Nevi during pregnancy
Changes in dermoscopic pattern
Alterations in dermoscopic pattern of nevi during pregnancy mostly occur on the stretched skin areas (breast and abdomen) and predominantly within reticular nevi, where the pigment network simply becomes clearer and more widely meshed. The dermoscopic change of globular nevi is rather an increase in the number of brown globules on the periphery. Thinning and expanding of the skin during pregnancy may explain these alterations, where deep nests of nevi may be pushed closer to the surface, which leads to their appearance as junctional nests.  A dermoscopic analysis of nevi on pregnant women revealed following alterations of nevus pattern: Pigment networks thicken, becoming more prominent and globules of nevi with a globular pattern darken. One year after delivery, both of these changes regressed. This study also observed that reticular patterns of nevi become less organized, and globules distribution and size becomes less homogenous. Those changes persisted during the follow up after delivery. 
Nevi with peripheral globules
During pregnancy, as well as in young adolescence, nevi with peripheral globules are a common finding. One could argument with hormonal changes in both periods. Another explanation for the higher prevalence of nevi with peripheral globules among youth is its temporary nature and that these nevi transform into reticular or reticular-mixed patterns in older age. The finding of a similar anatomic site related distribution for the different types of nevi is in line with this hypothesis. 
Changes in size
The most important factor for the evaluation of nevi that change in size is the location on the body. Growth of nevi during pregnancy most often occurs on the front of the body, due to the stretched skin at this level. If not localized on stretched skin, nevi have not been shown to change significantly in size during pregnancy. 
Changes in pigmentation
In older literature, the change in pigmentation of nevi was explained by hormonal changes, present in pregnancy.  The causal molecular pathways are not well established yet, but the altered hormonal state of pregnancy may have several effects on melanocytic nevi. Increased levels of beta and alfa melanocyte-stimulating hormone, estrogen, progesterone, and beta-endorphin are believed to result in stimulation of melanocytes and therefore may cause hyperpigmentation during pregnancy. In a study using in vivo spectrophotometry to examine pigmentation,melanocytic nevi on the backs and lower legs of pregnant women were compared with nevi of non-pregnant women. The observed changes in pigmentation pattern did not reach significance level. Therefore, there is a lack of evidence for the assumption that moles darken during pregnancy.
Dysplastic nevus syndrome
Patients with dysplastic nevus syndrome were observed to have considerable clinical and histologic changes in nevi during pregnancy. Of 17 women included in a study by Ellis et al., 76% were observed to have clinical changes in nevi, which was a substantially higher percentage than the change in pregnant women without dysplastic nevus syndrome. Furthermore, the rate of clinical changes of nevi in dysplastic nevi syndrome was 3.9 times higher in pregnant women compared to non-pregnant women. Even in histology, the probability for dysplasia was twice as high in pregnant women with dysplastic nevus syndrome.
Biopsy during pregnancy
Based on the available evidence, changes that occur in a nevus during pregnancy may not be underestimated as a regular consequence of pregnancy. Changes of nevi in pregnant women should be evaluated just as in non-pregnant patients and a required diagnostic biopsy should not be delayed until after pregnancy.  Lidocaine can be safely used for local anesthesia during pregnancy, thus there is no need to delay executing a biopsy on a suspicious melanocytic lesion. 
- Bieber et al.: Nevi and pregnancy. J. Am. Acad. Dermatol. 2016;75:661-6. PMID: 27646736. DOI.
- Strumia: Digital epiluminescence microscopy in nevi during pregnancy. Dermatology (Basel) 2002;205:186-7. PMID: 12218242. DOI.
- Aktürk et al.: Dermoscopy is a suitable method for the observation of the pregnancy-related changes in melanocytic nevi. J Eur Acad Dermatol Venereol 2007;21:1086-90. PMID: 17714130. DOI.
- Zalaudek et al.: Frequency of dermoscopic nevus subtypes by age and body site: a cross-sectional study. Arch Dermatol 2011;147:663-70. PMID: 21690528. DOI.
- Zampino et al.: Are melanocytic nevi influenced by pregnancy? A dermoscopic evaluation. Dermatol Surg 2006;32:1497-504. PMID: 17199661. DOI.
- Parmley & O'Brien: Skin changes during pregnancy. Clin Obstet Gynecol 1990;33:713-7. PMID: 2289337.
- Tyler: Physiological skin changes during pregnancy. Clin Obstet Gynecol 2015;58:119-24. PMID: 25517755. DOI.
- Ellis: Pregnancy and sex steroid hormone effects on nevi of patients with the dysplastic nevus syndrome. J. Am. Acad. Dermatol. 1991;25:467-82. PMID: 1918487.
- Gormley: Cutaneous surgery and the pregnant patient. J. Am. Acad. Dermatol. 1990;23:269-79. PMID: 2212124.
- Ralston & Shnider: The fetal and neonatal effects of regional anesthesia in obstetrics. Anesthesiology 1978;48:34-64. PMID: 339784.