妊娠间隔对妊娠结局影响的研究进展

妊娠间隔过短或者过长均会导致妊娠不良结局的增加,也会导致妊娠期糖尿病、子痫前期和胎儿近期或远期并发症的增加。目前对于最佳妊娠间隔范围还没有统一的结论,多数研究给出的最佳范围在18～60个月。而妊娠间隔对妊娠结局的作用受多种因素的干扰,如孕次、孕周、年龄、前次妊娠史、受孕方式、社会经济因素等。目前妊娠间隔对妊娠结局影响作用机制的假说,较多的认为是过短妊娠间隔是由于母体体内物质缺乏所致,而过长妊娠间隔则是机体的衰老等因素共同影响所致,但相关临床及基础研究均较少,仍需要更多的研究进行阐释。     

双胎妊娠分娩时机选择的多中心回顾性分析

目的 降低双胎妊娠围产儿不良预后的发生率，探讨合理的双胎终止妊娠时间。方法 对1993年1月到2003年10月十年期间在上海地区六家医院妇产科分娩的655例双胎妊娠进行回顾性分析，分别计算出各孕周大小胎儿出生体重的百分位数、小于孕龄儿（small for gestational age，SGA）和重度窒息的发生率。结果 1．整个孕期双胎妊娠中小胎儿出生体重的第50百分位数均明显落后于单胎胎儿，33周前大胎儿出生体重的第50百分位数与单胎胎儿接近，33周后差别逐渐增大，39周后大小胎儿出生体重与单胎相比差别更为显著。与单胎妊娠不同，双胎妊娠大胎儿在39周、小胎儿40周达最大出生体重（3073g和2670g），在此之后出生体重反而下降，41周时明显降低（2555g和2303g，P〈0．05）。2．双胎妊娠大小胎儿SGA发生率随孕龄的增加呈上升趋势，39周后上升幅度明显增加，41周达到最高（P〈0．05）。3．39周后小胎儿重度窒息的发生率明显增加。结论 39周后双胎妊娠胎儿出生体重呈下降趋势，SGA及小胎儿围产期重度窒息的发生率明显上升，因此双胎妊娠的分娩时间不应超过39周。     

不同的妊娠间隔时间与高龄经产妇妊娠结局的关系

目的:探讨高龄经产妇不同妊娠间隔时间与妊娠结局(妊娠合并症、分娩并发症、新生儿窒息)的关系。方法:收集2019年1月至2020年6月在赣州市人民医院进行产前检查的高龄经产妇(其预产期年龄≥35岁) 205例作为研究对象。根据距上次妊娠间隔时间进行分组:A组(2～5年)97例、B组(6～9年) 63例、C组(≥10年) 45例。收集孕妇妊娠合并症、分娩方式、产程长短、分娩并发症、新生儿转科率及Apgar评分。比较各组妊娠结局的差异,以A组为对照,二分类Logistic回归分析评价妊娠间隔时间长短发生不同妊娠结局的风险。ROC曲线评估妊娠间隔时间预测发生不同妊娠结局的敏感性。结果:(1)A组、B组、C组经产妇的妊娠合并症、分娩并发症、第一产程时间、新生儿转科率和新生儿窒息程度整体上存在显著差异,A组不良妊娠结局的发生率最低,随妊娠间隔时间的延长,不良妊娠结局的发生率逐渐升高。(2)以A组作为参照,B组和C组发生妊娠期高血压、妊娠期糖尿病、胎膜早破、胎盘早剥、产后出血、羊水污染、新生儿窒息等结局的风险明显增加(P <0.05);加入年龄去除混杂因素后,与A组相比,B组发生胎膜早破(OR 2.35,95%CI 1.83～5.25,P=0.021)、胎盘早剥(OR 6.77,95%CI 3.46～12.73,P=0.000)的风险明显增加,C组发生妊娠期糖尿病(OR 3.86,95%CI 1.33～7.36,P=0.001)、胎膜早破(OR=6.92,95%CI 3.47～11.56,P=0.000),胎盘早剥(OR 12.88,95%CI 4.67～18.28,P=0.000)和新生儿窒息(OR4.82,95%CI 1.37～6.59、P=0.012)的风险显著增加。(3)ROC曲线表明,不同妊娠间隔时间预测发生妊娠期糖尿病、胎膜早破、胎盘早剥、新生儿窒息的敏感度分别为AUC=0.708,95%CI0.677～0.803; AUC=0.651,95%CI 0.556～0.683; AUC=0.606,95%CI 0.521～0.647; AUC=0.721,95%CI 0.681～0.788。结论:高龄孕妇发生不良妊娠结局的风险随着妊娠间隔时间的延长而逐渐增高。长妊娠间隔(6～9年、≥10年)是发生妊娠期糖尿病、胎膜早破、胎盘早剥、新生儿窒息的独立危险因素。     

