Antenatal care Flashcards
What is the time line of assessment during 1st trimester?
10-12 weeks: dating scan and AN blood
11-13weeks +6: 1st trimester combined test for down syndrome
Between booking visit and 16 weeks: early OGTT if needed
What is the time line of assessment during 2nd trimester?
- 16-19 weeks +6: 2nd trimester quadruple test for DS
- 18-22 weeks: anomaly scan
- 28-32 weeks: routine OGTT (should be done twice)
- 35-37 weeks: GBS screening
What are the tests during antenatal assessment?
- Confirmation of prengnacy
- Estimated date of delivery (EDD)
- Dating scan
How to confirm pregnancy during antenatal assessment?
Background: implantation occurs 7 days after ovulation and completes 14 days after ovulation. hCG is produced after implantation. hCG is detectable in serum 1 week after fertilization. hCG is detectable in urine 2 weeks after fertilization (4 weeks after LMP). Patient usually first notice the possibility of pregnancy after 1 missed period (4 weeks after LMP)
Urine pregnancy test: less sensitive than serum hCG detection. Test should be repeated in 1 week despite an initial negative test
Serum pregnancy test: most sensitive method for detecting hCG in early pregnancy. Positive within 1 week after presumed date of conception (post fertilization)
How to calculate estimated date of delivery?
Menstrual age = clinical assessment of gestational age or duration of pregnancy
Embyronic age: date development events from time of fertilization by embyrologist
EDD = 280 days from the onset of LMP (provided that ovulation occurs at day 14). Or 266 days from the day of ovulation and conception
Naegeles rule: EDD = 1st day of LMP + 7 days - 3months + add 1year
Limitation: assumption of woman having a regular 28 day cycle and is inaccurate due to variability in length of follicular phase. Variations in duration of time between fertilization and implantation
When is dating scan done in pregnancy?
What mode is it done in?
What are the indications?
USG assessment done in 1st trimester (10-12 weeks) because 1st trimester gestational age assessment is more accurate than 2nd trimester due to less biological variations (steady growth rate)
TVS is used for early 1st trimester for evaluation of gestational sac, yolk sac and developing embyro. TVS measures crown rump length (CRL) easier
TAS provides better visualization of pregnancy after uterus grows out of pelvis into mid and upper abd
Indications
* Menses are irregular
* LMP is unknown or uncertain
* Patients concieving while taking oral contraceptives
During a dating scan for pregnancy what should be noted?
What are the 2 main parameters used for dating a fetus?
- Gestational sac: visible at 4.5-5 weeks of gestation. Only used for dating in early pregnancy. Should not be used when crown rump length can be obtained or mean sac diameter >14mm (MSD grows 1mm per day). If the MSD >25mm, should see fetal pole.
Gestational age = MSD (mm) +30 (when MSD <14mm) - Crown rump length: longest straight line measurement of embyro measured from outer margin of cephalic pole to the rump. Standard biometric measurement of embyro in 1st trimester and most accurate during 7-10 weeks
Estimation of gestational age when CRL <84mm. Gestational age (days) = CRL (mm) + 42 (when CRL <25mm) - Cardiac activity: if fetal pole >7mm, should see the fetal heartbeat
- Detection of cardiac activity establishes gestational age of 5.5-6 weeks if the embyro is too small to measure adequately
What methods can be used to date gestation in 2nd trimester?
- Biparietal diameter: longest diameter between 2 parietal eminences and reflects brain growth. Measured on a plane of section that intersects both 3rd ventricle and thalami
Significance of biparietal diameter measurement - Dating in 2nd trimester
- Estimation of fetal weight
- Monitoring of fetal growth (relatively spared in asymmetric IUGR/ dolichocephaly/hydrocephaly/microcephaly)
Femur length: distance between ends of metaphysis and reflects the longitudinal growth
Significance
* Dating in 2nd trimester
* Estimation of fetal weight
* Monitoring of fetal growth (IUGR/ congenital dwarfism)
What is the PE that can be done to assess gestational age?
What are the antenatal blood tests done?
