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Ultrasound due date and c-section

Hi, I am 38 and pregnant w/my 2nd child. 1st child was delivered via c-section at 41 wks exactly. Attempted vaginal delivery, but after 24 +hours in labor (took me over 24 hrs to fully dilate and efface) and almost 3 hrs of pushing (daughter never made it past +1 station), c-section was performed. Diagnosis was arrest of descent and was told I have a narrow pubic arch. Despite difficult delivery, daughter experienced no distress the entire time (no decelerations, etc.). Apgars were 9 and 9-she is perfectly normal. Weighed 7 lbs 14 oz at delivery. My pregnancy (delivered at age 35) was completely normal- no high blood pressure, gestational diabetes,swelling, preterm labor (I was overdue but not induced; labor occurred naturally). I have no hx of any health problems, nor does my husband, and both families have excellent health.With this pregnancy I had my 1st u/s at 8 wks (on 2/26/09) to confirm the pregnancy.1st day of my LMP was 1/2/09- this is definitive as I was charting & using an ovulation monitor. Ovulated on day 11-12. My due date prior to the u/s was determined to be 10/9/09. This date was pushed earlier a full week to 10/2/09 b/c the CRL was 19.7 mm. Am having a planned c-section w/ this pregnancy.Concerned about lung maturity at the time of delivery. If the c-section date is scheduled @ 38 wks using the u/s due date (which would really be 37 wks based on first day of LMP), is there a risk of the lungs not being fully matured? I'm even concerned with 39 wks (which would be 38 wks based on first day of LMP). From what I understand, size doesn't mean that the lungs have properly matured, and u/s closer to time of delivery isn't a definitive indicator of lung maturity.Worried sick that baby will be delivered too early w/out full lung maturity.U/S 2 days prior to delivery w/1st child showed no excessive amniotic fluid. Please advise what week you would consider a safe delivery/lung maturity date when my due date has been moved 1 wk earlier due to u/s findings.
1 Responses
527625 tn?1229492858
You have asked a very insightful question that does not have an easy answer.  In general, the risk of "premature lungs" (inadequate production of lung surfactant) decreases weekly so that by 37 weeks, the vast majority of babies will have "mature" lungs (adequate surfactant production).  Even full term babies, however, have a very small risk of surfactant deficiency.

The gestational age obtained on early ultrasounds is considered to be very reliable.  Most neonatologists and perinatologist would consider induction of labor/elective cesarean section after 37 weeks of gestation depending upon the indication for delivery.  So overall, the actual risk of surfactant deficiency is extremely low, although it is never really quite zero even at 40 weeks.
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