超高龄经产妇妊娠并发症及妊娠结局的调查研究

目的:探讨超高龄经产妇围生期妊娠并发症及妊娠结局的特点,为临床上预防高龄经产妇围生期不良结局提供指导。方法:选取北京市朝阳区、海淀区6家助产机构2016年11月—2017年2月分娩的经产妇,按照产妇年龄分为超高龄经产妇组(≥40岁)198例、一般高龄经产妇组(35~39岁)1 110例、非高龄经产妇组(<35岁)1 645例,对其一般人口学资料、妊娠合并症和并发症及新生儿健康状况等进行横断面调查,比较不同组别产妇妊娠并发症和不良妊娠结局的差异。结果:①超高龄经产妇组和一般高龄经产妇组选择剖宫产的比例比非高龄经产妇组高,分别为27.3%,22.1%和16.8%,差异有统计学意义(均P ′<0.017)。超高龄经产妇组的分娩孕周比非高龄经产妇组小,差异有统计学意义(P ′<0.017)。②校正了孕期增重、分娩方式、胎数和分娩孕周等影响因素之后,超高龄经产妇组发生妊娠期高血压、妊娠期糖尿病、产后出血、多次(≥2次)流产的风险高于非高龄经产妇组,OR值分别为3.70,1.98,1.74,3.44,均有统计学意义(均P<0.05);发生甲状腺疾病(甲减、亚甲减或甲亢)的风险低于非高龄经产妇组(OR=0.40,P=0.032);胎盘相关疾病和危重症2组比较差异无统计学意义。一般高龄经产妇发生妊娠期高血压、妊娠期糖尿病、多次(≥2次)流产的风险高于非高龄经产妇组,OR值分别为1.92,1.57,1.76,均有统计学意义。③超高龄经产妇组新生儿转入新生儿重症监护病房(NICU)、发生新生儿呼吸窘迫综合征(NRDS)的风险高于非高龄经产妇组,OR值分别为2.11和4.28,有统计学意义。一般高龄经产妇组新生儿发生NRDS的风险高于非高龄经产妇组(OR=2.11),有统计学意义。结论:超高龄经产妇发生妊娠不良结局的风险高于非高龄经产妇,对有可能成为超高龄产妇的育龄妇女,孕前应充分评估身体健康状况,加强孕前健康管理,对已妊娠的超高龄经产妇应严格进行围生期的随访和管理,以减少不良妊娠结局的发生。     

辅助生殖技术对妊娠结局和子代出生结局的影响分析

目的 探究辅助生殖技术（ART）对妊娠结局和子代出生结局的影响。方法 回顾性分析本院生殖中心收治的600例有生育需求者的病历资料,按其受孕方式分为对照组（自然妊娠,300例）及研究组（ART,300例）,比较两组有生育需求者的妊娠结局及子代出生结局。结果 研究组多胎率、流产率、剖宫产率分别为11.67%、17.00%、50.33%,均高于对照组的2.00%、7.33%、22.67%,差异有统计学意义（P<0.05）。两组子代先天性心脏病率、畸胎率比较,差异无统计学意义（P>0.05）;研究组子代早产儿率为19.00%,高于对照组的5.00%,差异有统计学意义（P<0.05）。结论 ART的问世为不孕夫妻带来了生育希望,但孕妇流产率、剖宫产率及子代早产率相对自然妊娠者更高,临床需加大产前管理和妊娠并发症防治工作的力度。     