- CBC with MCV
- Rhesus group
- Rubella Ab
- HBsAg
- VDRL
- HIV Ab
- 1st and 2nd trimester down syndrome screening tests (1st trimester (11-13w +6): nuchal translucency, free B-hCG and PAPP-A, 2nd trimester (16-19 week +6): AFP + hCG +uE3 + inhibin A)
- OGTT (twice): between bookign visit and 16 weeks + between 28-32 weeks
- GBS screening (35-37 weeks)
What is the purpose of CBC in antenatal blood testing?
How to make prenatal dx?
MCV <82 +ve, partner will be tested. If both parents are +ve, both parents will be further tested by Hb electrophoresis.
If both parents are alpha or B thalassemia minor (trait), there is 1/4 risk for offspring to suffer from homozygous alpha or B thal and thus prenatal dx indicated
Prenatal dx accomplished by
* >18 weeks of gestation: serial USG exam to detect features such as cardiomegaly, placentomegaly, IUGR and hydropic changes
* <18 weeks of gestation. 1st trimester: CVS for DNA mutation analysis. 2nd trimester: amniocentesis for DNA mutation analysis
What is the purpose of Rhesus group in antenatal blood testing?
Patients who are Rh (D) negative will have red cell antibody screening (at 28 weeks)
Rh(D)-ve women with ongoing pregnancy with anti-D antibodies will be referred to prenatal dx clinic for FU of possible isoimmune hemolytic aneia of fetus: once alloimmunization occurs anti(D) immunoglobuilin is not effective for preventing hemolytic disease of newborn
Rh(D)-ve women without anti D antibodies will have anti-D antibody titre checked at 28 weeks.
Women who had not developed anti D antibodies by 28 weeks will recieve routine antenatal anti-D prophylaxis at 28 weeks
* 1 dose of anti-D (1500 IU prefilled syringe) given
* Given at 28 weeks (after blood taken for anti D antibody titre)
* No need to check anti-D antibody titre again until delivery after routine prophylaxis given at 28 weeks
Antenatal prophylaxis for potential sensitizing events: additional dose of anti D will be given to non sensitive Rh (D) -ve women with potential sensitizing events
Prophylaxis after delivery: if mother not sensitized after delivery and baby is Rh(D)+ve, she will be given anti-D prophylaxis (kleihauers test)
What is the purpose of rubella antibody in antenatal blood testing?
Not recommended to give rubella vaccination during pregnancy since it is a live attenuated virus vaccine
Advise contraception for 3 months after vaccination: even if vaccination occurs within 3 months to or during pregnancy the risk of congenital abnormality is very small.
What is the purpose of HBsAg in antenatal blood testing?
How to manage if mother is HBsAg positive?
Is there any counselling for breastfeeding?
Vertical transmission can occur in utero, at time of birth or after birth: usually occur at delivery from maternal blood or body fluid and transplacental transmission is very rare
Infection rate of infants born to HBsAg+ve mothers in 10-20% but as high as 90% if no HBIG and hep B vaccination at birth. Risk of transmission is even higher in mother who is HBeAg+ve or has a high HBV DNA viral load
Treatment:
* Antiviral therapy to mothers with high HBV viral loads: tenofovir (TDF) is safe in pregnancy and is used as 1st line agent
* Infants born to mothers who are HBsAg+ve should recieve both active and passive immunization (HBIG and HBV vaccine). Active immunization by HBV vaccination with protection. Passive immunization by HBIG (within 24 but not> 48 hours). Combined HBIG +HBV vaccination = 95% protection
* Results of immunization: 95% develop anti-HBs, 100% protection if anti-HBs becomes +ve
Counselling: breastfeeding does not increase risk of transmission
What is the purpose of VDRL in antenatal blood testing?
What are the maternal and fetal complications?
Treatment?
Counselling?
Vertical transmission can occur due to transplacental transmission to fetus after T.pallidum infects the placenta
Complicaitons of syphilis
Maternal = miscarriage/stillbirth/preterm delivery/prematurity
Fetal = IUGR/ congenital syphilis
* Early congenital syphilis = hepatomegaly/ placentomegaly/ anemia/ hydrops/ syphilitic rhinitis (snuffles)
* Late congenital syphilis. Hutchinson triad = hutchinson teeth +interstitial keratitis +sensorineural hearing loss. Facial features: saddle nose/frontal bossing/short maxilla. Oropharynx: mulberry molar/hard palate perforation. Skeletal: saber shins (anterior bowing of shin)/clutton joint (painless arthritis of knees)
Treatment: single dose penicillin G benzathine IMI. Penicillin is the standard and only appropriate and safe treatment for syphilis during pregnancy.
