QuestionHello. I am considered high risk for this, my second past first term pregnancy, because my daughter was IUGR at term, 5.1 lbs. This was not diagnosed untill she was born, and we do not know the cause. With this pregnancy, I'm at 28 weeks. At 19 weeks, my cervix was 4.7 cm. At 24 weeks, it was 2.8. My Dr asked me to take it easy, but said that bedrest doesn't help stop preterm labour. I have had 2 sets of contractions that I went to the hospital for since 24 weeks. At 26 weeks, I was "holding steady" at 2.8cm, despite the contractions. I now just found out that I have an amniotic band that's between the fetus and my cervix, with the fetus' head down (I felt the baby "drop" before I found out that my cervix was shortening). SHould I be concerned about ABS or preterm labour, should I be on bedrest?
AnswerDear Danielle,
To explain the cause of ABS, there are two main theories. The amniotic band theory is that ABS occurs due to a partial rupture of the amniotic sac. This rupture involves only the amnion; the chorion remains intact. Fibrous bands of the ruptured amnion float in the amniotic fluid and can encircle and trap some part of the fetus. Later, as the fetus grows but the bands do not, the bands become constricting. This constriction reduces blood circulation, hence causes congenital abnormalities. The vascular disruption theory: Because the constricting mechanism of the amniotic band theory does not explain the high incidence of cleft palate and other forms of cleft defects occurring together with ABS, this co-occurrence suggests an "intrinsic" defect of the blood circulation.
Amniotic band syndrome is often difficult to detect before birth as the individual strands are small and hard to see on ultrasound. Misdiagnosis is also common so if there are any signs of amniotic bands further detailed ultrasound tests should be done to assess the severity. Unfortunately, until birth there usually is no way to know for certain if ABS has had any effect on the baby. Amniotic band syndrome is considered an accidental event and it does not appear to be genetic or hereditary, so the likelihood of it occurring in another pregnancy is remote. The cause of amnion tearing is unknown and as such there are no known preventative measures.
As far as pre-term labor risks related to a weakened or incompetent cervix, an incompetent cervix is the result of an anatomical abnormality. Normally, the cervix remains closed throughout pregnancy until labor begins. An incompetent cervix gradually opens due to the pressure from the developing fetus after about the 13th week of pregnancy. The cervix begins to thin out and widen without any contractions or labor. The membranes surrounding the fetus bulge down into the opening of the cervix until they break, resulting in 2nd trimester miscarriage, preterm premature rupture of the membranes (PPROM) when your water breaks before you're full-term and before you're in labor, or preterm delivery (before 37 weeks). It particularly increases your risk for early preterm delivery, which means giving birth before 32 weeks.
In the past, women weren't usually diagnosed with incompetent cervix until after she had experienced many very early deliveries or 2nd trimester pregnancy losses from no other apparent cause. Now, because of the ultrasound technology available, doctors will often discover this condition with a trans-vaginal ultrasound between 16-20 weeks (depending upon your OB history). A trans-vaginal scan is the best way to measure your cervix because it can be seen much more clearly this way. The cervix looks like a tube on the scan, approximately 3-5 cms in length, with one end at the top of the vagina (the external os) and the other end inside the womb (the internal os). It is the internal os that can begin to open first and this will look like a V shape on the scan. As the os opens further it becomes U shaped. This is called funneling. If the closed part of the cervix measures less than 2.5 cms, it is considered to be an incompetent cervix and a cerclage (see below) is often placed to keep the cervix from opening too early.
You're more likely to have this condition if:
-You've had a 2nd trimester miscarriage with no known cause or an early spontaneous preterm delivery in a previous pregnancy that wasn't caused by preterm labor or a placental abruption. It's even more likely if you've had more than one late miscarriage or early spontaneous preterm birth.
-You've had a procedure such as a cone biopsy or LEEP done on your cervix.
-Your mother took the drug DES while she was pregnant with you. (Caregivers used to prescribe this drug to prevent miscarriage, but stopped in the early 1970s when studies showed that it was both ineffective and caused reproductive tract abnormalities in developing babies.)
-Your cervix was injured during a previous birth or dilation and curettage (D&C), or you've had several pregnancies terminated.
-You have an unusually short cervix by nature. (There is nothing to contradict that this could be an inherited physical feature - just like any other feature like hair color or skin tone. This would tend to make sense, especially if it followed along maternal family lines.)
When ultrasound shows you have an abnormally short cervix and you're less than 24 weeks pregnant, your doctor may recommend a cerclage, a procedure in which he/she stitches a band of strong thread around your cervix to reinforce it and help hold it closed. However, there's a lot of controversy about whether cerclage should be used in this situation - especially beyond 16 weeks. Women who seem to benefit most from cerclage include those who've had three or more unexplained 2nd trimester losses or preterm births or who have a known incompetent cervix. Women in this group are likely to get a cerclage at 13 to 16 weeks, before the cervix starts to change. A cerclage done then appears less risky than one done later in pregnancy, after the cervix has started to change.
If cerclage cannot be performed, or the risk of losing the pregnancy is greater with cerclage than the potential benefit, many doctors will prescribe complete bedrest. Although there's no solid evidence that staying in bed is effective, the theory is that keeping the weight of the uterus off of a weakened cervix might aid in lengthening the term of the pregnancy until the baby is viable. You'll probably be advised to abstain from sexual activity also if your cervix begins to shorten to 2.5 cm or less. Right now, you are holding just barely above that cut-off point of 2.5 cm.
Call your doctor right away if you have any of these symptoms:
- Change in amount or type of vaginal discharge, particularly a mucousy or watery discharge
- Vaginal spotting or bleeding
- Menstrual-like cramping
- Pelvic pressure or "heaviness"
I hope this information has helped you and answered your question. I wish you well.
Brenda