经产妇孕期增重及妊娠结局的调查分析

目的:探讨经产妇孕期增重及妊娠结局情况,为孕期保健指导提供依据。方法:回顾分析镇江市妇幼保健院2015年1月至12月分娩的3801例单胎产妇,比较经产妇与初产妇的年龄、孕龄、孕前体重、孕期增重(GWG)、分娩信息等临床资料。结果:经产妇的年龄、孕次、孕前BMI、新生儿体重高于初产妇,孕龄、GWG低于初产妇(P均0.05)。经产妇巨大儿和早产的发生率高于初产妇(P均0.05)。孕前高体重产妇(孕前BMI≥24.0kg/m2)中,经产妇GWG达标率高于初产妇(P0.05)。孕前正常体重的产妇(18.5kg/m2≤BMI24.0kg/m2)中,经产妇低体重儿、早产发生率高于初产妇(P均0.05)。结论:经产妇不良妊娠结局发生率较高,需做好孕期保健指导,应重点关注体重管理。     

妊娠合并肝功能损害对妊娠结局的影响

目的探讨妊娠合并肝功能损害(妊娠肝损)对妊娠结局的影响.方法分析比较了80例妊娠肝损患者及同期随机抽查的56例非肝损患者(对照组)的临床资料.结果肝损组新生儿体重、分娩孕周均显著低于对照组(P＜0.05);肝损组羊水污染率明显高于对照组(P＜0.05),肝损组新生儿窒息率高于对照组,但无统计学差异;肝损组血ALT＞500nmoL@S-1/L患者与ALT＜500nmoL@S-1/L的患者相比,早产儿发生率明显增加(P＜0.05).结论妊娠肝损可影响新生儿的体重,且羊水污染机会明显增加,积极正确的处理可以使肝损患者安全度过围产期并能提高围生儿的生存质量.     

单绒毛膜三羊膜囊三胎的妊娠结局及减胎术对其的影响

目的:总结单绒毛膜三羊膜囊（monochorionic triamniotic, MCTA）三胎的妊娠结局及减胎术对其的影响。方法:回顾性纳入2012年1月1日至2020年1月1日于北京大学第三医院分娩的23例MCTA三胎病例,均于早孕期在本院产前检查,根据孕妇是否接受减胎分为选择性减胎组（随机减去一胎保留双胎,8例）...     

体外受精-胚胎移植重复周期助孕结局的回顾性分析

目的：研究体外受精-胚胎移植（IVF-ET）多次助孕周期妊娠结局的变化趋势,探讨影响重复周期妊娠结局的相关因素。方法：回顾性分析中山大学孙逸仙纪念医院生殖中心2008年1月—2009年10月行IVF/胞浆内单精子注射（ICSI）助孕治疗的患者1314例（1746周期）,其中助孕周期次数≥3的患者128例（191周期）。分析妊娠结局与助孕周期次数的关系,比较第3周期未妊娠者（A组,68例）与妊娠者（B组,37例）既往未妊娠周期中相关指标的差异。结果：临床妊娠率、活产率在第1～4周期间呈现递减趋势（P〈0.001）,第1周期临床妊娠率显著高于第2周期,活产率显著高于第2～4周期,但第2周期及其后周期间临床妊娠率、活产率差异无统计学意义（P〉0.05）。Logistic回归分析第1/2周期中有统计学意义的变量为年龄、不孕类型和优质胚胎个数,其OR值分别为0.757/0.865、12.00/3.376和1.711/1.436。结论：IVF-ET第1周期临床妊娠率和活产率高,其后周期临床妊娠率、活产率与周期次数无明显关系。在第1、2周期未妊娠的患者中,年龄越小、优质胚胎数越多和继发不孕者在第3周期中获得妊娠的可能性越大。     

子宫内膜异位症在辅助生育中对妊娠结局影响的研究进展

子宫内膜异位症(endometriosis,EMs)对生育能力的影响原因是多种的,机制是叠加的,辅助生育技术改善了EMs患者的生育能力,但内异症也影响着辅助生育的妊娠结局。本文就近年有关EMs导致不育和反复流产的病理生理研究进展及合并内异症患者对辅助生育技术中妊娠结局的影响等方面做一综述,以提高对EMs对生育能力影响的认识,达到进一步改善诊治方法,提高妊娠率、减少自然流产率、降低妊娠并发症的目的。     

Effects of interpregnancy interval and outcome of the preceding pregnancy on pregnancy outcomes in Matlab, Bangladesh

