Related by context. All words. (Click for frequent words.) 59 invitro fertilization 57 IVF ICSI 57 Intra Cytoplasmic Sperm Injection 57 Indira Hinduja 56 cumulus removal 56 oocyte retrieval 56 Vitro Fertilisation IVF 56 IVF 56 Vitro fertilization 55 fertilized ova 55 Attain IVF Programs 54 GIVF 54 implanted embryos 54 invitro 54 Octuplets mom identifies 54 oocyte cryopreservation 54 Vitro Fertilization IVF 54 donor gametes 54 vitro fertilization IVF 53 Preimplantation Genetic Diagnosis PGD 53 intrauterine insemination IUI 53 ovulation induction 53 frozen embryos implanted 53 INVO procedure 53 hysteroscopy 53 intra cytoplasmic sperm 53 gynaecologic 53 oocyte donation 53 preimplantation genetic diagnosis PGD 53 IN VITRO 52 spontaneously aborted 52 gynae 52 Depo Provera injections 52 embyros 52 Bone marrow transplant 52 umbilical stem cells 52 Pre implantation genetic 52 IVF treatment 52 IUI 52 Dr Nayna Patel 52 Vitro Fertilisation 52 obstetrical complications 52 vitro fertilization 52 intracytoplasmic sperm injection 52 egg retrieval 52 Mohamed Taranissi 52 eSET 52 octuplets conceived 52 vitro maturation IVM 52 IVF embryo 51 pancreatic ductal 51 tubal reversal 51 caesarean section births 51 breech births 51 infertile couples conceive 51 intra uterine insemination 51 Vitro Fertilization 51 Verlinsky 51 Dr Taranissi 50 ABO incompatible 50 intracavitary 50 intracytoplasmic sperm injection ICSI 50 surfactant therapy 50 recombinant FSH 50 Fertility clinics 50 laparoscopic nephrectomy 50 Geoffrey Sher 50 IVF treatments 50 Assisted reproductive 50 treating uterine fibroids 50 embryos fertilized 50 infertile couples 50 MENOPUR 50 vitro maturation 50 Donated organs 50 cesarean section deliveries 50 Scorch marks infused 50 thalassaemic 50 drug clomiphene 50 tubal ligation reversal 50 cryo preservation 50 Caesarian sections 50 cervical cerclage 50 FERTILITY 50 abdominal ultrasounds 49 neo natal ICU 49 Taranissi 49 intra uterine insemination IUI 49 sperms 49 nipples testicles scrotum 49 zygotes 49 uterus fallopian tubes 49 stillborn infants 49 sperm cryopreservation 49 Male infertility 49 anencephalic 49 heel prick test 49 Surrogate mothers 49 miscarriages stillbirths 49 uncomplicated pregnancies 49 tubectomy 49 aneuploidy screening 49 IUD inserted 49 Umbilical cord 49 hysteroscopic sterilization 49 Donor Egg 49 PGD PGS 49 Kathy Giusti myeloma 49 gyn 49 speculums 49 oocytes eggs 49 mature oocytes 49 artery embolization 49 preimplantation genetic diagnosis 49 ICSI cycles 49 Northridge Moschella 49 reusing needles 48 membrane rupture 48 intrauterine insemination 48 unexplained infertility 48 RhD negative 48 Infertile couples 48 embryologists 48 vasectomy reversal 48 dialyses 48 cryopreserved embryos 48 bone allografts 48 gestational surrogates 48 Expectant mums 48 ante partum 48 peri natal 48 RMACT 48 StemLifeLine 48 Peritoneal dialysis 48 pituitary disorders 48 prenatal postpartum 48 Breastfeeding moms 48 Preimplantation genetic diagnosis 48 invasive biopsy 48 Synchrony lens 48 vitro fertilization treatments 48 administer intraoperative radiation 48 nasal ointment 48 maternities 48 embryo cryopreservation 48 Anti Retroviral Treatment 48 ovaries uterus 48 Bone marrow transplantation 48 singleton pregnancy 48 fetuses aborted 48 embryo transfers 48 Kailas Gheewala 48 extra corporeal membrane 48 Intrauterine devices 48 Kaival Hospital matches 48 lacto 48 hMG 48 dress skimpily 48 scalpel vasectomy 48 My Binky Baby 48 midwives doulas 48 