M ANAGEMENT OF P OSTTERM P REGNANCY Leslie Ablard, MD OB/GYN Mowery Women’s Clinic Salina, KS 1

P OSTTERM = 42 WEEKS 2

D EFINITION : ACOG B ULLETIN 55, S EPT 2004 Postterm pregnancy refers to pregnancies that extend beyond 42 weeks gestation (294 days, or estimated date of deliver (EDD) +14 days) Accurate pregnancy dating is critical to the diagnosis The term “postdates” is poorly defined and should be avoided Although some cases are a result of the inability to accurate define the EDD, many cases result from a true prolongation of gestation Reported frequency of postterm pregnancy is 7% 3

E TIOLOGIC FACTORS Most frequent cause of prolonged gestation A. Placental Sulfatase deficiency B. Error in Dating C. Fetal Anencephaly Other Associations Male Sex Genetic Predisposition Primiparity h/o prior postterm pregnancy When postterm pregnancy truly exists, the most common cause is Unknown 4

A SSESSMENT OF GESTATIONAL AGE Accurate dating is important for minimizing the false diagnosis of postterm pregnancy MOST RELIABLY AND ACCURATELY DETERMINED EARLY IN PREGNANCY Questions at new ob visit When was the first date of your last period? Do you have regular cycles? Approx how many days between cycles? Are you sure about the given date? Where you on any birth control when you got pregnant? When did you first find out you were pregnant? 5

A CCURACY OF LMP There are many inaccuracies in even the “surest” of LMPs Recall Delayed Ovulation Irregular cycles Predicting delivery date by ultrasound and last menstrual period in early gestation. Obstet Gynecol Feb;97(2): Obstet Gynecol. The last menstrual period (LMP) was considered certain in 13,541 When ultrasound was used instead of certain LMP, the number of postterm pregnancies decreased from 10.3% to 2.7% (P <.001). 6

A CCURACY OF LMP Comparison of pregnancy dating by last menstrual period, ultrasound scanning, and their combination. Am J Obstet Gynecol Dec;187(6): Am J Obstet Gynecol women with sure LMP LMP reports prolonged gestation 2.8 days longer on average than ultrasound scanning, yielded substantially more postterm births (12.1% vs 3.4%), and predict delivery among term births less accurately 7

U LTRASOUND DATING ? When sure LMP and US vary greater than 8% Approx 7 days up to 20 weeks 14 days between weeks 21 days beyond 30 weeks 8

R ISKS TO THE FETUS Risk of perinatal mortality (stillbirth and early neonatal deaths) TWICE that of term. 4-7 deaths vs 2-3 deaths per 1,000 deliveries Increases SIX fold and higher at 43 weeks Uteroplacental insufficiency Meconium aspiration Intrauterine infection Postterm pregnancy is an independent risk factor for low umbilical artery pH at delivery and low 5 min APGAR scors Higher incidence of fetal macrosomia, although no evidence supports inducing labor as a preventative measure in such cases Prolonged labor, CPD, Shoulder Dystocia 9

R ISKS TO THE FETUS Approx 20% of postterm fetuses have dysmaturity syndrome Infants with characteristics resembling chronic IUGR from uteroplacental insufficiency Oligo, meconium aspiration, hypogycemia, seizures, respiratory insufficency, non-reassuring fetal testing Long term sequelae not clear One large prospective follow up study of children 1-2 yrs, general intelligence, physical milestones, and frequency of intercurrent illnesses were not significantly different between normal infants born at term and those born postterm Fetuses born postterm are at increased risk of death within the first year- most have no known cause 10

R ISKS TO THE PREGNANT WOMAN Increased labor dystocia- 9-12% vs 2-7% Increased risk in severe perineal injury related to macrosomia- 3.3% vs 2.6% Doubled rate of c-section----endometritis, hemorrhage, thromboembolic events ANXIETY 11

A RE THERE INTERVENTIONS THAT DECREASE POSTTERM PREGNANCY ? Accurate dating by early sono---not current standard of prenatal care in the US Membrane sweeping studies are conflicting 12

W HEN SHOULD ANTENATAL TESTING BEGIN ? No studies to state when the best time to start, frequency, or type of testing to use (no one with include an unmonitored control group) No data that testing adversely affects patients experiencing postterm pregnancy So, DO IT 13