Objective  To estimate the effects on pregnancy outcomes of the duration of the preceding interpregnancy interval (IPI) and type of pregnancy outcome that began the interval.
Design  Observational population-based study.
Setting  The Maternal Child Health–Family Planning (MCH–FP) area of Matlab, Bangladesh.
Population  A total of 66 759 pregnancy outcomes that occurred between 1982 and 2002.
Methods Bivariate tabulations and multinomial logistic regression analysis.
Main outcome measures  Pregnancy outcomes (live birth, stillbirth, miscarriage [spontaneous fetal loss prior to 28 weeks], and induced abortion).
Results  When socio-economic and demographic covariates are controlled, of the IPIs that began with a live birth, those <6 months in duration were associated with a 7.5-fold increase in the odds of an induced abortion (95% CI 6.0–9.4), a 3.3-fold increase in the odds of a miscarriage (95% CI 2.8–3.9), and a 1.6-fold increase in the odds of a stillbirth (95% CI 1.2–2.1) compared with 27- to 50-month IPIs. IPIs of 6–14 months were associated with increased odds of induced abortion (2.0, 95% CI 1.5–2.6). IPIs ≥ 75 months were associated with increased odds of all three types of non-live-birth (NLB) outcomes but were not as risky as very short intervals. IPIs that began with a NLB were generally more likely to end with the same type of NLB.
Conclusions  Women whose pregnancies are between 15 and 75 months after a preceding pregnancy outcome (regardless of its type) have a lower likelihood of fetal loss than those with shorter or longer IPIs. Those with a preceding NLB outcome deserve special attention in counselling and monitoring.     

Effect of interpregnancy interval on outcomes of pregnancy after recurrent pregnancy loss

Abstract

Objective: To examine the effect of interpregnancy interval (IPI) on outcomes of pregnancy after recurrent pregnancy loss (RPL).

Methods: A retrospective cohort study including 325 patients treated at a RPL clinic, with two or more consecutive pregnancy losses followed by a subsequent (index) pregnancy, of whom 163 had IPI?≤?6 months, and 212 had IPI?>?6 months.

Results: Pregnancy loss rate in the index pregnancy was positively associated with increased IPI (18.6% in women with IPI?≤?6 months, and 29.7% in women with IPI?>?6 months; p?=?0.029). In a multivariable logistic analysis, excluding women with fertility problems, and adjusting for maternal age and ethnicity, the OR for pregnancy loss rate for IPI longer than 6 months compared to shorter IPI was 1.76 (95%CI: 0.96–3.22, p?=?0.067).

Conclusions: Our results suggest that IPI shorter than 6 months, in women with no fertility problems, is associated with lower rate of subsequent miscarriage. Further studies are needed to substantiate this finding.     

自然流产后再次妊娠间隔时间的探讨

目的 探讨自然流产后再次妊娠的间隔时间是否影响围产结局。方法 对自然流产后12个月内再次妊娠的102例孕妇进行回顾性调查，两次妊娠间隔时间≤3个月者为28例(≤3月组)，间隔时间＞3月者74例(＞3月组)，比较两组围产结局。结果 两组前置胎盘、早产和胎膜早破的发生率(3．6％与4．0％，3．6％与10．8％，17．8％与14．9％)差异无显著性(P＞0．05)，两组阴道分娩、产钳助产和剖宫产率差异无显著性(P＞0．05)，≤3月组低体重儿、巨大儿和1 min Apgar评分≤7分的发生率分别为3．6％、10．7％和3.6％，与＞3月组(5．4％、9．4％和6．7％)比较，差异无显著性(P＞0．05)。≤3月组无一例新生儿转入重症监护室、出生缺陷和死亡，而＞3月组有6例新生儿转入重症监护室，2例出生缺陷，1例新生儿死亡。结论 自然流产后再次妊娠的间隔时间可能对围产结局没有影响。     

Influence of pregnancy outcome on subsequent pregnancy

In this study to determine the harmful effect of abnormal pregnancy outcome on the immediately following pregnancy, 573 recently delivered women (with 2347 pregnancies) were interviewed. Data were recorded on their pregnancy outcomes (normal, abortion, stillbirth and congenital malformation), as well as on their interpregnancy intervals. A significant difference was found between the chances of having a spontaneous abortion following a normal outcome (5.5%) against that following a spontaneous abortion (31.1%). Also, the chances of a normal outcome following a normal outcome were 92.4%, compared with 63.9% following a spontaneous abortion. The delivery of a malformed baby is associated with a larger proportion of abortion and congenital malformation in the subsequent pregnancy, while stillbirth was followed by a larger proportion of abortion and stillbirth. A longer interpregnancy interval did not appear to have any protective effect on the subsequent pregnancy.     

