Table 1 Demographic characteristics of the study population. Continuous variables were compared between groups using Welch’s t-test and are summarized as medians (interquartile range). Categorical variables are shown as number (%) and were compared using a Fisher’s exact test

Age

25 (23–29.75)

27 (23–31)

0.302

Body Mass Index

26.2 (24.1–30.3)

28.3 (24–34)

0.462

Parity: 0

8/30 (26.7%)

3/68 (4.4%)

0.003

≥1

22/30 (73.3%)

65/68 (95.6%)

 African American

26/30 (86.7%)

56/68 (82.4%)

NS

 White

1/30 (3.3%)

5/68 (7.4%)

 Hispanic

2/30 (6.7%)

2/68 (2.9%)

 Other

1/30 (3.3%)

5/68 (7.4%)

Smoking

4/30 (13.3%)

13/68 (19.1%)

0.574

Fetal Sex (Male)

13/30 (43.3%)

38/68 (55.9%)

0.279

Sample GA (weeks)

21.05 (19.9–22.6)

39 (38.9–39.3)

< 0.001

Delivery GA (weeks)

38.8 (37.9–39.6)

39 (38.9–39.3)

0.34

 Transabdominal

30 (100%)

4/68 (6%)

< 0.001

 Cesarean delivery

0 (0%)

64/68 (94%)

Indication for amniocentesis

N/A

 Rule out Infection/ Inflammation

20 (66.7%)

 Karyotyping

12 (40%)^b

 Fetal lung maturity

3/67^a