In the Name of GodObstetrics Study Guide 2 Mitra Ahmad Soltani 2008 Med-ed-online.org
References 1- All India Medical Pre PG. Fetal maturity &length of foetus. 2007. See: www.aippg.net/forum/viewtopic.php?t=33005 2-Brinholz J. Gestational age.American Journal of Roentgenography. 1984. 142 (4): 849 3- Cunningham G, Gant N, Leveno K, et al. Williams Obsterics. 22nd Ed . New York : Mc Graw Hill, 2005. 4- Durham J .Transition to Parenthood: How accurate is your due date. 2004 see: www.transitiontoparenthood.com/ttp/parented/pregnancy/duedate.htm and www.pregnancy.about.com/library/weekly/aa042197.htm 5- Friedman E. Obstetrical Decision Making. Harvard Medical School. 1981 6- Military Obstetrics and Gynecology. BrooksidePress. Estimating Gestational age. 2006 See: www.brooksidepress.org/.../Pregnancy /estimating_ gestational_age.htm 7-Mitchell P. A Comparison of Gestational Age Information Derived from the Birth Certificate, 1990 – 1998 . Alaska Vital Sign.2000. 8 (1):1-7 See: www.hss.state.ak.us/dph/bvs/PDFs/vitalsigns/avs_0801.pdf 8- Mittendorf R, Williams M, Berkey C, Cotter P. . The Length of Uncomplicated Human Gestation. Obstetrics & Gynecology.1990 . 75(6):929-932 Pictures and material on Breech and C/S are adapted from emedicine e-Journal with permission: 9-Fischer R. Breech Presentation.emedicine.2006 10- Sehdev H. Cesarean Delivery. emedicine. 2005
1- Nägele’s Rule • This was developed in the 1850’s by Dr. Nägele. To calculate this, one should add 7 days, and then subtract 3 months from LMP. • ((LMP + 7 days) - 3 months) = Expected Date of Delivery • Example: ((the LMP on 1st April + 7 days) - 3 months) = January 8 • This “rule” doesn’t take into account the fact that many women are uncertain of the date of their last menstrual period, not all women have 28 day cycles, and not all women ovulate on day 14 of their cycle.
2- Mittendorf’s Rule • To calculate “Mittendorf’s Rule”, one should add 15 days for first time Caucasian women, or add 10 days if non-white or this is not the first baby. Then subtract 3 months. • ((LMP + 15 days) - 3 months) = Expected Date of Delivery for first time pregnant Caucasian women • Example: (( LMP on 1st April + 15 days) - 3 months) = January 16
3-Ultrasound: • Measurement of a Crown-Rump Length during the first trimester (1-13 weeks) will give a gestational age that is usually accurate to within 3 days of the actual due date. • During the second trimester (14-28 weeks), measurement of the biparietal diameter will accurately predict the due date within 10-14 days in most cases. • In the third trimester, the accuracy of ultrasound in predicting the due date is less, with a plus or minus confidence range of as much as 3 weeks.
FL • Femur length measurements can have a correlation coefficient of 0.995 with gestational age in a group of healthy fetuses with known date of conception. • Nevertheless, it still cannot be used exclusively because it may be relatively short in the presence of growth retardation, or long when growth acceleration has occurred, introducing comparable errors in age estimate if the underlying growth pattern is not appreciated.
4- Heart Tone: • Fetal heartbeat can be heard through Doppler starting at 9-12 weeks and by stethoscope at 18-20 weeks. • This event, however, is less accurate because the mother is not permanently attached to a Doppler device so the first heart beat can not be clued definitely.
5- MacDonald's Rule • Fundal Height (the distance from the symphysis pubis joint to the fundus of uterus) can be a rough estimate of gestational age. • Typically, from week 24 to week 34, fundal height in centimetres correlates with weeks of gestation. For example, at 28 weeks, the fundus is probably about 28 cm.
If a tape measure is unavailable, some rough guidelines can be used: • At 12 weeks, the uterus is just barely palpable above the pubic bone, using only an abdominal hand. • At 16 weeks, the top of the uterus is 1/2 way between the pubic bone and the umbilicus.
• At 20-22 weeks, the top of the uterus is right at the umbilicus. • At full term, the top of the uterus is at the level of the ribs. (xyphoid process).
6-Quickening • Some believe the baby will come five months after quickening, the first time the mother feels the baby move. • This is hard to evaluate, as women can be more or less sensitive to these sensations, and may notice them at different times in their pregnancies. • First time mothers typically notice movement around 18-20 weeks. Mothers who have been pregnant before notice it as early as 16 weeks.
