Table 4. Measures of association extracted from eight studies on adverse birth outcomes and LD during or before pregnancy, positive LD serology during pregnancy, and surrogate measures of possible exposure to LD (e.g. tick bites or living in an endemic area).
(Significant odds ratios are bolded in the results.).
| Ref | Study | Adverse outcome definition | Diagnosis of LD or surrogate measure of exposure in mothers | OR* | 95% Conf. Interval | N | |
|---|---|---|---|---|---|---|---|
| Association with adverse birth outcomes due to having a positive LD serological test during pregnancy or history of gestational LD (GRADE ***) | |||||||
| [79] | Carlomagno (1988) | spontaneous miscarriage | Serological screening only (IgG) 2, 3 | 2.14 | 0.50 | 9.09 | 98 |
| [77] | Strobino (1993) | spontaneous miscarriage | Serological screening (IgG or IgM) 2, 4, 9 and clinical history of LD | 0.49 | 0.03 | 8.41 | 1521 |
| [77] | Strobino (1993) | spontaneous miscarriage | Clinical gestational LD 10 | 0.39 | 0.03 | 6.01 | 1746 |
| [77] | Strobino (1993) | spontaneous miscarriage | LD <1 year before conception | 1.73 | 0.69 | 4.36 | 1760 |
| [77] | Strobino (1993) | spontaneous miscarriage | LD >1 year before conception | 1.20 | 0.32 | 4.51 | 1752 |
| [78] | Dlesk (1989) | spontaneous miscarriage | Serological screening only (IgG or IgM)2, 3, 9 | 0.71 | 0.08 | 5.93 | 126 |
| [77] | Strobino (1993) | history of miscarriage | Serological screening (IgG or IgM) 2, 4, 9 and clinical history | 0.86 | 0.19 | 4.00 | 1521 |
| [80] | Bracero (1992) | premature rupture of membranes | Serological screening only (IgG or IgM)2,3, 9 | 1.01 | 0.12 | 8.88 | 134 |
| [80] | Bracero (1992) | premature labour | Serological screening only (IgG or IgM) 2,3, 9 | 1.46 | 0.16 | 13.10 | 134 |
| [80] | Bracero (1992) | low birth weight | Serological screening only (IgG or IgM) 2,3, 9 | 2.27 | 0.41 | 12.58 | 134 |
| [80] | Bracero (1992) | apgar <7 | Serological screening only (IgG or IgM) 2,3, 9 | 3.36 | 0.35 | 32.54 | 134 |
| [80] | Bracero (1992) | small for gestational age | Serological screening only (IgG or IgM) 2,3, 9 | 6.89 | 0.62 | 76.46 | 134 |
| [80] | Bracero (1992) | congenital abnormality, all1 | Serological screening only (IgG or IgM) 2,3, 9 | 5.62 | 0.21 | 150.06 | 134 |
| [81] | Strobino (1999) | congenital cardiac abnormality | History of LD 10 | 0.85+ǂ | 0.39 | 1.89 | 1500 |
| [77] | Strobino (1993) | congenital abnormality, all1 | Clinical gestational LD10 | 0.53ǂ | 0.07 | 4.16 | 1521 |
| [77] | Strobino (1993) | congenital abnormality, all1 | LD <1 year before conception | 1.65ǂ | 0.60 | 4.57 | 1760 |
| [77] | Strobino (1993) | congenital abnormality, all1 | LD > 1 year before conception | 2.94ǂ | 0.98 | 8.86 | 1752 |
| [77] | Strobino (1993) | congenital abnormality, minor1 | Clinical gestational LD10 | 0.80ǂ | 0.10 | 6.28 | 1521 |
| [82] | Williams (1995) | congenital abnormality, major 1 | LD before pregnancy | 3.26 | 0.75 | 14.20 | 2386 |
| [82] | Williams (1995) | congenital abnormality, all1 | LD before pregnancy | 1.13 | 0.26 | 4.85 | 2386 |
| [82] | Williams (1995) | congenital abnormality, major 1 | Clinical gestational LD10 | 6.80 | 0.78 | 59.00 | 2386 |
| [82] | Williams (1995) | congenital abnormality, all1 | Clinical gestational LD10 | 2.37 | 0.28 | 20.42 | 2386 |
| Association with adverse birth outcomes and an IgG or IgM positive cord blood serological test (GRADE **) | |||||||
| [83] | Williams (1988) | adverse birth outcomes | Cord blood serology (IgG) 5 | 0.40 | 0.05 | 3.07 | 255 |
| [82] | Williams (1995) | congenital abnormality, minor1 | Cord blood serology (IgG) 5 | 0.63 | 0.08 | 4.70 | 2386 |
| [84] | Lakos (2010) | adverse birth outcomes | Cord blood serology (IgG)6 | No est. | 74 | ||