双胎输血综合征患者的围产结局分析

目的 探讨双胎输血综合征患者的围产结局分析.方法 选择2002年11月1日-2005年9月30日在北京妇产医院住院分娩的双胎妊娠孕妇352例,其中合并双胎输血综合征(TTTS)的24例患者及其双胎儿为TTTS组,不合并TTTS的328例患者及其双胎儿为对照组,比较两组围产结局;比较对照组中单卵双胎与TTTS组的母儿预后差异;比较TTTS组中供血儿和受血儿的预后差异;探讨TTTS分级对围产结局的影响;按照2004年Bajoria提出的诊断标准进行TTTS的诊断和分级.结果 (1)TTTS发生率:TTTS的发生率为6.8%(24/352).(2)合并症及并发症:TTTS组羊水过多[37.5%(9/24)]、妊娠期高血压疾病[20.8%(5/24)]和早产[66.7%(16/24)]的发生率明显高于对照组[分别为2.1%(7/328)、7.0%(23/328)、36.3%(119/328)],两组比较,差异有统计学意义(P＜0.05).(3)围产儿结局:TTTS组围产儿胎死宫内[18.8%(6/32)]、新生儿窒息[73.1%(19/26)]、转入新生儿ICU[88.5%(23/26)]、新生儿死亡[15.4%(4/26)]和围产儿死亡的发生率[31.3%(10/32)]也明显高于对照组[分别为1.1%(7/640)、3.0%(19/632)、23.4%(148/632)、1.7%(11/632)、2.8%(18/632)],两组比较,差异均无统计学意义(P＞0.01).(4)与对照组中单卵双胎患者的合并症及并发症比较:TTTS组妊娠期高血压疾病和早产的发生率明显高于对照组中单卵双胎[分别为9.9%(14/142)和49.3%(70/142)],两者比较,差异均无统计学意义(P＞0.05).(5)与对照组中单卵双胎围产儿结局比较:TTTS组围产儿胎死宫内、新生儿窒息、转入新生儿ICU、新生儿死亡和围产儿死亡率均明显高于对照组中单卵双胎[分别为0.7%(2/282)、3.9%(11/280)、29.3%(82/280)、2.1%(6/280)、3.2%(8/282)],差异均有统计学意义(P＜0.01).(6)TTTS分级对围产结局的影响:TTTS Ⅰ～Ⅲ级者的围产结局优于Ⅳ～Ⅴ级者,但差异无统计学意义(P＞0.05).结论 双胎妊娠合并TTTS患者的围产结局不良,应及早诊治.     

2 486例妊娠期高血压疾病患者的临床分析

目的了解近年来南方医科大学附属深圳妇幼保健院收治的妊娠期高血压疾病患者的发病趋势、并发症情况及对妊娠结局的影响。 方法回顾性分析2009年1月至2013年12月在南方医科大学附属深圳妇幼保健院就诊并分娩的2 486例妊娠期高血压疾病患者的临床资料,包括发病率、孕妇年龄、住院天数、分娩方式、流动人口比例及母婴并发症等。 结果5年间我院重度子痫前期发生率呈现下降趋势,从2009年的1.74%降至2013年的1.34%(χ²＝12.321,P<0.05);流动人口所占比例较高(46.46%);分娩方式仍然以剖宫产为主(74.09%),高于阴道分娩(21.44%),(χ²＝736.084,P<0.001)。妊娠期高血压疾病孕妇严重并发症的构成依次是：产后出血、胎盘早剥、HELLP综合征、心功能不全、弥散性血管内凝血、急性肾衰竭、脑血管意外;其围产儿严重并发症的构成依次为：早产、胎儿生长受限、新生儿窒息、死胎、流产。 结论妊娠期高血压疾病仍是威胁孕产妇以及围产儿健康的严重疾病,必须加强产前保健,早发现、早诊断和早治疗,以改善母婴妊娠结局。     

The effects of screening and intervention of subclinical hypothyroidism on pregnancy outcomes: a prospective multicenter single-blind,randomized, controlled study of thyroid function screening test during pregnancy

Purpose: To evaluate the effect of subclinical hypothyroidism (SCH) screening and intervention on pregnancy outcomes and explore the significance of thyroid function during early pregnancy.