7-Length of fetus • a- Crown-Rump Length: CRL is measured in first half of pregnancy; that is, up to 20 weeks measure from the Vertex to Coccyx. The fetal length is more helpful in prematurity than in post maturity, because after term the confidence interval for estimation surpasses 3 weeks.
CHL- Hasse’s rule • b- Crown-Heel Length : • CHL in the first half of pregnancy is the number of lunar monthsx 4. The CHL of a 4 month fetus is 16cm : 4x4=16 cm • From the end of 20 weeks in the second half of pregnancy, CHL in cm is the result of multiplication of the number of lunar months at the time of the assessment by 5. The CHL of an 8-month fetus is 40 cm: 8x 5 =40 cm
Normally, at the end of the following weeks gestation: • Before 20-24wks, the height of the fundus from pubic symphysis to umbilicus multiplied by 2/7 equals duration of pregnancy in lunar months or x 8/7=duration of pregnancy in weeks. • After 20 weeks, the fetal length in inches is equal to half of the number of gestational age in weeks. For example at 28wk the the height of the fundus from pubic symphysis to umbilicus is 14 inches.
8-Estimation of fetal weight in grams: Johnson’s Formula • (applicable only in Vertex presentation): Fundal height (cm) above the pubic symphysis minus 12 if Vertex above Ischial Spine or minus 11 if below Ischial Spines- should be multiplied by 155. This will be fetal weight in grams. • e.g., 32(fundal height)-12(constant) x155( constant) => 20 x 155=3100gms
9-Changes in Weight Gain: • Normally there is a steady increase in weight of a pregnant woman until the last 2-3 weeks of pregnancy. The woman stops gaining weight at about term. It may remain stationary or may begin to fall which means that pregnancy is at least mature.
Weight gain • In normal pregnancy –the weight gain should not exceed 2 ½ kilograms in any one month or 0.9 kg in a week. The maximum permissible weight gain throughout the whole period of pregnancy is about 10 or 11 kg (about 24 lbs) although 12 ½ kg is allowed—1/3rd of this weight—increases in the first 20 weeks, and another 1/3rd in the next 10 weeks. The Remaining 1/3rd would be gained between 30 weeks to term.
10- The age from conception: • The date of conception from a basal body temperature chart or known time of intercourse is the best measures for gestational age determination. But, relatively few women can state the events.
LNMP known Unknown or uncertain Gathering other data: 1-Date of intercourse 2- Date of positive Pregnancy test 3-Signs of pregnancy 4-First heard FHR 5-Quickening 6-Rate of uterine growth Nagele Rule Matches clinical gestational age Accepted Doesn’t match with clinical gestational age Ultrasound US does not match clinical gestational age. Either wrong estimate of gestational age or IUGR
SROM • Membrane rupture without spontaneous uterine contractions happens in 8% of term pregnancies. • At Parkland Hospital labor is stimulated with oxytocin when ruptured membranes are diagnosed at term and labor does not spontaneously ensue.
Which is an unreliable sign for chorioamnionitis? A-T=>38 c B-maternal and fetal tachycardia C-fundal tenderness D-maternal leukocytosis Answer:d
Sample Chorioamnionitis Order • General: condition/position/diet=NPO • Lab: CBC diff, MP, WW, B/C X2, U/A , U/C,CXR,BUN/Cr • IV : 1000cc Ringer +10 units of oxytocin start at 2 drops /min, add 2 drops every 15 min if FHR and contractions are normal Amp ampicillin 2gr iv qid +gentamicinim 80mg stat then 60 mg TDS AMP clindamycin 900 mg iv TDS for allergic women to penicillin(continue antibiotics after delivery until the mother is a febrile OTHER: Control of vital sign hourly
Induction Indications • Membrane rupture without spontaneous onset of labor • Maternal hypertension • Nonreassuring fetal status • Postterm gestation • Elective induction for the convenience of mother or the practitioner is not recommended.
Induction contraindications • Classical incision or uterine surgery • Placenta previa • Appreciable macrosomia, hydrocephalus, Mal presentations • Non reassuring fetal status • CPD • Active genital herpes in mother
E2 gel (dinoprostone) • Dosage: Intracervical gel(Prepidil ):2.5 mL/0.5 mg Vaginal insert(cervidil) 10 mg • The insert provides slower release of medication
E2 administration • An observation period ranging from 30 minutes to 2 hours for uterine activity and FHR may be prudent. • Oxytocin induction should be delayed for 6 to 12 hours. • Cautions in patients with glucoma, severe hepatic or renal impairment, or asthma are needed.
