pregnancy dating

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Dr.VeerendraKumar C.M. MD.,DNB. Associate professor Dept of OBG VIMS, Bellary Pregnancy dating veerendrakumarcm@gmail.com

The ‘due date’ : 

The ‘due date’ Social and medical significance Time frame around which many activities are planned

Accurately assess the gestational age : 

Accurately assess the gestational age To carry out specific prenatal tests To gauge fetal growth To take critical decision for specific obstetric complications

Lengths of pregnancy : 

Lengths of pregnancy Elephant- 640 days Dogs- 63 days Cat- 65 days Camel- 406 days Monkey- 164 days Mouse- 21 days Sheep- 150 days Cow- 280 days Human- 266 days

do we mature early? : 

do we mature early? Does gestation vary by ethnic group? A London-based study of over 122 000 pregnancies with spontaneous onset of labour Roshni R Patel1,2, Philip Steer3, Pat Doyle1, Mark P Little4 and Paul Elliott4 IJE vol.33 no.1 107-113 © International Epidemiological Association 2004; all rights reserved.

Metabolic nirvana …. : 

Metabolic nirvana …. The median gestational age at delivery was 39 weeks in Blacks and Asians and 40 weeks in white Europeans. Meconium stained amniotic fluid, which is a sign of fetal maturity, was statistically significantly more frequent in preterm Black and Asian infants and term Black infants compared with white European infants.

The age… : 

The age… 1.Menstrual age 2.Gestational age 3.Embryological age 2 1 3 2

Basic methods : 

Basic methods Menstrual history Clinical examination Ultrasound examination

Menstrual history : 

Menstrual history Indirect measure of conception of roughly 280 days Reliability depends and influenced by - recall of memory - presence of light bleeding - regularity of cycles - OCP, breast feeding etcNichols C. Dating pregnancy. J Nurse Midwifery. 1987;32:195-204.

Menstrual age : 

Menstrual age Overestimates the gestational age Wilcox M et al BMJ 1993;307(6904):588-91 10-45% do not provide correct information 18% with certain dates have significant difference with USG ageGeirsson et al, Br J Obstet Gynaecol. Jan 1991;98(1):108-9.

Naegeles’ rule does not correlate with actual conception date…. : 

Naegeles’ rule does not correlate with actual conception date…. Baird et al498 normal cycles luteal phase 7-19 days 10% ovulate on D14 Wicox et alonly 30% of normal cycle women are fertile between 10-17 days

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Reliable information on 1st day of LMP not equivalent with reliable information about the start of pregnancy

Still LMP is relied upon… : 

Still LMP is relied upon… Ovulation is not an easily observed event > 50% pregnancy are unintended LMP recall is error prone Indian Husbands more aware of their wives’ LMP! Most women may round off the dates or tell preferred dates May lead to misclassification as post term pregnancy

Naegeles revisited : 

Naegeles revisited 19th century Frederiech Naegele original article in German textbook Naegele himself credits Harmann Boerhaave with Inventing the formula for EDD. Its unclear whether 1st day of LMP or last day of LMP to be considered for EDD.

Other methods : 

Other methods Prem’s rule –based on BBT7days subtracted from 1st day of thermal shift and 9 months added M G Hiremath (KIMS Hubli)pt is ignorant about English calendardoctor is ignorant about Lunar calendar!

Time to discard naegeles? : 

Time to discard naegeles? Error prone EDD not acceptable in modern timesKatz VL et al Why we should eliminate the due date: A truth in jest. Obstet Gynecol. 2001;98:1127-1129 Gardosi J. Dating of pregnancy: Time to forget the last menstrual period. Ultrasound Obstet Gynecol. 1997;9:367-368 Savitz DA. Comparison of pregnancy dating by last menstrual period, ultrasound scanning and their combination. Am J Obstet Gynecol. 2002;187:1660-1666

That too when we know the embryo like this : 

That too when we know the embryo like this

Methods of determining the gestational age : 

Methods of determining the gestational age Parameter variability 2SDIVF 1 day Ovulation 3 daysIUI 3 daysSingle I/C 4 days 1st trimester examn 2 weeks2nd trimester examn 4 weeks3rd trimester examn 6 weeks Callen PW. Ultrasonography in obstetrics and gynecology. 5th ed. Saunders Elsevier; 2008;p. 3-25.

Methods of determining the gestational age : 

Methods of determining the gestational age Parameter Variability 2SD1st trimester USG –CRL ± 8% of the estimate 2nd trimester USG –HC,FL ± 8% of the estimate 3rd trimester USG – HC,FL ± 8% of the estimate Callen PW. Ultrasonography in obstetrics and gynecology. 5th ed. Saunders Elsevier; 2008;p. 3-25.

Ultrasound dating : 

Ultrasound dating RADIUS trial 1993 - 15,000 low risk women no clinical benefit to justify routine ultrasound in the absence of medical indications ACOG 2008 states that obstetricians are under no obligation to perform routine ultrasounds in low-risk women; however, it is reasonable to honor a patient's request for one.!! Ultrasonography in pregnancy. Obstet Gynecol. 2008;112:951-962.

