Table 1 Summary of published studies using imaging technologies to assess membrane thickness

Frigo, et al

1996

Ex vivo

28 (13 primiparas, 15 multiparas) Mean GA 39 1/7 weeks.

Measurements with ultrasound and light microscopy 1 h postpartum. Samples from region of the internal os.

Membrane thickness correlation coefficient by ultrasound vs. histology, r = .96, p < 0.0001

Limited sample size, term deliveries only, in vitro study design, lack of precise location of membrane thickness measurement for consistency

Frigo, et al

1998

Ex vivo

32 (18 primiparas at 28–32 weeks with PPROM, 11 Cesarean sections, 7 vaginal deliveries, compared to 14 primiparas at 28–32 weeks with intact membranes delivered following induction for chromosomal abnormalities or fetal malformations)

Measurements of fetal membrane thickness with ultrasound and light microscopy 5 cm away from the umbilical cord within 1 h postpartum.

Membrane thickness in PPROM group was thinner, p < 0.0001. Correlation coefficient for ultrasonography versus histology was r = 0.92, p < 0.0001. No significant fluctuations in membrane thickness were observed between 28 and 32 weeks. No differences between vaginal delivery and Caesarean section, nor any significant regional differences. Leukocyte infiltration of the entire amniochorionic membrane was seen in patients with PROM with a significantly thicker intermediary zone, p < 0.0001.

Limited sample size, chromosomal abnormality or fetal malformation only in control group, in vitro study design, lack of precise location of membrane thickness measurement for consistency

Severi, et al

2008

In Vivo

158 singletons, transabdominal ultrasound at 18–25 weeks .

Measurement of fetal membrane thickness 3 cm from umbilical cord insertion site.

Women who delivered preterm had a greater membrane thickness than those who delivered at term, p < 0.0001. Significant inverse correlation between membrane thickness and gestational age at delivery.

Lack of precise location of membrane thickness measurement for consistency, transabdominal only, fetal membranes only measured once.

Basaran, et al

2014

In Vivo

190 singleton pregnancies

Measurements performed twice, 3 cm from umbilical cord insertion. The first time was between 18 and 22 weeks.

No difference in fetal membrane thickness in the second or third trimester between those who delivered term vs. preterm, p = 0.542 for second trimester, p = 0.448 for third trimester.

Population with low preterm birth rate (6.8%), lack of precise location of membrane thickness measurement for consistency, transabdominal only. 28 women lost to follow up for second measurement but included in analysis.