSPG (embryo) to HS binding site 
• Penetration of epithelium and breakdown of basal lamina
• Syncytiotrophoblast formed 
• Formation of trophobastic lacunae within syncutriotrophoblast

• 1y villi - defined cytotrophoblastic projections convered by syncytiotrophoblast
• 2y villi - mesenchymal core within cytotrophoblast, syncytiotrophoblast on surface
• 3y villi - mesenchyme invaded by fetal blood cells
• Formation of cytothrophoblast shell, anchoring villi and substantial villi branching
• Mature villi - very branched, outer syncytiotrophoblast, incomplete cytotrophoblast layer, fetal blood vessels contiguous within syncytiotrophoblast, loose mesenchyme containing scattered phagocytes 

• Placental intervillous space receive blood from branches of umbilical arteries (from internal iliac) and carry deoxygenated blood. Oxygen, nutrient rich venous blood from placenta passes via umbilical vein to liver and to right atrium
• Countercurrent flow in intervillous soace ensure maximal transfer
• Blood leaves intervillous spaces via uterine vein
• Uterine contractions forces blood into intervillous space, then relaxation allows opening of veins and release of intervillous pressure
• Simple diffusion transfer of small molecules, unconjugated non-polar molecules, water, eletrolytes, urea, cholesterol and gases
• Carrier mechanisms involving specific receptors - immunoglobulins, Fe, Ca, Cu, glucose, vit B12, folate, riboflavin, vit C, amino acids, some hormomes

• hCG preserves corpus luteum and signals pregnancy
• Maintainence of pregnancy - progesterone maintain uterine quiescence, oestradiol for uterine growth
• Maternal metabolism - hPL (similar to GH or PRL) increases lipid breakdown and energy generation
• Preperation for parturition - oestradiol induces contraction associated proteins by myometrium, stimulates production of oxytocin receptor, increases myometrial excitibility. Placental CRH appears to act as parturition readiness signal
• Myometrial contractions and modification of cervix- PGE₂ and PGF_2α (earlier pregnancy, relaxant PGI₂ predominates)
• Preparation for lactation - oestradial stimulates development of mammary duct system, progesterone causes alveoli development, hPL has lactogenic effect (during pregnancy, milk production inhibited by progesterone and oestradiol)

• Suckling stimulates paraventricular nuclei of supraoptic nucleus of hypothalamus, signalling the pituitary gland to produce oxytocin
• Oxytocin stimulates contraction of myoepithelial cells surrounding alveoli causing flow through duct system and milk release through nipple
• Mechanism can become conditioned (crying) by higher brain centres

Contraception methods

• Pill - combined prevents ovulation by action at pituitary and thickens cervical mucus, progestin-only pill thickens cervical mucus but less effect on ovulation, progestin injection has stronger effect on prevention of ovulation
• Intrauterine devices are copper containing as well as plastic impregnated with progesterone receptor modulator
• Oviduct can be banded, cauterised or tied and cut
• Female condom, vaginal ring with progesterone receptor modulator
• Anti-ZP antibodies, anti-hCG antibdies
• Male - ligation of epididymis, condom

Fertility treatment

(men and women)

• Female  - pulsed GnRH to restore fertility in Kallman's females, use of FSH and LH, gamete/zygote intrafallopian tube injection, IVF, cryoprotection of gametes
• Male - FSH and LH to restore fertility (can't use testosterone as dose is too high), cyoprotection of semen, intratesticular injection of spermatogonia, intra-cytoplasmic sperm injection