extracorporeal membrane oxygenation ECMO 47 periodontal gum 47 multiple gestations 47 intra uterine devices 47 donor liver transplantation 47 ovarian hyperstimulation syndrome OHSS 47 preimplantation genetic screening 47 reproductive endocrine 47 Dr. K. Muhunthan 47 Attain IVF Program 47 kidney liver pancreas 47 laparoscopes 47 pessaries 47 embryo implantation 47 radiology pathology 47 spontaneous vaginal 47 Counsyl 47 Embryo mix 47 muscle dystrophies 47 gastroscopy 47 uterine fibroid tumors 47 IVF PGD 47 recombinant follicle stimulating 47 hormone FSH 47 engineered bladders 47 Hysterectomies 47 Gary Onufer 47 pediatrics obstetrics 47 Organ transplants 47 steriliser 47 transfuse blood 47 Mr Taranissi 47 IVF Clinic 47 therapeutic apheresis 47 babys 47 transfusion syndrome 47 Octuplet mom fears 47 transcervical 47 ICSI intracytoplasmic sperm 47 post partum haemorrhage 47 fertility treatments 47 gastroenterology obstetrics gynecology 47 reimplantation 47 orchiectomy 47 facial rejuvenation procedures 47 acupuncture hypnosis 47 ovarian stimulation 47 Dr. Zev Rosenwaks 47 ovary uterus 47 Dr. Leondires 47 antenatal screening 47 infant circumcision 47 abort fetuses 47 placental tissue 47 unfertilised eggs 47 cancerous ovary 47 preimplantation genetic 47 IVF clinics 47 Ella Milbank Foshay 47 thymectomy 47 prenatal massage 47 IM progesterone 47 colon resection 47 infertility miscarriage 47 intravascular catheters 47 cryopreserved 47 nevirapine regimen 47 fetal ultrasound 47 infertility 47 elective Caesarean section 47 neuter spay 47 inseminations 47 Sean Boutros 47 breech babies 47 donor insemination 47 untrained midwives 46 Gestational age 46 Magnesium sulfate 46 gynecological surgeries 46 radiology cardiology 46 implantation genetic 46 Blood transfusion 46 keratoplasty 46 premies 46 Sedation dentistry 46 reproductive endocrinologist 46 corifollitropin alfa 46 cryogenic preservation 46 Ante natal 46 Certified Nurse Midwives 46 rFSH 46 testicular biopsy 46 recanalisation 46 HIPEC 46 preemie babies 46 Dr. Ourian 46 undergoing IVF 46 percutaneous drainage 46 small keyhole incisions 46 Lactation consultants 46 IVD sperm 46 SIRM 46 immunologically compatible 46 secondary amenorrhea 46 Airboats evacuated 46 immunosuppression therapy 46 pap smears mammograms 46 birthing 46 savior sibling 46 elective caesarean section 46 endermologie 46 noninvasive outpatient 46 immunologically matched 46 vitro fertilization artificial insemination 46 Colon hydrotherapy 46 liver grafts 46 Ob gyns 46 birthing kits 46 frozen IVF embryos 46 ProLipo 46 bone marrow aspiration 46 Assisted Reproductive 46 multi incision laparoscopic 46 RhD 46 epidural anesthesia 46 screenings immunizations 46 hypoxic ischemic encephalopathy HIE 46 sonographically guided 46 Nurse midwives 46 haematologists 46 drugless 46 Gab Kovacs 46 pancreatic resection 46 cryosurgery freezing 46 Hoerstrup 46 totipotent 46 reproductive tract infections 46 Shingles vaccine 46 Endometrial ablation 46 obstetric gynecological 46 allograft tissue 46 doctor Severino Antinori 46 caesarian deliveries 46 livers kidneys 46 broom cupboards 46 stem cells harvested 46 vaccinated dewormed 46 SEQureDx ™ 46 gauze syringes 46 Blastocysts 46 PrepaCyte CB 46 diaper feminine napkin 46 electively 46 elective caesarean 46 CT fluoroscopy 46 Artificial insemination 46 egg retrievals 46 prenatal diagnostic 46 umbilical cord stem cells 46 preimplantation 46 Islet cell 46 urine dipstick 46 Suzi Leather 46 distraction osteogenesis 