Methods: Pregnant women were recruited from Peking Union Medical College Hospital (screening group for measuring thyroid function and thyroid antibody in early pregnancy) and Haidian Maternal & Child Health Hospital (control group whose serum was stored and measured shortly after delivery) from July 2011 to December 2012. Thyrotropin levels 2.5–10?mIU/L and free T4 levels in normal range were considered SCH. Some of the screening group were treated with levothyroxine and adjusted. The others did not take medicine but kept a regular follow-up visit to doctors after antenatal clinic. The pregnancy outcomes and complications were compared.

Results: 1671 women (675 in screening group and 996 in control group) were recruited. 419 (167 from screening group) women was diagnosed as SCH. In screening group, 105 SCH and 4 hypothyroid women received thyroid hormone replacement therapy. The miscarriage and fetal macrosomia risks were lower, and cesarean was higher in screening group than control.

Conclusion: Screening and intervention of SCH can significantly reduce the incidence rate of miscarriage.     

Idiopathic polyhydramnios at term and pregnancy outcomes: a multicenter observational study

Aim: To assess pregnancy outcomes in pregnancies with idiopathic polyhydramnios at term.

Methods: We conducted a retrospective cohort study of 106 225 term pregnancies from 37 hospitals in China. Maternal and fetal outcomes in pregnancies with idiopathic polyhydramnios were compared with pregnancies with normal amniotic fluid. The primary outcome was intra-uterine fetal death (IUFD).

Results: In all, 307 out of 106?225 (0.3%) had idiopathic polyhydramnios at term, 276 of which were mild and 31 of which were moderate-severe. Compared to term pregnancies with normal amniotic fluid, pregnancies idiopathic polyhydramnios was associated with over 24-fold higher risk for IUFD (adjusted odds ratio [aOR] 24.4, 95% confidence interval (CI) 7.3–82.0), macrosomia (aOR 2.8, 95%CI 2.0–3.8), malpresentation (aOR 2.5, 95%CI 1.7–3.7), cesarean delivery (aOR 2.5, 95%CI 1.7–3.7) and low APGAR scores at 5?min (aOR 4.3, 95%CI 2.4–7.8), which increased with severity of idiopathic polyhydramnios.

Conclusion: Term pregnancies with idiopathic polyhydramnios, especially moderate–severe ones are at a significantly increased rate for adverse pregnancy outcome. Increased antepartum surveillance of fetal well-being and timed delivery are warranted.     

Substance abuse during pregnancy: effect on pregnancy outcomes

Objective

To determine the contribution of drug use to maternal and perinatal complications, controlling for social confounders.

Study design

This is a retrospective cohort study of 247 drug-using women and 741 controls over a 4-year period from 1997 to 2000. Cases were identified from the drug dependency register. Three controls for each woman with substance abuse were selected from the delivery suite records, with calliper matching by year of delivery (any control patient who delivered within 6 months before or after the date of delivery of a drug-using woman was considered as a potential match) and district of residence (post code). The primary outcomes of interest were preterm birth, abruption, pre-eclampsia, intrauterine growth restriction and low birth weight.

Results

There were statistically significantly more preterm births amongst drug-using women (relative risk (RR) 2.5, 95% confidence interval (CI) 1.6–3.8), with preterm births complicating 25% of births amongst drug users. The incidence of low birth weight was 30.8% amongst drug-using women compared to 8% in control women (RR 3.6, CI 2.4–5.4), and the incidence of growth restriction was 25%, significantly higher than the control group (RR 3.82, CI 2.4–6.1). The risk of abruption was also higher (RR 2.74, CI 1.1–7.0). Of note is the extremely low incidence of pre-eclampsia among drug users, even after controlling for the confounder effects of parity and smoking.

Conclusions

Despite multidisciplinary co-ordinated antenatal care, women with substance abuse during pregnancy are at significant risk of adverse obstetric and perinatal outcome, controlling for social confounders. A limitation of the study is that the sample size was not large enough to clearly assess individual drugs. This is the first study to highlight low incidence of pre-eclampsia among drug users over and above the effect of smoking. Further research is needed to elucidate the underlying biological reason for the lack of pre-eclampsia in women with substance abuse during pregnancy.