Counselling: explain syphilis is one type of STDs and refer to STD clinics. Vaginal delivery and breastfeeding not contraindicated
What is the purpose of HIV Ab in antenatal blood testing?
Mx?
When should C-section should be considered?
What is counselled for breastfeeding?
Requires patients consent before HIV screening. There is 15-40% chance of mother to baby transmission in infected women.
Positive result means individual has been infected. Negative results means individual is not infected but there is a window period of up to 3 months afer injection during which Ab is not detectable. Test should be repeated 3 months after possible exposure if there is high suspicion of infection
Mx: antepartam + intrapartum + post partum +infant prophylaxis
Intrapartum = zidovudine + lamivudine + nevirapine (all drugs started at onset of labor or 3 hours before elective C-section)
Postpartum = zidovudine +lamivudine (all given for 7 days before referral to HIV physician)
Antiretrovirsl treatment for newborn prescribed by paeds
Fetal scalp blood sampling, fetal scalp electrode insertion should be avoided
BCG vaccination should be withheld
C section should be considered: adequate ARV started 3 hours before C/S unless it is urgently indicated for obstretic indications.
Should not be offered to every patient with a positive test C/S in the following are unlikely to reduce transmission risk
* Labor is advanved
* Before adequate ARV is given
* Emergency C/S performed when patient has ruptured membranes for a long time
Avoidance of breastfeeding should be counselled
What is tested in the1st and 2nd trimester down syndrome screening tests?
When are they done?
What is the purpose of OGTT in antenatal blood testing?
When is it done?
When is GBS screening done for pregnancy?
All women recieve routine screening at 35-37 weeks before deciding whether intrapartum antibiotic prophylaxis is indicated in the current pregnancy. Prophylaxis aims to prevent early onset GBS disease in the newborn.
What are the types of thalassemia?
What is the degree of severity in alpha thal?
What chromosome codes for alpha globins?
What is the degree of severity in beta thal?
What chromosome codes for beta globins?
What is the 4 types of alpha thal and their clinical manifestation?
What is the 4 types of B thal and their management?
What is the 3 types of B thal and their clinical manifestation??
What is the PE for suspected thalassemia?
What are the biochemical tests for suspected thalassemia>
How can the iron profile be used to assess thalassemia?
How can Hb electrophoresis/chromotography and DNA mutation analysis be used for thalassemia?
What is the treatment for the differen types of alpha thal?
What is the treatment for the differen types of Beta thal?
What is the FU frequency and what Ix done for patients in thal major?
What is genetic counselling for alpha thal?
What is prenatal diagnostic strategy for alpha thal?
What is genetic counselling for beta thal?
What is prenatal diagnostic strategy for beta thal?
What is the prenatal diagnostic strategy for couples discordant for alpha and B carrier status?
Compound heterozygote of both alpha and B thal: condition is indistinguishable on routine haematological tests from the pure heterozygous state.
What is the rhesus system?
Under what setting does hemolytic disease of the fetus and newborn (HDFN) occur for Rh?
What are the potential sensitizing events that may require antenatal prophylaxis (anti D)?
- Antepartum hemorrhage
- Ectopic pregnancy at any gestation
- Miscarriage: spontaneous miscarriage >12 weeks not requiring interventions. Threatened miscarriage < 12 weeks. Threatened miscarriage >12 weeks –> consider 6 weekly injection if recurrent bleeding. If intermittent uterine bleeding after 20 weeks, estimation of fetomaternal hemorrhage by Kleihauers test should be carried out at 2 weekly interval
- Termination of pregnnacy: medical/surgical treatment for TOP at any gestation
- Fetal death
- Obstretics proceures: ECV, amniocentesis/chorionic villi sampling
- Transfusion related: inadvertent transfusion of Rh (D)+ve platelets to Rh(D) negative women
- Abd trauma
What is the facial and MSS features of down syndrome?
What are the CVS, respiratory, GI, urogenital and other AE manifestations of down syndrome?
When is down syndrome antenatal screening done?
What if there is positive results?
What is the morphology scan features (2nd trimester) of down syndrome?