46 pediatricians obstetricians 46 placental malaria 46 induce ovulation 46 embryonic tissue 46 antral follicles 46 Artificial pancreas 46 Mater Mothers 46 contraception sterilization 46 laser lipo 46 ovarian transplant 46 fertilising eggs 46 needle phobic 46 renal transplants 46 INVOcell device 46 Abdominal ultrasound 46 cadaveric donor 45 fetal heartbeats 45 hormone human chorionic 45 vitro Fertilization 45 HBsAg positive 45 oncoplastic 45 conceptus 45 IVF cycles 45 Pneumonia vaccine 45 preeclamptic 45 transplants CBTs 45 Restalyne 45 Anurag Bishnoi 45 Board probes octuplet 45 Sperm donors 45 artificial insemination AI 45 umbilical stem cell 45 Amniocentesis 45 hypoallergenic formula 45 prevent reinfection 45 stereotactic biopsy 45 neonatal ward 45 removed laparoscopically 45 hypnobirthing 45 postnatal 45 elective cesarean section 45 neonatal circumcision 45 pre natal 45 transabdominal 45 gynecologic procedures 45 tubal sterilization 45 Hematopoietic stem cell 45 laproscopic 45 loop electrosurgical excision 45 aspirators 45 cryogenically preserve 45 fertilized embryo 45 elective Caesarean 45 operates www.integramed.com leading 45 assisted reproduction 45 Innermost Secrets 45 Tu Du 45 fetal fibronectin test 45 hcg 45 transfusing blood 45 cryo preserved 45 body contouring procedure 45 prophy 45 polycystic 45 MRIs X rays 45 Unborn babies 45 saline infusion 45 penis vagina breast 45 minimally invasive endoscopic 45 thoracoscopy 45 Ramses II mummy 45 osteochondral 45 ovary tissue 45 placental stem cells 45 undergone fertility treatments 45 Emad Darwish 45 Allogeneic 45 PCOD 45 babies 45 genitourinary medicine 45 bath emollients 45 Liver transplant 45 embryo clones 45 prenatal diagnosis 45 pluripotent embryonic 45 gooey amyloid 45 Umbilical cord stem cells 45 DuoFertility 45 CBCT scanner 45 tumescent liposuction 45 Essure ® 45 eyelash transplant 45 morally licit 45 vaginal vault 45 ovarian hyperstimulation 45 amniotic cavity 45 Liver transplantation 45 assisted reproductive 45 vasectomy reversals 45 Official canadian pharmacy 45 severely immunocompromised patients 45 caesarian birth 45 inhibiting ovulation 45 gynecological procedures 45 ultrasonic scalers 45 INVO Bioscience 45 uterus womb 45 IDET procedure 45 pheresis 45 Nayana Patel 45 cloned primate 45 refore 45 phaco emulsification 45 stem cell engraftment 45 transvaginal sonography 45 ovulatory 45 VCUG 45 Botox collagen 45 uterine cervix 45 endoscopic retrograde cholangiopancreatography ERCGrant Parpan 45 ductal lavage 45 colostrums 45 Follicle Stimulating Hormone 45 puerperal sepsis 45 reduction mammoplasty 45 Adaptive Radiation Therapy 45 oophorectomy removal 45 bottle nipples 45 autologous fat 45 antisepsis 45 Cryopreservation 45 vivo pharmacology services 45 oocyte egg 45 mommy makeovers 45 Accelerated Partial Breast Irradiation 45 implanting Nadya Suleman 45 detergents wastewater 44 myoma 44 uterus transplants 44 fetal fibronectin 44 Islet transplantation 44 dermatologically tested 44 sacrocolpopexy 44 ultrasonic liposuction 44 Minimally invasive procedures 44 anovulatory 44 Gary Ghiselli 44 fertilization clinics 44 gestational sac 44 bariatric surgical 44 PET CT scanning 44 invasive prenatal 44 spontaneous miscarriages 44 Sperm injection 44 aborted babies 44 Anna Taddio 44 ELBW infants 44 autologous tissue 44 pa tients 44 ovulation fertilization 44 transplanting kidneys 44 Reconstructive surgeon Dr. 44 Nadya Suleman NAH' dee 44 MHRA compliant 44 allogeneic hematopoietic