E1 misoprostol(cytotec) • Oral , intravaginal but not intracervical • Possibly superior to E2 gel Dosage: • 25 mcg intravaginal dose • 100 mcg oral
Oxytocin contraindications • ab fetal presentations • marked uterine over distension • Six or more previous pregnancies • Previous uterine scar and a live fetus • CPD
Oxytocin regimens • Low dose: start with 0.5-1 mu/min (one drop) add 1 mu/min every 30-40 min up to 20 mu/min • Low dose: start with 1-2 mu/min (two drops) add 2 mu/min every 15 min up to 20 mu/min • High dose: start with 6 mu/min (12 drops) add 6 or3 or1 mu/min (according to the presence of recurring hyperstimulation)every 15-40 min up to 42 mu/min. • When hyperstimulation occurs the infusion rate is halved.
oxytocin • Mean half life 5 min, • 10-20 units (10000 to 20000 mu) mixed into 1000 mL of lactated Ringer solution which makes a 10-20 mu/mL.
Indication for forceps or vacuum delivery Maternal: • heart disease, • pulmonary compromise, • intrapartum infection, • exhaustion, • prolonged 2nd stage of labor: more than 3 hrs in NP(2 for MP)with and more than 2 hrs in NP (1 for MP) without epidural analgesia. Fetal: • Cord Prolapse • Abruptio • Non reassuring fetal heart rate
Classification of forceps or vacuum • Outlet: scalp is visible at the introitus without separating the labia • Low: leading point of fetal skull is at station=>+2cm and not on the pelvic floor • Mid forceps: station above +2cm but head is engaged • High: not included in the classification
Contraindication for vacuum delivery • Nonvertex presentations • Extreme prematurity • Fetal coagulopathies • known macrosomia • Above zero stations • Lack of experienced operator who would abandoned the procedure if it does not proceed easily or if the cup “pops off” more than three times.
Vacuum technique • The center of the cup should be over the sagittal suture and about 3 cm in front of the posterior fontanel. • The full circumference of the cup should be palpated both prior to as well as after the vacuum has been created and prior to traction. • The suction should be increased to a negative pressure of 0.8 kg/cm² . • Traction should be coordinated with maternal expulsive efforts.
Breech PresentationPictures and material are adapted from :Fischer R. Breech Presentation.emedicine.2006with permission
Incidence • Breech presentation occurs in 3-4% of all deliveries. • 25% of births prior to 28 weeks' gestation • 7% of births at 32 weeks' gestation • 1-3% of births at term
Predisposing factors • Fetus to AF ratio(prematurity, polyhydramnios) • Intrauterine space(uterine malformations or fibroids, placenta previa, multiple gestation) • and fetal abnormalities (eg, CNS malformations, neck masses, aneuploidy),
Types • Frank breech (50-70%) - Hips flexed, knees extended (pike position) • Complete breech (5-10%) - Hips flexed, knees flexed (cannonball position) • Footling or incomplete (10-30%) - One or both hips extended, foot presenting
Vaginal Delivery • Spontaneous breech delivery: No traction or manipulation of the infant is used. This occurs predominantly in very preterm deliveries. • Assisted breech delivery: This is the most common type of vaginal breech delivery. The infant is allowed to spontaneously deliver up to the umbilicus, and then maneuvers are initiated to assist in the delivery of the remainder of the body, arms, and head.
Total Breech Extraction • Total breech extraction: The fetal feet are grasped, and the entire fetus is extracted. • Total breech extraction should be used only for a noncephalic second twin. • Total breech extraction for the singleton breech is associated with a birth injury rate of 25% and a mortality rate of approximately 10%.
Footling breech presentation: A singleton gestation should not be pulled by the feet because this action may precipitate head entrapment in an incompletely dilated cervix or may precipitate nuchal arms. As long as the fetal heart rate is stable and no physical evidence of a prolapsed cord is evident, management may be expectant while awaiting full cervical dilation.
Assisted vaginal breech delivery1: Thick meconium passage is common as the breech is squeezed through the birth canal. This is usually not associated with meconium aspiration because the meconium passes out of the vagina and does not mix with the amniotic fluid.
Assisted vaginal breech delivery2: The Ritgen maneuver is applied to take pressure off the perineum during vaginal delivery. Episiotomies are often performed for assisted vaginal breech deliveries, even in multiparous women, to prevent soft tissue dystocia.