Obstetric ultrasound turned intoUltrasonic obstetrics : 

Obstetric ultrasound turned intoUltrasonic obstetrics Sono obstetrician

RADIOLOGIST CAN SURVIVE WITHOUT SCAN : 

RADIOLOGIST CAN SURVIVE WITHOUT SCAN BUT NOT THE OBSTETRICIAN

All said … : 

All said … Ultrasound examination of the fetus provides the most precise assessment of gestational age, especially in the first trimester.Callen USG in Obst and Gynecol 2008 ACOG PRACTICE BULLETIN 2008

9 RCT, > 34,000 women : 

9 RCT, > 34,000 women Routine USG More accurate estimation of EDDearlier detection of twin pregnancies Neilson JP , Cochrane Database – Syst Review 2000 improved clinical management of parturient women

USG technology evolved.. : 

USG technology evolved.. The margin of error is consistently ±8% by esteemed researchersHadlock FP, Radiology. 1992;182:501-505 Doubilet ,J Ultrasound Med.1993;12:647-653 Taipale P, Obstet Gynecol. 2001;97:189-94

The classical understanding… : 

The classical understanding… 1st trimester ± 1 week2nd trimester ± 2 weeks 3rd trimester ± 3 weeks

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±8 % variance (Hadlock) of the estimated gestational age not in weeks but convert into days!i.e…8weeks = 56 days » 8% = 5 days24 weeks =146 days » 8%=12 days36weeks = 252 days » 8% = 20 days

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an ultrasound performed before 24 weeks' gestation establishes a more accurate EDD than relying solely on the LMP.Hadlock et al, Mongelli et al

Despite RADIUS…. : 

Despite RADIUS…. Significant reduction in post term induction when gestational age is established by USG 1st trimester dating 70% reduction rate in post term induction Mongelli M et al Estimating the date of confinement. Am J Obstet Gynecol. 1996;174:278-281

Despite RADIUS…. : 

Despite RADIUS…. In study of 17,000 women With reliable LMP dating post term delivery rate reduced from 10.3% to 2.7% Taipale P, Hiilesmaa V. Predicting delivery date by ultrasound and last menstrual period in early gestation. Obstet Gynecol. 2001;97:189-194.

SCAN IS A WONDERFUL INSTRUMENT IN THE RIGHT HANDS : 

SCAN IS A WONDERFUL INSTRUMENT IN THE RIGHT HANDS

Usg in First trimester : 

Usg in First trimester Gestational Sac (GS)use till embryo appearsMSDadd 30 to GS size in mm to get age in days CRL excellent correlation between GA and CRL till 12 weeks

CRL : 

CRL

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Sonoembryology

2nd trimester USG : 

2nd trimester USG Linear correlation with BPD, HCracial difference with FL, not with HCGA (DAYS) = 39.1 + 2.1 (BPD)in mm

3rd trimester : 

3rd trimester GA measurement less accurate than 2nd trimester Distal femoral epiphysis 32-33 weekssize linearly increases with GA7mm epiphysis at least 37 weeks Proximal tibial epiphysis GA at least 35 weeks

Man or the machine? Or.. Middle path : 

Man or the machine? Or.. Middle path

Dating discrepancy : 

Dating discrepancy Problem arises in (busy) clinical practice when significant difference exist between due date calculated by LMP and USGespecially when earlier scan is not done and patient presents late in pregnancy.

ultrasound biometryapproximation of assumption : 

ultrasound biometryapproximation of assumption In early pregnancy all fetuses of same age are of same size !Variation increases with increase in gestational age In late pregnancydifferent fetuses of same age are of different sizes

Reassigning the due date : 

Reassigning the due date ACOG recommends reassigning the date when difference exist between LMP & USG date. >7days difference up to 12 weeks > 10 days difference 12-20 weeks What about after 20 weeks?

Rule of 8 : 

Rule of 8 Hadlock regression analysisUSG gestational age estimation is consistently accurate with 8% margin of error irrespective of the GA.This SD is to be converted into days’ gestationHadlock F. Sonographic estimation of fetal age and weight. Radiol Clin North Am. 1990;28:39-50.

The problem.. : 

The problem.. LMP 13/01/03 EDD 20/10/03USG done on 1/7/03 gest age of 21 weeks 1day EDD 10/11/03 Difference is 20 days !which one to believe?

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Convert gestational age into days21wks 1day = 148 days 8% of Margin of error (MOE) = 148 x 0.08 = 11.84 = 12 days If difference is more than MOE use USG EDD If MOE is more than difference use LMP EDD MOE is less than the difference final EDD is 10/11/03

The baby was born on 2/11/2003 : 

The baby was born on 2/11/2003

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Use always earliest USG report Subsequent USGs can be used to rule out developmental abnormalities. Uniformity among obstetric providers without divergent opinion in arriving at Final EDD Busy tertiary care hospital consistency is crucial Allows residents to learn critically learn & examine the dating criteria Evidence based management with confidence

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Thank you