stem cell 44 bone grafting procedures 44 addition RTI pastes 44 fertilized eggs implanted 44 placental tissues 44 gene expression Sapienza 44 blocked fallopian tubes 44 magnesium sulphate 44 cranial osteopathy 44 karyotyping 44 intra uterine device 44 IntegraMed fertility practice 44 intra dermal 44 stemcell 44 Clearant Process 44 transplanted livers 44 Tina Alster 44 colonscopy 44 DHEA supplementation 44 esophageal resection 44 medicine pediatrics obstetrics 44 lipo 44 microdissection 44 eggs fertilized 44 teeth bleaching 44 Added Tomtishen 44 SILS procedure 44 Ectopic pregnancy 44 unclean needles 44 implanting embryos 44 OHSU Doernbecher 44 growth restriction IUGR 44 Autologous stem cell 44 Bhateri Devi 44 fluoride varnishes 44 catheterisation 44 perinatology 44 sperm donor offspring 44 Diaper rash 44 radical hysterectomy 44 uterus cervix 44 laser liposuction 44 Umbilical cords 44 captive giant pandas 44 antireflux 44 unfertilised 44 cow's milk formula 44 fibroma 44 cell culturing 44 leukapheresis 44 thoracentesis 44 unused embryos 44 embryos 44 cervixes 44 Expectant moms 44 transplant co ordinators 44 knee arthroscopies prostate biopsies 44 Cumulase 44 HICKORY MUSEUM OF 44 Antenatal 44 Werker tested 44 hemo dialysis 44 fertilized egg splits 44 Ecmo 44 varicose vein removal 44 prenatal 44 injection ICSI 44 Vasectomy Reversal 44 ventouse 44 Down syndrome spina bifida 44 SynCardia temporary CardioWest 44 valve prosthesis 44 physical therapists chiropractors 44 intra uterine 44 ante natal 44 HRC Fertility 44 Nothing Wadden 44 Beverly Hills Liposculpture 44 urethral stricture 44 miscarried fetuses 44 tummy tuck liposuction 44 x rays MRIs 44 Yury Verlinsky 44 SpermCheck 44 miscarriages premature births 44 pulmonary hypoplasia 44 DXA scans 44 Shady Grove Fertility 44 reimplanting sperm producing 44 Cesarean sections 44 lutropin alfa 44 intravenous catheters 44 autologous SCT 44 discarded umbilical cords 44 Extracting stem cells 44 Cholecystectomy 44 Kidney transplants 44 intradermal delivery 44 cotrimoxazole 44 trimester ultrasound 44 artificial fertilization 44 mitts nail clippers 44 amoxil 44 ASRM 44 tubal 44 tubal ligations 44 xenograft implants 44 gyne 44 Phenylketonuria PKU 44 Rh factor 44 Embryo adoption 44 abnormal pap 44 dialed Ybarra 44 aneuploid 44 post natal 44 osteopathic manipulation 44 abdominal hysterectomy 44 Neonatal ICU 44 prenatal postnatal 44 leukoreduction 44 Francis Delmonico 44 Goldbeck Wood 44 relapsed ALL 44 cytomegalovirus retinitis 44 bronchoalveolar lavage 44 transplanting organs 44 acupuncture meditation 44 Hair follicles 44 medicalised 43 Infertile 43 spinal manipulations 43 transcatheter aortic valve implantation 43 adult incontinent surgical 43 gauge vitrectomy 43 endometrial biopsy 43 nephrectomies 43 Antiretroviral therapy 43 injection lipolysis 43 bacteremic 43 cervical prostate 43 vitro treatments 43 postnatal ward 43 transrectal ultrasound guided 43 ethically fraught 43 vitro 43 botox treatments 43 neutering deworming 43 artificial sphincter 43 disinfectant cleaners 43 intravenous hydration 43 neonatal wards 43 sterile needles 43 Inhaled nitric oxide 43 newborn infants 43 NovaSure procedure 43 Cetrotide 43 donor nephrectomy 43 Reproductive Ethics 43 venipuncture 43 imperforate anus 43 Simon Fishel 43 adipose tissue derived 43 woman ovulates 43 stimulate ovulation 43 fibroid tumor 43 sub cutaneous 43 Brucellosis causes 43 perinatal outcomes 43 chromosomally normal 43 Domasin 43 GBS