P ERINATAL M ORTALITY Figure 1. (A) The rates of stillbirth (-▪-) and infant mortality (-) for each week of gestation from 28 to 43+ weeks expressed per 1000 live births. (B) The rates of stillbirth (dark gray) and infant mortality (light gray) in the same population of 171,527 singleton births expressed as a function of 1000 ongoing (undelivered) pregnancies. 14

W HAT FORM OF T ESTING ? Options include: NST, BPP, modified BPP (NST with AFI), Contraction Stress Test No single method superior Evaluation of AFI important Definition of oligo in the postterm not been established No vertical pocked more than 2-3 cm AFI less than 5 My choice- starting at 41 weeks- twice weekly monitoring including NST with modified BPP (NST + AFI) 15

I NDUCE OR WAIT Management of “low-risk” postterm pregnancy is controversial Factors to include- gestational age, results of antenatal testing, cervix, maternal preference Many studies exclude those with favorable cervices 16

U NFAVORABLE CERVIX Small advantage using cervical ripening agents Several large multicenter randomized studies of management after 40 week report favorable outcomes with routine inductions starting at 41 weeks Largest study found that routine induction at 41 weeks, found elective induction resulted in lower c-section rates primarily related to fewer c/s for non-reassuirng fetal heart rate tracings Patient satisfaction was also higher Meta-analysis of 19 trials found that routine induction after 41 weeks was associated with a lower rate of perinatal mortality and no increase in c/s rate and no effect on operative vag delivery, use of analgesia, or FHRA 17

I NDUCE AT 41 WEEKS ? Large amounts of evidence suggest that routine induction at 41 weeks gestation has fetal benefit without incurring the additional maternal risks of a higher rate of c-section. This conclusion has not been universally accepted Smaller studies report mixed results Two studies reported an increase in c/s rate among certain subgroups of patients – “high risk” 18

P ROSTAGLANDINS FOR INDUCTION Valuable tool Several placebo controlled trails have reported significant changes in Bishop scores, duration of labor, lower maximum doses of oxytocin, and reduced incidence of c/s. No standardized doses have been established Higher doses (especially PGE1) have been associated with tachysystole and hyperstimulation resulting in non-reassuring fetal status Lower doses are preferable with PG is used and FHR monitoring should be done routinely before and after placement 19

VBAC Do not use prostaglandins Foley bulb + pitocin Limited evidence on the efficacy or safety of VBAC after 42 weeks- no firm recommendations can be made 20

I NDUCTION OF LABOR 41 weeks? Consistently shown to have no increased morbidity/mortality even with nulliparous patients and unfavorable cervices 39 weeks? Multiparous patients appear to have no increase risk of c/s, morbidity, mortality Do have increased use of resources Conflicting data on nulliparous Recent study found no increase risk of c/s with unfavorable cervix after eliminating medical inductions (preeclampsia, diabetes, etc) Elective Induction Compared With Expectant Management in Nulliparous Women With an Unfavorable Cervix Elective Induction Compared With Expectant Management in Nulliparous Women With an Unfavorable Cervix Obstetrics & Gynecology. 117(3): , March May be a baseline risk for c/s un-related to gestational age or cervix 21

2447 women underwent c/s from 30 hospitals in LA and Iowa 25% c/s performed for “failure to progress” at 3 cm or less 40% of “prolonged 2 nd stage” did not meet ACOG criteria (45% nulliparous) 22

I NDICATIONS FOR C / S -32,443 patients undergoing c/s Obstet &Gynecol

F RIEDMAN CURVE 24

Z HANG ’ S NEW LABOR CURVE - SEPT ,838 women in non-augmented, active labor Multiparous do not enter active labor until 5 cm Nulliparous do not ener active labor until 6 cm Labor progresses more slowly than previously described 25

G IVE ‘ EM A CHANCE !! Friedman was wrong ( or wrong for today) Labor curve of modern times is slower with the active phase in primips not occurring until 6cm dilated! Many c-sections performed when not even in active labor Don’t be afraid of serial inductions Use all your armamentarium- prostaglandins, foley bulb, pitocin, AROM, FSE, IUPC, operative delivery 26

SUMMARY Postterm pregnancy may in itself be “high risk” Establish a EDD early and as precisely as possible- early sono? Consider antenatal testing at 41 weeks vs induction An unfavorable cervix may not be as much of a risk factor for c-section as underlying issues- macrosomia, fetal intolerance to labor, etc. Where is the nadir for fetal well-being and maternal outcomes? 39 weeks? 41 weeks? Patience is important for today’s labor curve 27

P OSTTERM P REGNANCY IS LIKE P OPCORN 28

T HANK YOU 29