| Association with congenital abnormalities and tick bites during pregnancy (GRADE **) | |||||||
| [82] | Williams (1995) | congenital abnormality, all1 | Tick bite during pregnancy | 1.63 | 0.77 | 3.47 | 2386 |
| [77] | Strobino (1993) | congenital abnormality, all1 | Tick bite during pregnancy | 1.35ǂ | 0.72 | 2.53 | 1731 |
| [82] | Williams (1995) | congenital abnormality, major 1 | Tick bite during pregnancy | 1.60 | 0.49 | 5.23 | 2386 |
| [77] | Strobino (1993) | congenital abnormality, major1 | Tick bite during pregnancy | 0.59ǂ | 0.14 | 2.49 | 1731 |
| [82] | Williams (1995) | congenital abnormality, minor1 | Tick bite during pregnancy | 1.62 | 0.64 | 4.11 | 2386 |
| [77] | Strobino (1993) | congenital abnormality, minor1 | Tick bite during pregnancy | 1.76ǂ | 0.90 | 3.46 | 1731 |
| [81] | Strobino (1999) | congenital cardiac abnormality | Tick bite during pregnancy | 0.93+ǂ | 0.56 | 1.56 | 1500 |
| Association with congenital abnormalities and a history (before or during pregnancy) of tick bites, but no LD (GRADE **) | |||||||
| [77] | Strobino (1993) | congenital abnormality, all1 | History of a tick bite with no LD8 | 1.46ǂ | 0.96 | 2.36 | 1731 |
| [77] | Strobino (1993) | congenital abnormality, major1 | History of a tick bite with no LD | 1.52ǂ | 0.75 | 3.07 | 1731 |
| [77] | Strobino (1993) | congenital abnormality, minor1 | History of a tick bite with no LD8 | 1.47ǂ | 0.87 | 2.49 | 1731 |
| Association with congenital abnormalities and mother residing in a LD endemic area compared to a non-endemic LD area (GRADE **) | |||||||
| [83] | Williams (1988) | congenital abnormality, all7 | Residence, endemic LD area | 0.90 | 0.49 | 1.65 | 421 |
| [82] | Williams (1995) | congenital abnormality, all1 | Residence, endemic LD area | 0.87ǂ | 0.70 | 1.06 | 4814 |
| [82] | Williams (1995) | congenital abnormality, major1 | Residence, endemic LD area | 1.08ǂ | 0.77 | 1.53 | 4814 |
| [82] | Williams (1995) | congenital cardiac abnormality | Residence, endemic LD area | 2.4ǂ | 1.25 | 4.59 | 4814 |
| [82] | Williams (1995) | congenital abnormality, minor1 | Residence, endemic LD area | 0.77ǂ | 0.60 | 0.99 | 4814 |
No est = no estimate is available because there were no events in either group.
*Odds Ratios were calculated from the raw data provided in the paper unless otherwise noted.
ǂ = Odds ratio extracted from the paper.
+ = Outcome was adjusted for other variables. [81] is adjusted for maternal age, number of live births, current county of residence, year of birth of study child, occupational x-ray exposure, maternal high blood pressure, and characteristics of residence (wooded area, deer) at the time of birth of the study child. Three studies reported a statistical analysis of the comparability of their exposed and control sampling frames, but did not present adjusted results [77,82,84].
1 Congenital abnormalities were summarized in some studies as all abnormalities together and then subdivided into minor abnormalities and major abnormalities.
2 Lyme disease serology was conducted in the first trimester.
3 Screening for LD positive serology in pregnant women included a single immunoassay.
4 Screening test was an immunoassay confirmed by an immunoblot.
5 Immunoassay used to screen cord blood
6 Immunoblot used to screen cord blood.
7 Study only sampled live births, so the impacts of LD that may lead to fetal demise would have been omitted from these results.
8 Results represent outcomes for women who had tick bites, but no LD. An association with tick bites is also presented for the same sample including women who had LD and for a subset of births where the physician records were available. The associations reported in the paper were conflicting for minor congenital abnormalities [77].
9 The serological test used in this study measured total IgG and IgM.