colonization 43 endoluminal 43 Valcyte tablets 43 diagnosis PGD 43 Severino Antinori 43 Lipo Dissolve 43 cleft lip cleft palate 43 ovaries fallopian tubes 43 sperm retrieval 43 sperm donation 43 scalpel blades 43 autografts 43 noncancerous growths 43 autologous transplant 43 amniotic fluids 43 rectal palpation 43 GFCF diet 43 ovarian hyperstimulation syndrome 43 Vaginal Birth After 43 buttock implants 43 IVM 43 needle aspiration 43 tetanus vaccines 43 CARE Fertility 43 IV sedation 43 Zain Hashmi 43 balloon sinuplasty 43 nonembryonic 43 LifeCell Dx 43 Cetrotide R cetrorelix 43 guided percutaneous 43 noninvasive painless 43 Rebecca Bresnik meanwhile 43 medicine obstetrics gynecology 43 vitro fertilizations 43 gynecology ophthalmology 43 endometrial tissue 43 ovulatory cycles 43 perinatal morbidity 43 suppressing ovulation 43 hymen reconstruction 43 hypno birthing 43 Dr Allan Pacey 43 molar pregnancy 43 MUMS TO BE 43 Sertoli cells 43 cesarean birth 43 buffy coat 43 leftover embryos 43 sk n clinics 43 fetal chromosomal abnormalities 43 sterile disposable 43 Study Spacing 43 obstetricians midwives 43 Hashmis 43 cadaveric organ 43 periodontal defects 43 cadaver transplants 43 surgical resection cavity 43 4D ultrasound 43 NovaSure endometrial ablation 43 Ultrasonographic 43 Expectant fathers 43 panoramic x ray 43 Genito Urinary 43 ovarian torsion 43 trophoblasts 43 fine needle aspirate 43 lipo dissolve 43 Coronary artery bypass 43 nulliparous 43 hematopoietic progenitor cells 43 liver pancreas kidney 43 reimplant 43 Retrograde ejaculation 43 controlled ovarian stimulation 43 artificial inseminations 43 cesarian section 43 ear syringing 43 Uterine fibroid embolization 43 freeze amnio stem cells 43 colicky babies 43 penile implants 43 prenatally diagnosed 43 lumbar punctures 43 microsurgery techniques 43 cellular immunotherapy 43 periodontal therapy 43 caths 43 Premature Ovarian Failure 43 4D imaging 43 reinfusion 43 oncology orthopedics 43 cardiology orthopedics 43 clincs 43 preemptive analgesia 43 Gestational 43 mercury amalgams 43 distemper vaccinations 43 colostomies 43 spokesman Klaus Schwertner 43 Pre natal 43 radioiodine therapy 43 circumcised penis 43 minimally invasive arthroscopic 43 single incision laparoscopic 43 myelomeningocele 43 uterine perforation 43 adipose derived stem cell 43 catherization 43 Dr Sherman Silber 43 SCBU 43 urethral strictures 43 Insemination 43 STEEN Solution TM 43 diagnosed prenatally 43 LDRP 43 Dr. Loeken 43 TOGA procedure 43 Selphyl 43 intravaginal 43 cesarean births 43 underdeveloped kidneys 43 neo bladder 43 PillCam capsule endoscopy 43 pessary 43 abdominal ultrasound 43 vernix 43 Neonatologist 43 thawed fertilized 43 delaying childbearing 43 caesarean delivery 43 gynecologic surgery 43 fFN 43 Postnatal 43 mammoplasty 43 embryo 43 Waxenberg herself 43 Lumpectomy 43 unspecialised 43 microinjection 43 Polycystic 43 chronic Lyme 43 frozen thawed 43 VBAC vaginal birth 43 uterus hysterectomy 43 gynecologic surgeries 43 VolChat 43 Jana Jelinkova spokeswoman 43 Asome news 43 irregular ovulation 43 intrapartum 43 sonographic evaluation 43 transrectal 43 Hepatitis B vaccination 43 vaginal fluids 43 tumor angiogenesis inhibitors 43 AMOR IPAT 43 Certified nurse midwives 43 subfertile 43 islet isolation 43 BABIES 43 subfertility 43 Nic Annette Bening 43 CycleBeads 43 Evenflo recalls 43 sonographic diagnosis 43 necrotising enterocolitis 43 hydroxy vitamin D 43 operable breast cancer 43 embryo implanted 43 Monash