Calculating Due Dates
What are some reasons for false positives in urine pregnancy tests?
-Blood or protein in urine -Hormone treatments -Menopause -Medications -Medical Conditions -Improper use/reading/storage
When would you NOT use implantation bleeding to calculate a due date?
-Implantation time varies -Not experienced by all women -Implantation bleeding may be delayed -There can be other reasons for bleeding
What are problems with using quickening as a way to determine an EDD?
-Subjective information (may be misinterpreted for gas, intestinal movements, wishful thinking) -May be felt earlier with twins -May be felt later is woman is obese
What are some reasons for false negatives in urine pregnancy tests?
-Taken too early or too late -Improper use or reading of test -Improper storage
When can the AVERAGE urine pregnancy test detect positive pregnancy?
1-2 weeks after missed period 3-4 weeks after conception 5-6 weeks gestation
Give a limitation of Naegele's Rule or Gestational Wheel
1. Can't be used if LMP unknown 2. Can't be used for women with irregular periods 3. Can't be used for breastfeeding mothers who never had a period before conceiving 4. Can't be used for women who conceive before a regular period restarts after miscarriage, abortion, or stopping birth control
Give a reason that calculating a correct due date is important
1. To provide good midwifery care 2. It is in the best interest of the mom and baby 3. To monitor fetal growth and identify problems 4. To identify true prematurity or postmaturity.
When can fetal breathing movements be seen on US?
10-11 weeks
How many weeks gestation is a woman when her uterus is palpable at the symphysis pubis?
10-12 weeks
When can FHR be detected by doppler?
10-12 weeks
When do SENSITIVE urine pregnancy tests detect pregnancy?
10-14 days after conception 3-4 weeks gestation
How many weeks in the first trimester?
12 weeks (1-12)
How many weeks in the 3rd trimester?
13 weeks (28-40)
When can the biparietal diameter (BPD) be used to determine GA?
13 weeks and up
When does ovulation occur for ALL women, regardless of cycle length?
14 days before the start of the next period
How many weeks in the 2nd trimester?
15 weeks (13-27)
How many weeks is a woman when her uterus is half-way between symphysis pubis and umbilicus?
16 weeks
When can FHR be detected by a fetoscope?
16 weeks (for sure by 19-20 weeks)
When can quickening be felt in a multigravida?
16-18 weeks
When can quickening be felt in a primigravida?
18-20 weeks
How many weeks is a woman if her uterus is at the umbilicus?
20-22 weeks
When is the BPD most accurate?
20-30 weeks
After how many weeks does the FH correlate with the GA, generally?
22 weeks
How do you calculate a due date based on implantation bleeding?
266 days - 6 to 12 days = EDD
How long is gestation duration?
266 days/38 weeks
How many weeks is a woman if her uterus is half way between the umbilicus and xyphoid process?
28 weeks
How long is a normal pregnancy duration?
280 days/40 weeks/9 months
How many weeks is a woman when her uterus is 1 finger below the xyphoid process?
36 weeks
When can the gestational sac be seen by TRANSVAGINAL US?
4-5 weeks
How many weeks is a woman if her uterus is 2-3 fingers below the xyphoid process?
40 weeks
When can the gestational sac be seen by ABDOMINAL US?
5-6 weeks
When is the best time to measure crown-crump length (CRL) to determine GA?
6-12 weeks
When is the best time to use US to date a pregnancy if unsure of LMP?
6-12 weeks
When can the FHR be seen on US?
6-7 weeks
When can uterine size be palpated internally?
7 weeks
On what is Naegele's Rule based?
A normal 28-day cycle, assuming ovulation occurs 14 days after LMP
When can hCG levels be detected?
After implantation occurs
Is the CRL or BPD more accurate in determining GA/EDD?
CRL
How do you calculate a due date based on known date of conception?
Date of conception + 266 days
What is the Naegele's rule variation using known conception date?
Date of conception -3 months -7 days = EDD (for a 28 day cycle)
What is the method for calculating a due date based on known ovulation?
Date of ovulation + 266 days = EDD
EDB
Estimated Date of Birth
EDC
Estimated Date of Confinement
EDD
Estimated Date of Delivery
How can hCG blood tests predict a due date?
In early pregnancy, repeating a test 1 week after the first one can predict a GA or EDD +/- 3-5 days. (based on rise in hCG levels)
Which monthst have 31 days?
January, March, May, July, August, October, December
What is the calculation for Naegele's Rule?
LMP -3 months, +7 days
What is LNMP
Last Normal Menstrual Period
What are some factors that can affect the uterine size and FH?
Malnutrition Ethnicity Height/build Uterine abnormalities Uterine position/presentation Multiple pregnancy (twins) Full bladder AFV Placental location Midwife subjectivity
What is one of the most reliable and accurate methods of dating a pregnancy, if the woman has kept accurate records?
Ovulation history
What is the difference between pregnancy duration and gestational duration?
Pregnancy duration= LMP--> birth Gestation duration= Conception--> birth (fetal age)
Which months have 30 days?
September, April, June, November
What should you tell your patient about calculated due dates?
That it is only an estimation and they may deliver +/- 2 weeks from the EDD
What is implantation bleeding? When does it occur?
Trauma to the uterine lining when implantation occurs that can cause bleeding or spotting for a few days. It occurs 3-4 weeks after LMP, or 6-12 days after conception (Can be mistaken for LMP)
When should someone repeat a pregnancy test to confirm results?
Within a week from the first test
What hormone to pregnancy tests detect?
hCG