IVF 43 Nasal irrigation 43 CLEARANT PROCESS R 43 RISUG 43 prenatal ultrasound 42 female hormone progesterone 42 James Grifo 42 Transurethral 42 DIEP flap 42 prevent hemolytic 42 Fertility Institutes 42 stem cell transplantations 42 prolapses 42 organizations OPOs 42 gastric imbrication 42 abnormal hematopoietic cells 42 BRAF gene mutations 42 methylation markers 42 embryologist 42 Prolacta Bioscience 42 dialyse 42 nutrient supplementation 42 ovary stimulating 42 BFHI 42 perinatally 42 whooping cough vaccines 42 tetanus immunization 42 euthyroid 42 insulin secreting islet cells 42 pre operatively 42 Balloon sinuplasty 42 IUGR 42 beds wheelchairs walkers 42 lactation rooms 42 undergo mastectomy 42 name Cetrotide R 42 Eric Kodish 42 Gynaecologist 42 colon rectal 42 caesarean deliveries 42 uterine prolapse 42 amniotic epithelial cells 42 intravenous rehydration 42 vitro fertilization clinics 42 unexplained stillbirth 42 Fertilized eggs 42 rotary vane pumps 42 Dr. Domanskis 42 anovulation 42 remove osseous structures 42 bioidentical hormone 42 fistula repair 42 hemolytic disease 42 surplus IVF embryos 42 IVF embryos 42 sterile syringe 42 guideline concordant 42 placenta praevia 42 ENDOMETRIN R 42 placental stem cell 42 Lawyer Octuplets mom 42 Kidney transplantation 42 undergoing elective 42 DrThom 42 lipo suction 42 clomifene 42 abort fetus 42 Dr Armellin 42 epidural analgesia 42 causes uterine contractions 42 Mohammed Taranissi 42 intrauterine contraception 42 nasal saline 42 Nasdaq CPTS developer 42 perio 42 spayed vaccinated 42 Shahana Hashmi 42 Donnez 42 singleton pregnancies 42 maternal neonatal 42 cervical dilation 42 obstetric gynecology 42 fetal tissue 42 Gillian Lockwood 42 NEW OPTION 42 Corneal transplants 42 fetal nucleic acids 42 Post partum depression 42 nebulisers 42 Norman Fost 42 undergo breast augmentation 42 allogenic 42 aortic tissue 42 transfer SCNT 42 autologous transfusion 42 gamete donors 42 breastfeeds Sierra Leone 42 deriving stem cells 42 Embryology Authority HFEA 42 contraceptive implants 42 minimally invasive laparoscopic surgery 42 organ transplantations 42 exacerbate pituitary tumor 42 cardiology pulmonology 42 Janani Suraksha Yojana 42 bronchoscopes 42 Dr. Hovanesian 42 ovulation inducing 42 hormone hCG 42 unsterile 42 pectoral implants 42 Sumatra tiger cub 42 perinatal asphyxia 42 recurrent miscarriage 42 breastpump 42 CHDs 42 enucleated 42 pelvic reconstructive surgery 42 coumadin 42 interventional catheterization 42 hepatectomy 42 Bonati Procedures 42 HLA identical 42 gastrostomy 42 Pernicious anemia 42 administered intramuscularly 42 mutated K ras 42 estrus synchronization 42 anesthesia neuroanatomy obstetrics 42 AIUM 42 tenderly kiss 42 immune suppressant 42 conjoined Egyptian 42 ultrasound 42 embryos implanted 42 endoscopy suites 42 Sono Bello 42 endometritis 42 autologous cells 42 implants sterilized 42 octo mom 42 Kidney transplant 42 coronary CTA 42 infertility treatments 42 Flexi Scope 42 thyroid hormone replacement 42 decortication 42 Heavy menstrual bleeding 42 sterilisers 42 pediatric endocrinology urology orthopedics 42 posterior vaginal 42 Hormonal contraceptives 42 scarless 42 menstrual disorders 42 test FOBT 42 immunosuppressive medications 42 VoLumen 42 caesarians 42 coblation 42 AVImark ® 42 Caesarean Section 42 cardiac cath 42 urological gynecological 42 nasopharyngeal swab 42 Muraskas 42 de worming vaccinations 42 vaccinations worming 42 elective Caesareans 42 sperm fertilizes